Biomedical subjects
Publications and source records attributed to S J Mitchell.
We report four cases of congenital diaphragmatic hernia occurring in two generations of a consanguineous Pakistani family. The affected subjects resembled no recognised genetic syndrome. This family provides further evidence for possible autosomal recessive inheritance of congenital diaphragmatic hernia in some cases.
We have cloned the inorganic pyrophosphatase gene (ppa) from the facultative intracellular pathogen Bartonella bacilliformis and characterized its encoded product. The 531-bp gene is located approximately 1 kb downstream of, and in opposite orientation to, the invasion-associated locus (ialAB) of B. bacilliformis. The predicted protein encoded by ppa is 177 amino acid residues, which is in agreement with in vitro and in vivo synthesis of a protein with an apparent molecular mass of 22-23 kDa. The predicted B. bacilliformis pyrophosphatase (PPase) sequence is 53% identical and 85% similar to the E. coli PPase (EC 3.6.1.1), and contains all 12 of the amino acid residues implicated in the catalytic active site. The isolated B. bacilliformis PPase exhibits an activity of 51 +/- 2 mumol PO4 released/(mg protein.min) at 28 degrees C and pH 8, and is sensitive to inhibition by Ca2+. In keeping with other prokaryotic PPases, B. bacilliformis PPase activity occurs from pH 6 to 10 (optimal pH = 8) and demonstrates high thermostability in the presence of Mg2+ (highest activity at 55 degrees C, relative activity = 80 +/- 3% at pH 8). The cloned B. bacilliformis ppa is able to genetically complement a ppa- mutant strain of E. coli.
We have previously shown significant bubble formation in Medtronic Maxima hard-shell venous reservoirs (HSVRs). In the present study, we not only investigated the mechanism of this bubble formation, but also the extent of bubble clearance by membrane oxygenators and arterial line filters. In addition, we also compared the performance of five HSVRs with respect to bubble formation and venous air filtration. Salvaged clinical CPB circuits containing different HSVRs were studied by downstream Doppler monitoring under fixed flow-decreasing volume, fixed volume-increasing flow, and entrained venous air conditions. Bubbles formed in the Medtronic Maxima top entry HSVR at volumes below 800 ml and flows above 3.5 l min-1, and were incompletely removed by a membrane oxygenator and arterial line filter. Decreased bubbling was seen when the reservoir atmosphere was flushed with CO2, suggesting that these bubbles formed in a fountain at the venous inflow. The Medtronic Maxima Forte HSVR formed significantly fewer bubbles at low volumes, and filtered venous air effectively. Negligible bubble formation occurred in the Sorin, Terumo, or Baxter reservoirs. The minimum recommended operating volume for the Medtronic Maxima top entry reservoir should be reset at 600 ml and this device should always be used with an arterial filter. Bubble formation is substantially reduced in the new Medtronic Maxima Forte HSVR and this device is a good filter for venous air.
Physicians often must decide when an older patient should give up driving. Objective measures of accident risk are lacking, but a simple assessment of function can provide insights. Some medical centers now offer driving evaluation and rehabilitation programs.
BACKGROUND: We report four cases of cutaneous infection with Rhizopus microsporus in vulnerable preterm infants in one neonatal nursery. METHODS: There was no overlap in hospital stay between the first two cases and an extensive programme of environmental sampling was therefore initiated, with special attention being paid to items that had close contact with infants' skin. Samples were cultured by standard techniques, including fungal culture with Sabouraud's medium. Filamentous fungi with non-septate hyphae were presumptively identified as agents of mucormycosis and referred to the Mycology Reference Laboratory, Bristol, UK, for speciation. FINDINGS: The source of infection was identified as wooden tongue depressors, which were used on the nursery to construct splints for intravenous and arterial cannulation sites. The outbreak was ended by the removal of these items from the nursery. INTERPRETATION: Wooden tongue depressors can be a vehicle for transmission of mucormycosis. The combination of warm, humid conditions in neonatal incubators, particularly in association with occlusive dressings, may favour cutaneous fungal invasion and put small, sick babies at risk of infection.
