Biomedical subjects
J G Morris
Publications and source records attributed to J G Morris.
Identification of a group 1-like capsular polysaccharide operon for Vibrio vulnificus.
Virulence of Vibrio vulnificus correlates with changes in colony morphology that are indicative of a reversible phase variation for expression of capsular polysaccharide (CPS). Encapsulated variants are virulent with opaque colonies, whereas phase variants with reduced CPS expression are attenuated and are translucent. Using TnphoA mutagenesis, we identified a V. vulnificus CPS locus, which included an upstream ops element, a wza gene (wza(Vv)), and several open reading frames with homology to CPS biosynthetic genes. This genetic organization is characteristic of group 1 CPS operons. The wza gene product is required for transport of CPS to the cell surface in Escherichia coli. Polar transposon mutations in wza(Vv) eliminated expression of downstream biosynthetic genes, confirming operon structure. On the other hand, nonpolar inactivation of wza(Vv) was specific for CPS transport, did not alter CPS biosynthesis, and could be complemented in trans. Southern analysis of CPS phase variants revealed deletions or rearrangements at this locus. A survey of environmental isolates indicated a correlation between deletions in wza(Vv) and loss of virulent phenotype, suggesting a genetic mechanism for CPS phase variation. Full virulence in mice required surface expression of CPS and supported the essential role of capsule in the pathogenesis of V. vulnificus.
Cohort studies of health effects among people exposed to estuarine waters: North Carolina, Virginia, and Maryland.
A variety of human symptoms have been associated with exposure to the dinoflagellate Pfiesteria and have been grouped together into a syndrome termed "possible estuary-associated syndrome." Prospective cohort studies of health effects associated with exposure to estuarine waters that may contain Pfiesteria spp. and related organisms are in progress in North Carolina, Virginia, and Maryland. The three studies recruited cohorts of 118-238 subjects who work or engaged in recreation in estuary waters. Baseline health and neuropsychological evaluations are conducted, and study subjects are followed prospectively for 2-5 years with periodic assessments of health and performance on a battery of neuropsychological tests. Health symptoms and estuary water exposure are recorded by telephone interviews or diaries every 1-2 weeks. Water quality information, including measurements of Pfiesteria spp., is collected in the areas where the subjects are working. Because it is not possible to measure individual exposure to Pfiesteria or a toxin produced by this organism, these studies examine surrogate exposure measures (e.g., time spent in estuary waters, in a fish kill area, or in waters where Pfiesteria DNA was detected by molecular amplification). Preliminary analyses of the first 2 years (1998-2000) of data indicate that none of the three ongoing cohorts have detected adverse health effects. However, there have not been any reported fish kills associated with Pfiesteria since the studies began, so it is possible that none of the study subjects have been exposed to toxin-producing Pfiesteria spp.
Human health effects and Pfiesteria exposure: a synthesis of available clinical data.
An association between human illness and exposure to Pfiesteria was first observed among laboratory personnel working with the microorganism. In 1997, in the setting of Pfiesteria activity on the Pocomoke River in Maryland, difficulties with learning and memory were epidemiologically associated with high-level exposure to waterways in which the organism was known to be present. In the Maryland studies, neurocognitive function of affected persons returned to within normal ranges within a period of 3-6 months. Persons with the most severe neurocognitive deficits were significantly more likely to have skin lesions characterized on biopsy by evidence of a toxic/allergic inflammatory reaction. Acute high-level exposures to waterways where Pfiesteria has been identified have been linked with eye and respiratory irritation, headache, and gastrointestinal complaints. Recent data, collected using molecular techniques, suggest that the organism is present in multiple locations in the Chesapeake Bay environment; available data are insufficient to comment on the possible cumulative health impact of chronic low-level environmental exposure to Pfiesteria.
Chronic ingestion of high concentrations of cholecalciferol in cats.
