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Biomedical subjects

A J Morris

Publications and source records attributed to A J Morris.

At least 163 records · Page 9Linked to original sources
PubMed1995

Laboratory and clinical evaluation of Mycobacterium xenopi isolates.

Mycobacterium xenopi and Mycobacterium avium complex (MAC) are biochemically similar. To define the laboratory characteristics of M. xenopi that distinguish it from MAC, 53 M. xenopi isolates from different areas in the United States and 47 isolates recovered at one hospital were evaluated by 13 biochemical tests, AccuProbe MAC (Gen-Probe, Inc., San Diego, CA, USA), colony morphology, formation of X-colonies, pigmentation in response to light, growth on MacConkey agar without crystal violet, and relative growth rates at 25 degrees C, 36 degrees C, and 45 degrees C on solid media. Relative growth rates of 10 M. xenopi and 11 MAC isolates were measured at 25 degrees C, 36 degrees C, and 42 degrees C in Middlebrook broth processed using the BACTEC TB System. Ten M. xenopi were tested for p-nitro-alpha-acetylamino-beta-hydroxypropiophenone inhibition at 36 degrees C and 42 degrees C. Reevaluation of 81 isolates previously identified as MAC by biochemical tests alone revealed that two were M. xenopi. The most reliable characteristics distinguishing M. xenopi from MAC were the presence of X-colonies (M. xenopi 97% vs MAC 1%), positive 3-day arylsulfatase (M. xenopi 88% vs MAC 1%), growth at 25 degrees C (M. xenopi 0% vs MAC 100%), and AccuProbe MAC test results (M. xenopi 0% hybridized). Retrospective chart review of 37 patients using American Thoracic Society criteria revealed that six (16%) patients had clinically important isolates. At one of our hospitals M. xenopi was the second most common mycobacterial species isolated for 1990-1992, accounting for 27% of all isolates, whereas at our other hospital it accounted for 1% of isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS-Related Opportunistic Infections↗
PubMed1995

Concentration of enzyme-dependent activation of PLC-beta 1 and PLC-beta 2 by G alpha 11 and beta gamma-subunits.

Differential regulation of PLC-beta 1 and -beta 2 by the G-protein alpha-subunit, G alpha 11, and by G-protein beta gamma-subunits was studied utilizing recombinant PLC-beta 1 and -beta 2. Rat PLC-beta 1 and human PLC-beta 2 were purified after recombinant baculovirus-mediated expression in Sf9 cells. The catalytic properties of the purified recombinant isoenzymes were directly compared to PLC-beta 1 purified from bovine brain and PLC-beta 2 partially purified from HL60 polymorphonuclear neutrophils. The recombinant isoenzymes were indistinguishable from the native isoenzymes with respect to dependence of reaction velocity on bulk PtdIns(4,5)P2 substrate concentration, pH, and free Ca2+ concentration. Marked AlF(4-)-dependent activation was observed upon reconstitution of rPLC-beta 1 with the G-protein alpha-subunit, G alpha 11. Activation occurred with a concentration dependence on G alpha 11 for activation and elevation in reaction velocity that was similar to that of native PLC-beta 1. In contrast, G alpha 11 promoted only a small elevation in the catalytic rate of recombinant PLC-beta 2, which was also typical of the native isoenzyme. Maximal reaction rates with respect to PLC-beta isoenzyme concentration were achieved and indicated that rPLC-beta 2 required 10-fold greater concentrations of both G alpha 11 and of rPLC-beta 2 for activation than did rPLC-beta 1. rPLC-beta 1 and rPLC-beta 2 were also differentially regulated by beta gamma-subunits. This differential activation was not the result of different concentration dependencies on beta gamma-subunit for activation, but rather, the result of the greater degree to which the catalytic rate of PLC-beta 2 was elevated by beta gamma-subunits when compared to PLC-beta 1.