Rat livers were flushed with different preservation solutions and stored at 4 degrees C for 24 h before being reperfused with a synthetic air-equilibrated, water-based solution. Four solutions were tested using this isolated rat liver model: Marshall's hypertonic citrate (HC); modified University of Wisconsin solution (Mod UW); a histidine-based solution (HIS); and a histidine-lactobionate-raffinose-based solution (HLR). After storage, livers were perfused at 4 degrees C for a period of 2 h and biopsy samples taken, at different time points, to investigate energy metabolism. Livers stored in HLR and HIS had higher 24-h storage levels of ATP (0.41 and 0.24 mumol/g respectively; P < 0.05) than those stored in Mod UW and HC. On reperfusion, all groups regenerated ATP by 1-2 h. However, significantly greater levels of ATP regeneration occurred in livers stored in the HLR (1.6 +/- 0.08 mumol/g) and Mod UW (1.3 +/- 0.18) than HC (0.58 +/- 0.19) and HIS (0.96 +/- 0.12); P < 0.05. Energy charge (1) (EC) recovered in all groups but was significantly higher in HLR and Mod UW (0.79 and 0.68, respectively; P < 0.05) than HC and HIS. These represent 95% (HLR) and 80% (Mod UW) of values observed in FIL. During the reperfusion period, total adenine nucleotide levels (TA) did not vary significantly within each storage group, except in the HIS solution. However, TAs were greater with livers stored for 24 h in HLR (2.5 +/- 0.25) and Mod UW (2.7 +/- 0.20) than those the other two storage groups (P < 0.05 in each case). This study has demonstrated that it was possible to resuscitate liver energetics after prolonged hypothermic ischemia by a period of cold reperfusion, and the method can differentiate between preservation solutions. The livers stored in each solution showed varying degrees of success in regeneration of ATP and EC, demonstrating that oxygen was not a limiting factor when using an air-equilibrated perfusate. The solutions providing the better preservation conditions gave the greater resuscitation of liver energetics (Mod UW and HLR). Overall, livers stored in HLR had the greatest resuscitation of energy metabolism, which correlates with survival data from other studies (29-31, 33).
Erythrocyte parasitism, or hemotrophy, is not a common strategy for bacteria. However, Bartonella species are elegantly adapted to parasitize a variety of cell types including red blood cells. Bartonella bacilliformis, a useful model organism for the genus, has been used to study virulence determinants involved in colonization, attachment and invasion of host cells.
Increases in right common carotid artery Doppler ultrasound signals typical of emboli were found in cardiopulmonary bypass patients when the Medtronic Maxima hard-shell adult combined venous and cardiotomy reservoir was operated at reservoir blood volumes near the manufacturer;s recommended minimum of 300 ml. The signals were reduced by increasing the reservoir blood volume. Possible microembolus generation in the top- and bottom-entry versions of this reservoir was investigated using an in vitro circuit and a colour flow Doppler monitor that was interfaced with a microprocessor to count the signals. The reservoir blood volume was progressively lowered in 100 ml increments below 1000 ml, and signals were counted over five minutes at each new level. Signal counts downstream of the reservoir increased exponentially after the volume was decreased below 1000 ml in the bottom-entry version, and 700 ml in the top-entry version. Ultrasonic monitoring, both upstream and downstream of the reservoir, showed that the source of these signals was the reservoir itself, and that recirculation of emboli around the circuit accounted for only a small proportion of the measured increase. Changes in circuit blood prime haematocrit within the range 0.11-0.31 did not alter the signal counts. However, counts were profoundly affected by exposure of the circuit to nitrous oxide via a membrane oxygenator; this showed that the emboli were bubbles. Bubble formation may occur where venous blood enters the reservoir as this results in a fountaining effect when the reservoir volume is low. This effect appears to have been serendipitously reduced, but not eliminated, in the design of the top-entry version. It is recommended that perfusionists should not operate these reservoirs at volumes below 1000 and 700 ml in the bottom- and top-entry versions respectively.
We report the cloning and characterization of the 23S ribosomal RNA (rRNA)-encoding gene (rDNA) of Bartonella bacilliformis (Bb). The 2821-bp gene is preceded by an 11-nucleotide (nt) inverted repeat (IR) located 81 nt upstream in the tRNA(Ala)-23S rDNA intergenic spacer. The gene is followed by an 8-nt IR, five nt downstream in the 23S-5S rDNA intergenic spacer. The nt sequence of the Bb 23S rDNA is most similar to the 23S rDNA of Rhodopseudomonas palustris (Rp), with 85.4% sequence identity. The Bb 23S rDNA has 77.8% identity to the same gene from Escherichia coli (Ec). Secondary structure predictions indicate that the large subunit (LSU) Bb rRNA contains two smaller stem-loops at nt 1459-1544 and 1658-1685, as compared to the corresponding loops from Ec (nt 1405-1597 and 1707-1751, respectively). In addition, the Bb 23S rRNA has a large 72-nt stem-loop at nt 130-201, as compared to the Ec 18-nt stem-loop (nt 131-148). There is no Bb homologue of the 15-nt stem-loop at the 3' end of the Ec molecule (nt 2791-2805). The Bb 23S rRNA lacks the large stem-loop present in the LSU rRNA of closely related Rhodobacter sphaeroides (Rs) (nt position 1225-1331) which is thought to be involved in cleavage of 23S RNA precursor molecules into 16S and 14S rRNA species. This is the first LSU rDNA nt sequence for any member of the Bartonellaceae family.