OBJECTIVE: To determine whether ingestion of 63 times the recommended amount of vitamin D3 (cholecalciferol) results in renal calcification or damage in cats. ANIMALS: 20 four-month-old kittens, 17 queens, and 20 kittens born to these queens. PROCEDURE: 4-month-old kittens and queens were given a purified diet with 846 microg of cholecalciferol/kg of diet (high vitamin D3 diet) or 118 microg of cholecalciferol/kg of diet (control diet) for 18 months. Kittens born to queens were weaned onto the same diet given to dams. RESULTS: There were no apparent adverse effects of the high vitamin D3 diet. Plasma cholecalciferol and 25-hydroxycholecalciferol (25-OHD3) concentrations of queens and 4-month-old kittens given the high vitamin D3 diet significantly increased with time. At 6 months, plasma cholecalciferol concentrations in these kittens and queens were 140.0+/-7.3 nmol/L and 423.6+/-26.6 nmol/L, respectively (10 times initial values). Corresponding 25-OHD3 concentration in queens was 587.5+/-59.4 nmol/L (2.5-fold increase over initial values). At 3 months of age, kittens born to queens given the high vitamin D3 diet had an increase in serum BUN and calcium concentrations and a decrease in RBC and serum total protein, albumin, and hemoglobin concentrations. By 18 months, these kittens had an increase in plasma cholecalciferol (276.0+/-22.2 nmol/L) and 25-OHD3 (1,071.9+/-115.3 nmol/L) concentrations. However, all indices of renal function and the appearance of renal tissue on histologic evaluation were normal. CONCLUSIONS AND CLINICAL RELEVANCE: These results indicate that cats are resistant to cholecalciferol toxicosis when the diet is otherwise complete and balanced.
Bacteriophages as therapeutic agents.
The emergence of antibiotic resistance among pathogenic bacteria is one of the most critical problems of modern medicine, and novel, effective approaches for treating infections caused by multidrug-resistant bacteria are urgently required. In this context, one intriguing approach is to use bacteriophages (viruses that kill bacteria) to eliminate specific bacterial pathogens. Bacteriophage therapy was widely used around the world in the 1930s and 1940s, and it is still used in Eastern Europe and the former Soviet Union. However, phage therapy was all but abandoned in the West after antibiotics became widely available. Promising results from recent animal studies using phages to treat bacterial infections, together with the urgent need for novel and effective antimicrobials, should prompt additional rigorous studies to determine the value of this therapeutic approach.
Objective quantification of resting and activated parkinsonian rigidity: a comparison of angular impulse and work scores.
The clinical assessment of rigidity is influenced by a number of variables which limit the reproducibility of rating scores and the usefulness of comparisons between subjects. We evaluated an objective measure of rigidity which uses unpredictable but reproducible limb perturbations mimicking the waveform, rate, and amplitude of those used in the clinical examination; and evaluates total resistive force, thus avoiding assumptions about the relative influence of elastic, viscous, or inertial components of the measured resistive forces on the genesis of rigidity. We then used this measure to quantify the effects of an activation procedure on parkinsonian rigidity, because this forms an important but poorly understood part of the routine clinical examination. We studied 20 patients with a clinical diagnosis of Parkinson's disease and 10 age-matched control subjects. A torque motor was used to deliver reproducible, transient, sinusoidal perturbations varying between 1.0 and 1.5 Hz. To quantify rigidity, we calculated angular impulse scores, which reflect the relationship between change in total resistive torque and time. Angular impulse scores were compared with work scores, which have previously been found to correlate with clinical assessments of rigidity. All subjects were studied at rest and with activation. Angular impulse scores were more consistently correlated with rigidity and more clearly differentiated between patients and control subjects than work scores. Activation increased both clinical and objective rigidity scores; activated angular impulse scores ranged from approximately 100%-200% of resting values. When plotted against clinical rigidity scores, activated angular impulse scores lay on a continuum with resting values. We conclude that angular impulse is a valid objective measure of parkinsonian rigidity. Activation increases rigidity, but to varying degrees in different patients. To improve the sensitivity and reproducibility of clinical rigidity assessments, parkinsonian rating scales should include separate resting and activated scores.
Progressive myoclonic ataxia associated with celiac disease presenting as unilateral cortical tremor and dystonia.
Explore the source record for details and available documents.
Pfiesteria: harmful algal blooms as indicators of human: ecosystem interactions.
Explore the source record for details and available documents.
Physiological and metabolic responses of female games and endurance athletes to prolonged, intermittent, high-intensity running at 30 degrees and 16 degrees C ambient temperatures.