Animals↗
PubMed1995

Clinical impact of bacteria and fungi recovered only from broth cultures.

We prospectively evaluated 356 bacteria and fungi recovered from broth enrichment tubes from cultures with sterile direct plates to determine the clinical impact of isolates recovered only from broth cultures. These "broth only" isolates (BOI) were classified as contaminants or true on the basis of review of patient charts. True isolates were considered clinically relevant only if they altered or should have altered patient management. Of 356 BOI, 259 (73%) were considered contaminants (mostly coagulase-negative staphylococci and Propionibacterium spp.) and 97 (27%) were considered true. For individual microorganisms, 9 of 9 (100%) Staphylococcus aureus isolates, 13 of 13 (100%) members of the family Enterobacteriaceae, 10 of 12 (83%) fungi, 7 of 10 (70%) enterococci, 7 of 11 (64%) other gram-negative bacilli, 13 of 31 (45%) anaerobic bacteria, 10 of 24 (42%) streptococci, 22 of 140 (16%) coagulase-negative staphylococci, 6 of 92 (7%) Propionibacterium spp., and 0 of 14 (0%) diphtheroids and Bacillus spp. were classified as true. Eleven of 97 (11%) patients with true BOI had clinically relevant isolates. Fifty-nine of the 97 (61%) patients with true isolates already were on therapy, and no change was made because of the BOI. Six (6%) patients with contaminants received therapy for their BOI. We conclude that broth inoculated as an adjunct to direct plating seldom yields results that favorably alter patient management and could be omitted for most specimens without compromising patient care.

Adult↗
PubMed1995

Regulation of phosphoinositide-3-kinase by G protein beta gamma subunits in a rat osteosarcoma cell line.

Rat osteosarcoma 17/2.8 cells (Ros 17/2.8 cells) were labeled with [32P]PO4(2-), and their levels of inositol lipids were determined after stimulation with thrombin. Thrombin stimulated a pertussis toxin-sensitive rapid accumulation of phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P3] with lesser increases in levels of phosphatidylinositol-3,4-bisphosphate [PtdIns(3,4)P2] and phosphatidylinositol-3-phosphate [PtdIns3P] that were slower in onset. Ros 17/2.8 cell homogenates contained phosphatase activities that hydrolyzed PtdIns(3,4,5)P3 to PtdIns(3,4)P2 and PtdIns3P. Phosphoinositide-3-kinase activity was determined in Ros 17/2.8 cell homogenates using exogenously provided PtdIns(4,5)P2. Guanosine-5'-3-O-(thio)triphosphate caused an approximately 3-fold increase in phosphoinositide-3-kinase activity in a manner that was blocked by high concentrations of guanosine-5'-2-O-(thio)diphosphate. Purified bovine brain G protein beta gamma subunits also increased phosphoinositide-3-kinase activity modestly in Ros 17/2.8 cell homogenates. Ros 17/2.8 cell homogenates contained phosphatase activities that sequentially dephosphorylated PtdIns(3,4,5)P3 to PtdIns(3,4)P2 and PtdIns3P. Two peaks of phosphoinositide-3-kinase activity were resolved by anion exchange chromatography of a Ros 17/2.8 cell cytosolic extract. The later elution of these was selectively activated by beta gamma subunits (16-fold activation with 16 microM beta gamma subunits). Half-maximal effects of the beta gamma subunits were observed at a concentration of 0.6 microM, and activation was blocked by preincubation of the beta gamma subunits with an excess of recombinant Gi alpha 2. beta gamma Subunits did not activate the p85 alpha/p110 beta form of phosphoinositide-3-kinase purified from sf9 cells after expression with the use of baculovirus vectors.

Animals↗
PubMed1995

Differences in epidemiological findings when changing from the Anglepoise desk lamp to the Daray Versatile Medical Light.