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Bartonella bacilliformis, the agent of human Oroya fever, invades erythrocytes and causes a severe hemolytic anemia. The ability of two minimally invasive strains of Escherichia coli (DH5 alpha and HB101) to invade human erythrocytes was enhanced 6- to 39-fold by transformation with pIAL1, a plasmid containing a 1,469-bp BamHI fragment from the B. bacilliformis chromosome. Invasiveness was confirmed by gentamicin protection and transmission electron microscopy. DNA hybridization analysis confirmed the presence of the locus in B. bacilliformis KC583 and KC584 and its absence in E. coli chromosomal DNA. Sequencing of the DNA insert of pIAL1 revealed tandem open reading frames of 510 and 558 bp, designated ialA and ialB, respectively. Invasion assays with E. coli containing only an ialA or ialB recombinant suggest that both genes are necessary for invasiveness. The ialA gene is predicted to code for a polypeptide of 170 amino acids (20.1 kDa), and ialB is predicted to code for a polypeptide of 186 amino acids (19.9 kDa). In vitro transcription and translation of pIAL1 produced insert-specific protein bands with masses of approximately 21 and 20 kDa when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Expression of ialA and ialB in E. coli maxicells produced proteins with masses of approximately 21 kDa (IalA) and 18 kDa (IalB). Maxicell and computer analyses suggest that IalB contains an N-terminal secretory signal sequence which is posttranslationally cleaved. Searches of various DNA and protein databases revealed that IalA contains an N-terminal region of 35 amino acids with a high degree of homology to an NTPase consensus domain. There is 63.6% sequence conservation between the IalB protein and the invasion-associated protein Ail of Yersinia enterocolitica.
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BACKGROUND: It is known that soluble fiber in the diet can lower blood lipid levels. It is less certain, however, that eating foods with soluble fiber will further lower blood lipids when the intake of saturated fat and cholesterol has already been reduced to very low levels. Furthermore, the mechanism of the lipid-lowering effect of fiber has not been elucidated. METHODS: To address these questions, we studied 43 volunteers with hyperlipidemia in a crossover study involving two four-month dietary periods. The two metabolic diets contained foods high in either soluble or insoluble fiber and were separated by a two-month National Cholesterol Education Program Step 2 diet. The metabolic diets were low in saturated fat (< 4 percent of total calories) and cholesterol (< 25 mg per 1000 kcal), high in carbohydrate (> or = 60 percent of total calories), and very high in fiber (> 24 g per 1000 kcal). RESULTS: Blood lipids fell to their lowest levels by week 4 of both study diets. When the soluble-fiber period was compared with the insoluble-fiber period, the subjects' total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol levels were found to be lower by a mean (+/- SE) of 4.9 +/- 0.9 percent (P < 0.001), 4.8 +/- 1.3 percent (P < 0.001), and 3.4 +/- 1.3 percent (P = 0.014), respectively. In contrast, the ratio of total to HDL cholesterol was not significantly different during the two dietary periods. The loss of fecal bile acids was 83 +/- 14 percent greater during the soluble-fiber period than during the insoluble-fiber period (P < 0.001) and was related to the differences in total and LDL cholesterol and apolipoprotein B levels (r = 0.42, P = 0.005; r = 0.49, P < 0.001; and r = 0.33, P = 0.035, respectively). The difference in serum cholesterol levels between the two dietary periods was greater among the men (7.5 +/- 1.2 percent, P < 0.001) than among the women (3.4 +/- 1.2 percent, P = 0.008). CONCLUSIONS: Very high intakes of foods rich in soluble fiber lower blood cholesterol levels even when the main dietary modifiers of blood lipids--namely, saturated fat and cholesterol--are greatly reduced.
This study describes the organization and topography of the descending efferent projections from the monkey ventral pallidum. The main efferent projections from the globus pallidus are to the subthalamus, to the thalamus, and to the substantia nigra. Although these projections have been well established for the dorsal pallidum, the projections of the ventral pallidum have not been explored in primates. The results of this study add an important link in how information from the limbic lobe is channeled through the basal ganglia in monkeys. Anterograde tracers, Phaseolus vulgaris-leucoagglutinin, and tritiated amino acids were injected into various regions of the ventral pallidum. The descending efferent projection from the ventral pallidum in monkeys terminates primarily in the subthalamic nucleus and adjacent lateral hypothalamus, in the substantia nigra, and in the lateral habenular nucleus. Although terminals are also found in the thalamus, these are relatively sparse. The projections to the subthalamic nucleus and the lateral hypothalamus are topographically arranged, while those to the substantia nigra are not. These results suggest that pathways from distinct pallidal regions that receive specific striatal input terminate in distinct regions of the subthalamic/hypothalamic regions, thus maintaining a topographic arrangement. Projections to the substantia nigra, however, overlap extensively, suggesting convergence of terminals from different ventral pallidal regions. The relatively small projection to the thalamus raises the question that without a prominent thalamic projection, is this system parallel to that described for the dorsal globus pallidus?