Eight female games players (GP) and eight female endurance athletes (EA) ran intermittently at high-intensity and for prolonged periods in hot (30 degrees C) and moderate (16 degrees C) ambient temperatures. The subjects performed a two-part (A, B) test based on repeated 20-m shuttle runs. Part A comprised 60 m of walking, a maximal 15-m sprint, 60 m of cruising (90% maximal oxygen uptake, VO(2max)) and 60 m of jogging (45% VO(2max)) repeated for 75 min with a 3-min rest every 15 min. Part B involved an exercise and rest pattern of 60-s running at 100% VO(2max) and 60-s rest which was continued until fatigue. Although the GP and EA did not respond differently in terms of distances completed, performance was 25 (SEM 4)% less (main effect trial, P < 0.01) in the hot (HT) compared with the moderate trial (MT). Sprints of 15 m took longer to complete in the heat (main effect, trial, P < 0.01), and sprint performance declined during HT but not MT (interaction, trial x time, P < 0.01). A very high correlation was found between the rate of rise in rectal temperature in HT and the distance completed [GP, r =-0.94, P < 0. 01; EA (n = 7), r = -0.93, P < 0.01]. Blood lactate [La(-) ](b) and plasma ammonia [NH(3)](p1) concentrations were higher for GP than EA, but were similar in HT and MT [La(-) ](b), HT: GP vs EA, 8.0 (SEM 0. 9) vs 4.9 (SEM 1.1) mmol x l(-1); MT: GP vs EA, 8.0 (SEM 1.3) vs 4.4 (SEM 1.2) mmol x l(-1); interaction, group x time, P < 0.01; [NH(3)](p1), HT: GP vs EA, 70.1 (SEM 12.7) vs 43.2 (SEM 6.1) mmol x l(-1); MT: GP vs EA, 76.8 (SEM 8.8) vs 32.5 (SEM 3.8) micromol x l(-1); interaction, group x time, P < 0.01. Ad libitum water consumption was higher in HT [HT: GP vs EA, 18.9 (SEM 2.9) vs 13.5 (SEM 1.7) ml x kg(-1) x h(-1); MT: GP vs EA, 12.7 (SEM 3.7) vs 8.5 (SEM 1.5) ml x kg(-1) x h(-1); main effect, group, n.s.; main effect, trial, P < 0.01]. These results would suggest that elevated body temperature is probably the key factor limiting performance of prolonged, intermittent, high-intensity running when the ambient temperature is high, but not because of its effect on the metabolic responses to exercise.
Spo0A directly controls the switch from acid to solvent production in solvent-forming clostridia.
The spo0A genes of Clostridium beijerinckii NCIMB 8052 and Clostridium cellulolyticum ATCC 35319 were isolated and characterized. The C-terminal DNA-binding domains of the predicted products of spo0A from these two organisms, as well as 16 other taxonomically diverse species of Bacillus and Clostridium, show extensive amino acid sequence conservation (56% identity, 65% similarity over 104 residues). A 12-amino-acid motif (SRVERAIRHAIE) that forms the putative DNA recognition helix is particularly highly conserved, suggesting a common DNA target. Insertional inactivation of spo0A in C. beijerinckii blocked the formation of solvents (as well as spores and granulose). Sequences resembling Spo0A-binding motifs (TGNCGAA) are found in the promoter regions of several of the genes whose expression is modulated at the onset of solventogenesis in Clostridium acetobutylicum and C. beijerinckii. These include the upregulated adc gene, encoding acetoacetate decarboxylase (EC 4.1.1. 4), and the downregulated ptb gene, encoding phosphotransbutyrylase (EC 2.3.1.c). In vitro gel retardation experiments using C. acetobutylicum adc and C. beijerinckii ptb promoter fragments and recombinant Bacillus subtilis and C. beijerinckii Spo0A suggested that adc and ptb are directly controlled by Spo0A. The binding affinity was reduced when the 0A boxes were destroyed, and enhanced when they were modified to conform precisely to the consensus sequence. In vivo analysis of wild-type and mutagenized promoters transcriptionally fused to the gusA reporter gene in C. beijerinckii validated this hypothesis. Post-exponential phase expression from the mutagenized adc promoter was substantially reduced, whereas expression from the mutagenized ptb promoter was not shut down at the end of exponential growth.