The effect on epidemiological findings arising from changing from an Anglepoise desk lamp to a Daray Versatile Medical Light was studied using 155 school children aged between 11 and 14 years. The children were examined on separate days using the two types of illumination. Differences observed in DMFT, sealed teeth, gingival health, plaque and calculus were not significant. The mean DT (+/- SE) was 0.12 (+/- 0.03) for the Anglepoise desk lamp and 0.16 (+/- 0.04) for the Daray Versatile Medical Light, the difference between these values being significant (P < 0.05). The magnitude of the difference was small (0.04 DT, SE +/- 0.02) when compared with observed changes in the mean DT in 15-year-old children in the districts where the study took place between 1986 and 1990. The level of agreement ranged from very good (kappa = 0.81-1.00) for DMFT and components to fair for plaque (kappa = 0.32). It is concluded that there is no evidence from this study that changing the type of illumination from Anglepoise desk lamp to Daray Versatile Medical Light would affect markedly the results of dental prevalence surveys.

Adolescent↗
PubMed1994

Lysine-146 of rabbit muscle aldolase is essential for cleavage and condensation of the C3-C4 bond of fructose 1,6-bis(phosphate).

Lysine-146 of rabbit muscle aldolase (D-fructose-1,6-biphosphate aldolase, EC 4.1.2.13) is absolutely conserved in class I (Schiff base) aldolases and has been implicated previously in catalysis by protein modification. Site-directed mutagenesis was used to change lysine-146 to alanine, glutamine, leucine, or histidine, creating the mutant enzymes K146A, K146Q, K146L, and K146H, respectively. These mutant proteins were expressed at high levels in bacteria and were purified by substrate affinity elution from CM-Sepharose, the same method that is used for the wild-type enzyme. The mutants K146A, K146Q, and K146L had substrate cleavage rates below standard detection levels. Modified cleavage assays indicated that these enzymes were (0.5-2) x 10(6)-fold decreased in the rate of catalysis of fructose 1,6-bis(phosphate) (Fru-1,6-Pa)cleavage. The K146H enzyme, however, was approximately 2000-fold slower than wild type in the rates of both cleavage and condensation of Fru-1,6-P2. In assays for the presence of enzymatic intermediates, all of the mutant enzymes were able to catalyze formation of the carbanion intermediate with dihydroxyacetone phosphate, whereas this intermediate was below the level of detection with Fru-1,6-P2. Single-turnover experiments with these enzymes in excess over radiolabeled Fru-1,6-P2 were used to measure the rates of Schiff base and product formation. The rate of Schiff base formation was decreased in each of the mutant enzymes, yet the magnitude of this decrease was less than the reduction in the respective kcat. These mutations had a much larger effect, however, on the rate of C3-C4 bond breaking, showing that Lys-146 is crucial at this step of the catalytic cycle.

Animals↗
PubMed1994

Suppression of Gi alpha 2 enhances phospholipase C signalling.

G-proteins mediate transmembrane signalling from a populous group of cell-surface receptors to a smaller group of effectors that includes adenylate cyclase, various ion channels and phospholipase C. Stem cells (F9 teratocarcinoma) or rat osteosarcoma 17/2.8 cells in which Gi alpha 2 expression is abolished by antisense RNA display markedly elevated basal inositol 1,4,5-trisphosphate accumulation and a potentiated phospholipase C response to stimulatory hormones. Expression of the Q205L mutant of Gi alpha 2, which is constitutively active, was found to block persistently hormonally stimulated phospholipase C activity, implicating Gi alpha 2 as an inhibitory regulator of phospholipase C signalling. Analysis using Gi alpha 2-deficient adipocytes of transgenic mice provided further evidence for a role for Gi alpha 2 in phospholipase C regulation, demonstrating in vivo that loss of Gi alpha 2 elevates basal, and markedly potentiates hormonally stimulated, phospholipase C activity. This report demonstrates for the first time that a single G-protein, G12, can regulate two distinct signalling pathways, i.e. adenylate cyclase and phospholipase C.