To evaluate the clinical efficacy of interferon-alpha in hepatocellular carcinoma, 71 adult Chinese patients with histologically proven inoperable hepatocellular carcinoma were randomized to receive recombinant interferon-alpha 2a (50 x 10(6) IU/m2) intramuscularly three times a week (n = 35) or no antitumor therapy (n = 36). The survival of interferon-alpha-treated patients was significantly better than that of patients who received no antitumor therapy (p = 0.0471); median lengths of survival were 14.5 and 7.5 wk, respectively. Objective tumor regression greater than 50% was observed in 31.4% (11 of 35) of patients receiving interferon-alpha. Interferon-alpha induced tumor regression greater than 50% in 11 (31.4%) patients. Compared with the group receiving no antitumor therapy, the interferon-alpha therapy group had more tumor regression (p < 0.0001) and less tumor progression (p = 0.001). This high-dose interferon-alpha therapy was relatively well tolerated; only 34.3% of patients required reduction of dosage by one third or one half because of persistent fatigue. Two patients with diabetes mellitus (one also had tabes dorsalis) exhibited mental deterioration that might have been partially attributable to interferon-alpha therapy. We conclude that interferon-alpha is useful in a proportion of Chinese patients with inoperable hepatocellular carcinoma, both in prolonging survival and in inducing tumor regression.
We have estimated DNA sequence variation within and between two populations of Drosophila ananassae, using six-cutter restriction site variation at vermilion (v) and furrowed (fw). These two gene regions are located close to the centromere on the left and right X chromosome arms, respectively. In the fw region, no DNA polymorphism was detected within each population. In the v region, average heterozygosity per nucleotide was very low in both populations (pi = 0.0005 in the Burma population, and 0.0009 in the India population). These estimates are significantly lower than those from loci in more distal gene regions. The distribution of DNA polymorphisms between both populations was also striking. At fw, three fixed differences between the Burma and India populations were detected (two restriction site differences and one insertion/deletion of approximately 2 kb). At v, each DNA polymorphism in high frequency in the total sample was nearly fixed in one or the other population, although none of them reached complete fixation. The observed pattern of reduced variation within populations and fixed differences between populations appears to correlate with recombination rate. We conclude that recent hitchhiking associated with directional selection is the best explanation for this pattern. The data indicate that different selective sweeps have occurred in the two populations. The possible role of genetic hitchhiking in rapid population differentiation in gene regions of restricted recombination is discussed.
To assess the contributions of the basal forebrain cholinergic nuclei to visual recognition memory in macaques, we compared the effects of lesions of (a) the nucleus basalis of Meynert, (b) the medial septal and diagonal band nuclei, and (c) all nuclei combined on performance of delayed nonmatching-to-sample with trial-unique stimuli. Whereas monkeys with the separate lesions did not differ from each other or from normal control animals, those with combined lesions showed a significant impairment. With time and extended practice, however, the performance of the animals with combined lesions recovered to normal levels. During the recovery period, these monkeys showed an initially increased sensitivity to scopolamine that later dissipated, at which time they also failed to show the improvement that follows physostigmine administration in normal animals. Postmortem assessment of cortical choline acetyltransferase activity revealed that only the group with combined lesions had significant depletion of this enzyme. The results suggest that (1) the basal forebrain cholinergic system participates in mnemonic processes in primates and that (2) extensive damage to this system is necessary before impairments in recognition memory, even transient ones, can be observed.
A food and nutrition questionnaire was administered to students in a college basic nutrition course (basic nutrition students) and to others in unrelated general studies classes (control students) at the beginning and end of the semester to determine changes other than in academic knowledge of nutrition. Analysis with chi square (p less than .05) compared pre-semester responses (no. = 279) and post-semester responses (no. = 218) with those of 24 senior dietetics students (dietetics majors). After completing the course, all basic nutrition students responded that they had learned a lot about nutrition, and 45% indicated that they had made dietary changes because of this learning. Changes included increased confidence in the adequacy of their diets, decreased supplement use, and reduced fat content of milk usually consumed. Some misunderstandings of carbohydrates in foods were not improved. The similarity of responses by basic nutrition and control students to the pre-semester questionnaire suggests that enrollees in a basic nutrition class may be representative of the general student body in needs for nutrition education. The basic class for non-nutrition majors can effect changes in dietary practices; their nutrition education needs may be used to plan nutrition education of the general student population.