Treatment of Parkinson's disease.
The aim of current treatment of Parkinson's disease is to ameliorate the symptoms while seeking to lessen the potential development of late levodopa complications. To this end, there is ample evidence that the early use of dopamine agonists is beneficial in younger Parkinsonian patients but monotherapy with dopamine agonists is for only a select few. Nonergot dopamine agonists offer the potential for fewer side effects. Lower dose levodopa therapy delays the onset and reduces severity of dyskinesia and end of dose failure. However levodopa remains the treatment of choice in Parkinson's disease and should not be restricted unnecessarily in patients with disability. There is no evidence that levodopa is toxic to dopaminergic neurons in people with Parkinson's disease. As yet, no drugs are of proven neuroprotective value. Dopamine agonists, catechol-o-methyltransferase inhibitors, amantadine and apomorphine have differing but beneficial roles in the management of levodopa side effects. Ablative surgery and deep brain stimulation of thalamus, globus pallidus and subthalamic nucleus are increasingly available but choice of procedure depends not just on patient symptomatology, but also on local experience and results. Ideally, deep brain stimulation is the treatment of choice as it offers less morbidity than bilateral ablative surgery, the possibility of postoperative adjustments and the potential for reversibility if better treatments become available.
A role for the substantia nigra pars reticulata in the gaze palsy of progressive supranuclear palsy.
We examined the topography and degree of cell loss within basal ganglia structures commonly involved in progressive supranuclear palsy in order to identify any relationship between degeneration in these nuclei and gaze palsy. Serial section analyses and unbiased quantitative techniques were applied to brain tissue from six cases with progressive supranuclear palsy (four with gaze palsy and two without) and six controls with no neurological or neuropathological abnormalities. The total number of nucleolated neurons within the substantia nigra pars compacta (SNc) and reticulata (SNr), the subthalamic nucleus, and the internal and external segments of the globus pallidus was determined for all subjects and the data expressed as percentages of control values to compare degeneration across these basal ganglia structures. The density of neurofibrillary tangles was also evaluated within these structures. Despite significant subcortical neurofibrillary tangle formation in all cases, there was considerable variability in the degree of neuronal cell loss in all basal ganglia regions, except the SNc which was consistently affected. There was no correlation between the ranked density of neurofibrillary tangles and the degree of neuronal cell loss in any basal ganglia region. Comparisons between cases with and without gaze palsy revealed a 40% greater decrease in the number of SNr neurons in cases with gaze palsy (75 +/- 8% loss) compared with those without (35 +/- 14% loss). This was the largest difference between these cases. As the SNr projects to the superior colliculus, degeneration of this basal ganglia structure may disrupt eye movements in progressive supranuclear palsy.
Progressive supranuclear palsy pathology caused by a novel silent mutation in exon 10 of the tau gene: expansion of the disease phenotype caused by tau gene mutations.
Genetic mutations in the tau gene on chromosome 17 are known to cause frontotemporal dementias. We have identified a novel silent mutation (S305S) in the tau gene in a subject without significant atrophy or cellular degeneration of the frontal and temporal cortices. Rather the cellular pathology was characteristic of progressive supranuclear palsy, with neurofibrillary tangles concentrating within the subcortical regions of the basal ganglia. Two affected family members presented with symptoms of dementia and later developed neurological deficits including abnormality of vertical gaze and extrapyramidal signs. The third presented with dystonia of the left arm and dysarthria, and later developed a supranuclear gaze palsy and falls. The mutation is located in exon 10 of the tau gene and forms part of a stem-loop structure at the 5' splice donor site. Although the mutation does not give rise to an amino acid change in the tau protein, functional exon-trapping experiments show that it results in a significant 4.8-fold increase in the splicing of exon 10, resulting in the presence of tau containing four microtubule-binding repeats. This study provides direct molecular evidence for a functional mutation that causes progressive supranuclear palsy pathology and demonstrates that mutations in the tau gene are pleiotropic.
Dietary copper influences reproduction in cats.