Adipocytes↗
PubMed1994

Effect of monolayer surface pressure on the activities of phosphoinositide-specific phospholipase C-beta 1, -gamma 1, and -delta 1.

Three isoforms of phospholipase C, either PLC-beta 1, PLC-gamma 1, or PLC-delta 1, were added to the aqueous subphase beneath phospholipid monolayers formed at an air-solution interface, and the initial rate of hydrolysis of phosphatidylinositol 4,5-bisphosphate was measured after addition of 10 microM free Ca2+. The monolayers were formed from mixtures of phosphatidylcholine (65% PC), phosphatidylserine (33% PS), and phosphatidylinositol 4,5-biphosphate (2% PIP2). Increasing the surface pressure of the monolayer, pi, from 15 to 25 mN/m decreases the rate of hydrolysis 16-, 13-, and 5-fold for PLC-beta 1, PLC-gamma 1, and PLC-delta 1, respectively. The simplest interpretation of these results is that a portion of each of the enzymes of area Ap must insert into the monolayer, doing work pi Ap, prior to hydrolysis of PIP2; binding studies with simple model compounds of known cross-sectional area are consistent with this interpretation. Removing the monovalent acidic lipid PS from the monolayer decreases the initial rates of hydrolysis of PIP2 about 3-fold for each PLC isoform, which suggests that negative electrostatic surface potentials increase the PLC activity.

Animals↗
PubMed1994

Enhanced access to rare brain cDNAs by prescreening libraries: 207 new mouse brain ESTs.

To use single-pass cDNA sequencing to characterize low-frequency cDNA clones from a region of the brain that includes the primary site of neurodegeneration in human Parkinson disease, we have developed a prescreening procedure using single brain region first-strand cDNA probes. Selection of cDNA clones giving low hybridization signals allowed the elimination of clones resulting from abundant messages and enrichment for clones corresponding to low-copy messages. Comparative sequencing of standard and prescreened cDNA libraries (191 and 124 clones, respectively) showed that this procedure raised the frequency of novel sequences encountered from 54 to 81%. The increased proportion of novel ESTs justifies the labor of prescreening. Automation of this procedure will accelerate the molecular description of genes expressed in any brain region, or any tissue, and represents a way to maximize access to cDNA sequences for human and mouse genome characterization. In total, the comparative sequencing experiments generated 207 new mouse and 11 new rat brain ESTs.

Animals↗
PubMed1994

Short report: the effect of misoprostol on the anaemia of NSAID enteropathy.

BACKGROUND: Small bowel ulceration is an increasingly recognised complication of therapy with non-steroidal anti-inflammatory drugs (NSAID). The ulceration is a potent site of blood loss contributing to unexplained iron deficiency anaemia in patients with arthritis. No drug is currently available to treat NSAID small bowel ulcers. METHODS: We have retrospectively examined the effect of therapy with the prostaglandin E1 analogue misoprostol on the anaemia of patients with enteroscopically proven NSAID small bowel enteropathy. RESULTS: All of the patients had proven iron deficiency anaemia. Eleven patients received misoprostol and ten received no treatment. Haemoglobin in the misoprostol-treated group rose significantly from median (range) 9.1 (6.2-10.6) g/dL (95% confidence intervals 8.76, 10.13) to 10.6 (6.5-16.8) g/dL (95% confidence intervals 10.06, 11.82); P = 0.004). Those patients who did not receive misoprostol had no significant change in their haemoglobin: 9.1 (7.5-10.6) g/dL to 8.1 (5.6-14.7) g/dL (P = N.S.). CONCLUSION: Misoprostol therapy was associated with an improvement in the anaemia in patients with proven NSAID enteropathy.

Adult↗
PubMed1994

A nose stud retainer clip lost within the nasal cavity discovered on dental radiographs.

It is fairly common for a dental surgeon to come across patients with foreign bodies in the nasal cavity. In this paper we report an unusual case of a nose stud retainer clip being displaced into the nasal cavity by trauma, and its discovery on radiographs taken to assess dental injuries. We also present a review of the literature since 1982, and assess the possible sequelae to nasal foreign bodies.

Adolescent↗
PubMed1994

Intestinal permeability in patients with Crohn's disease and their first-degree relatives.

OBJECTIVE: To measure small intestinal permeability in a group of patients with Crohn's disease in clinical remission and their apparently healthy first-degree relatives. METHODS: Administration of 51Cr-labeled EDTA and subsequent measurement of its excretion in a 24-h urine collection. RESULTS: Excretion of 51Cr-EDTA was not elevated in either the patients or in first-degree relatives. CONCLUSION: Intestinal permeability to 51Cr-EDTA is not raised in patients with Crohn's disease in clinical remission or in their healthy first-degree relatives.

Chromium Radioisotopes↗
PubMed1994

The role of the microbiology laboratory in diagnosing mycobacterial diseases.

Recent surveys show that many mycobacteriology laboratories continue to use less-than-optimal culture and susceptibility methods. This review summarizes available methods to diagnose. Mycobacterium tuberculosis. Although the local epidemiologic characteristics of M tuberculosis will partially determine what diagnostic measures are used, all laboratories should use a broth culture method in addition to a solid medium when culturing for M tuberculosis. Laboratories serving communities where drug resistance is common should use the BACTEC system for susceptibility testing or send isolates to a laboratory that uses it. Conventional testing in this setting must be aggressively discouraged. Rapid genetic amplification methods to detect mycobacteria in clinical specimens can greatly reduce the time needed to diagnose tuberculosis, especially if these methods can reliably detect M tuberculosis in smear-negative specimens. Many other diagnostic methods are being developed and clinicians and laboratories must regularly reassess whether a new method would be beneficial to their patients and the public.

Bacteriological Techniques↗
PubMed1993

Identification of G alpha 11 as the phospholipase C-activating G-protein of turkey erythrocytes.

A 43 kDa phospholipase C-activating protein has been purified previously from turkey erythrocytes and shown to express immunological properties expected of that of the Gq family of G-protein alpha-subunits [Waldo, Boyer, Morris and Harden (1991) J. Biol. Chem. 266, 14217-14225]. Internal amino acid sequence has now been obtained from this protein which shares 50-100% sequence identity with sequences encoded by mammalian G alpha 11 and G alpha q cDNAs. To identify the purified protein unambiguously, it was necessary to compare its amino acid sequence with the sequence encoded by avian G-protein alpha-subunit cDNA. As such, mouse G alpha q was used as a probe to screen turkey brain and fetal-turkey blood cDNA libraries. A full-length cDNA was identified that encodes avian G alpha 11, on the basis of its 96-98% amino acid identity with mammalian G alpha 11. All eight peptides sequenced from the turkey erythrocyte phospholipase C-activating protein are completely contained within the deduced amino acid sequence of the avian G alpha 11 cDNA. Expression of this cDNA in Sf9 cells by using a baculovirus expression system resulted in the production of a 43 kDa protein that reacts strongly with antisera to the Gq family of G-protein alpha-subunits and activated purified avian phospholipase C in an AlF4(-)-dependent manner. Taken together, these results unambiguously identify the protein purified from turkey erythrocytes, on the basis of its capacity to activate avian phospholipase C, as G alpha 11.

Aluminum↗
PubMed1993

Site-directed mutagenesis identifies aspartate 33 as a previously unidentified critical residue in the catalytic mechanism of rabbit aldolase A.