The objective of this study was to determine the copper requirement of female cats (queens) for gestation. Cuproenzyme activities were evaluated to identify a noninvasive indicator of copper status. This study used a depletion-repletion model. Specific pathogen-free queens (n = 28) were adapted to a purified diet; after consuming a copper-depletion diet (0.8 mg Cu/kg diet) for 4 mo, they were randomly allocated to three dietary treatment groups receiving copper sulfate at 4.0, 5.8 or 10.8 mg Cu/kg diet. Four queens underwent liver biopsies at two time points during the study. Plasma samples were analyzed for copper concentrations, extracellular superoxide dismutase, ceruloplasmin and diamine oxidase activities. Only liver copper concentrations were responsive to dietary copper intake. The dietary concentration of copper had a significant effect on the time taken for queens to conceive (P = 0.04). There was a negative linear relationship between dietary copper (x = Cu mg/kg diet) and the mean time (y = days) for queens to conceive (y = 43.38-2.87x; R(2) = 0.97). The current NRC recommendation of 5 mg/kg diet copper for cats appears marginal for optimal reproduction.
Sequence analysis of TnphoA insertion sites in Vibrio cholerae mutants defective in rugose polysaccharide production.
Vibrio cholerae can switch from a smooth to a wrinkled or rugose colony phenotype characterized by the secretion of a polysaccharide that enables the bacteria to survive harsh environmental conditions. In order to understand the genetic basis of rugosity, we isolated TnphoA-induced stable, smooth mutants of two O1 El Tor rugose strains and mapped the insertion sites in several of the mutants using a modified Y-adapter PCR technique. One of the TnphoA insertions was mapped to the first gene of the vps region that was previously shown to encode the rugose polysaccharide biosynthesis cluster. Three insertions were mapped to a previously unknown hlyA-like gene, also in the vps region. Five other insertions were found in loci unlinked to the vps region: (i) in the epsD gene (encodes the "secretin" of the extracellular protein secretion apparatus), (ii) in a hydG-like gene (encodes a sigma(54)-dependent transcriptional activator similar to HydG involved in labile hydrogenase production in Escherichia coli, (iii) in a gene encoding malic acid transport protein upstream of a gene similar to yeiE of E. coli (encodes a protein with similarities to LysR-type transcriptional activators), (iv) in dxr (encodes 1-deoxy-D-xylulose 5-phosphate reductoisomerase), and (v) in the intergenic region of lpd and odp (encode enzymes involved in the pyruvate dehydrogenase complex formation). These data suggest the involvement of a complex regulatory network in rugose polysaccharide production and highlight the general utility of the Y-adapter PCR technique described here for rapid mapping of transposon insertion sites.
Phylogeny of Vibrio cholerae based on recA sequence.
We sequenced a 705-bp fragment of the recA gene from 113 Vibrio cholerae strains and closely related species. One hundred eighty-seven nucleotides were phylogenetically informative, 55 were phylogenetically uninformative, and 463 were invariant. Not unexpectedly, Vibrio parahaemolyticus and Vibrio vulnificus strains formed out-groups; we also identified isolates which resembled V. cholerae biochemically but which did not cluster with V. cholerae. In many instances, V. cholerae serogroup designations did not correlate with phylogeny, as reflected by recA sequence divergence. This observation is consistent with the idea that there is horizontal transfer of O-antigen biosynthesis genes among V. cholerae strains.
Mutations in the extracellular protein secretion pathway genes (eps) interfere with rugose polysaccharide production in and motility of Vibrio cholerae.
Vibrio cholerae is the causal organism of the diarrheal disease cholera. The rugose variant of V. cholerae is associated with the secretion of an exopolysaccharide. The rugose polysaccharide has been shown to confer increased resistance to a variety of agents, such as chlorine, bioacids, and oxidative and osmotic stresses. It also promotes biofilm formation, thereby increasing the survival of the bacteria in the aquatic environments. Here we show that the extracellular protein secretion system (gene designated eps) is involved directly or indirectly in the production of rugose polysaccharide. A TnphoA insertion in epsD gene of the eps operon abolished the production of rugose polysaccharide, reduced the secretion of cholera toxin and hemolysin, and resulted in a nonmotile phenotype. We have constructed defined mutations of the epsD and epsE genes that affected these phenotypes and complemented these defects by plasmid clones of the respective wild-type genes. These results suggest a major role for the eps system in pathogenesis and environmental survival of V. cholerae.