The expression and purification of the rabbit muscle aldolase A (D-fructose 1,6-bisphosphate:D-glyceraldehyde-3-phosphate lyase, EC 4.1.2.13) from an expression plasmid in bacteria is described. The enzyme is produced in bacteria at a level of 300 mg/liter and is indistinguishable from the enzyme isolated from muscle in assays using fructose 1,6-bisphosphate and fructose 1-phosphate. The recombinant enzyme has the same primary, secondary, and quaternary structure as the muscle enzyme. Aspartic acid 33, found near the active site lysine in the crystal structure, is changed to alanine, serine, and glutamic acid by site-directed mutagenesis, resulting in the mutant proteins, D33A, D33S, and D33E, respectively. The mutant enzymes are purified by substrate affinity elution from carboxylmethyl-Sepharose, the same method as that used for the wild-type enzyme. The secondary and quaternary structure of D33A is identical to wild-type aldolase when analyzed by light scattering, gel filtration, and circular dichroism. Moreover, the hexose substrate can be fixed in the active site by reduction of the Schiff base with sodium borohydride, indicating that the active site is not drastically altered. These single mutations in the active site have a serious effect on the activity of the enzyme. In addition, the rate of carbanion oxidation for D33A is 17-29 times slower when the substrate is fructose 1,6-bisphosphate versus dihydroxyacetone phosphate, whereas in the wild-type there is no significant difference in these rates. This evidence and the conservation of this residue in other class I aldolases indicate that aspartic acid 33 is an essential residue in the catalytic mechanism, possibly involved in abstraction of the carbon 4 hydroxyl proton.

Amino Acid Sequence↗
PubMed1993

Artificial intelligence and the supervision of bioprocesses (real-time knowledge-based systems and neural networks).

The ability to supervise and control a highly non-linear and time variant bioprocess is of considerable importance to the biotechnological industries which are continually striving to obtain higher yields and improved uniformity of production. Two AI methodologies aimed at contributing to the overall intelligent monitoring and control of bioprocess operations are discussed. The development and application of a real-time knowledge-based system to provide supervisory control of fed-batch bioprocesses is reviewed. The system performs sensor validation, fault detection and diagnosis and incorporates relevant expertise and experience drawn from both bioprocess engineering and control engineering domains. A complementary approach, that of artificial neural networks is also addressed. The development of neural network modelling tools for use in bioprocess state estimation and inferential control are reviewed. An attractive characteristic of neural networks is that with the appropriate topology any non-linear functional relationship can be modelled, hence significantly reducing model-process mismatch. Results from industrial applications are presented.

Artificial Intelligence↗
PubMed1993

Rejection criteria for endotracheal aspirates from adults.

Although criteria have been established to assess the quality of sputum specimens, no criteria for assessing the quality of endotracheal suction aspirates (ETSA) exist. Therefore, we compared the Gram stain (GS) and culture results for 504 consecutive ETSA specimens. Results recorded for GS included the numbers of squamous epithelial cells (SEC) and polymorphonuclear leukocytes (PML) per low-power field (LPF) (magnification, x100) as well as the quantities and types of organisms per high-power field (HPF) (magnification, x1,000). Culture results were quantitated by organism. Only 15% of ETSA specimens tested by GS contained > 10 SEC per LPF, and 21, 20, and 59% had < or = 10, 11 to 24, and > or = 25 PML per LPF, respectively. For 40% of ETSA specimens, no organisms were visible by GS. Of these specimens, 40% were sterile, 48% grew normal oropharyngeal flora (NF) only, 5% grew 1+ NF (i.e., > 10 colonies in the first quadrant) and 1+ gram-negative rods (GNR), and 7% grew < or = 1+ GNR either alone or in mixed culture. The mean numbers of organisms recovered from ETSA with < or = 10 SEC per LPF and > 10 SEC per LPF were 2.35 and 4.05, respectively. We therefore recommend that ETSA specimens that show no organisms by GS be rejected, in addition to those with > 10 SEC per LPF. Application of these rejection criteria enabled us to reject 847 (41%) of 2,068 ETSA specimens over a 6-month period. This represents a saving of approximately $66,000/year in unnecessary laboratory charges to patients.

Adult↗