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Biomedical subjects

J G Morris

Publications and source records attributed to J G Morris.

At least 73 records · Page 4Linked to original sources
PubMed1999

Diphtheria in the Republic of Georgia: use of molecular typing techniques for characterization of Corynebacterium diphtheriae strains.

Sixty-six Corynebacterium diphtheriae strains (62 of the gravis biotype and 4 of the mitis biotype) isolated during the Georgian diphtheria epidemic of 1993 to 1998 and 13 non-Georgian C. diphtheriae strains (10 Russian and 3 reference isolates) were characterized by (i) biotyping, (ii) toxigenicity testing with the Elek assay and PCR, (iii) the randomly amplified polymorphic DNA (RAPD) technique, and (iv) pulsed-field gel electrophoresis (PFGE). Fifteen selected strains were ribotyped. Six RAPD types and 15 PFGE patterns were identified among all strains examined, and 12 ribotypes were found among the 15 strains that were ribotyped. The Georgian epidemic apparently was caused by one major clonal group of C. diphtheriae (PFGE type A, ribotype R1), which was identical to the predominant epidemic strain(s) isolated during the concurrent diphtheria epidemic in Russia. A dendrogram based on the PFGE patterns revealed profound differences between the minor (nonpredominant) epidemic strains found in Georgia and Russia. The methodologies for RAPD typing, ribotyping, and PFGE typing of C. diphtheriae strains were improved to enable rapid and convenient molecular typing of the strains. The RAPD technique was adequate for biotype differentiation; however, PFGE and ribotyping were better (and equal to each other) at discriminating between epidemiologically related and unrelated isolates.

Bacterial Typing Techniques↗
PubMed1999

The sydney multicentre study of Parkinson's disease: progression and mortality at 10 years.

OBJECTIVES: To report on a 10 year follow up of patients with idiopathic Parkinson's disease, particularly with respect to mortality and the effect of early treatment with bromocriptine. METHODS: The patients are from the 149 new patients recruited for a double blind, randomised study of low dose levodopa-carbidopa versus low dose bromocriptine. Patients were examined neurologically at least yearly. Neuropsychological examinations were performed at 0, 3, 5, and 10 years. Mortality and cause of death in these patients were compared with the Australian population using standardised mortality ratios (SMRs). Mortality and disease progression were compared by sex and treatment group. Predictors of death within 10 years, nursing home admission, and progression in Columbia score of >/=20 points were examined by logistic regression analysis. RESULTS: Thirteen patients were excluded as having atypical Parkinsonism and six were lost to follow up. All available patients have been followed up for 10 years. Fifty patients (38%) were dead by 10 years and 63 by the last follow up. The SMR was 1.58 for all patients (p<0. 001). There was no significant difference in SMRs between the sexes. The mean duration of disease until death was 9.1 years. Parkinson's disease was thought to have contributed substantially to the death of 30 patients. The most common cause of death was pneumonia. Women progressed at a similar rate to men until 8 years, when the severity of their disease as measured by Hoehn and Yahr stage became greater (p<0.05). Older age of onset correlated with increased risk of death but the SMR was increased even in those aged <70 years (SMR 1.80, p=0.03). Early use of bromocriptine did not reduce mortality or slow progression of disease. One quarter of all patients had been admitted to nursing homes by 10 years. Only four patients were still employed. CONCLUSIONS: Mortality in Parkinson's disease remains increased despite low dose levodopa-carbidopa therapy and no additional benefit was gained from early use of bromocriptine. Duration of disease was similar to that in the era before levodopa.

Age Distribution↗
PubMed1999

Decreased seroprevalence for Toxoplasma gondii in Seventh Day Adventists in Maryland.

Despite its widespread prevalence, uncertainties remain about the relative contribution of various routes of transmission to the overall rate of infection with Toxoplasma gondii, particularly in developed countries. To explore the hypothesis that meat consumption is an important risk factor for infection, a cross-sectional seroprevalence study was performed on healthy adults in one region in the state of Maryland. The population included Seventh Day Adventists who as a group follow a diet containing no meat, and control community volunteers who were not Seventh Day Adventists. Thirty-one percent of the population had serologic evidence of T. gondii infection. People with T. gondii infection were older (49 versus 42 years old; P < 0.01, by t-test) and less likely to be Seventh Day Adventists (24% versus 50%; P < 0.01, by chi-square test) than people without T. gondii infection. When adjustments were made for age and gender through multiple logistic regression, Seventh Day Adventists had a significantly decreased risk of T. gondii infection (odds ratio = 0.21, 95% confidence interval = 0.09-0.46, P = 0.0001) compared with the controls. While the basis for this effect remains to be determined, one possible protective factor is the general adherence of Seventh Day Adventists to a diet that does not contain meat.

Adult↗
PubMed1999

Dynamics of SCR, EEG, and ERP activity in an oddball paradigm with short interstimulus intervals.

Studies of concurrent central, and autonomic activity using a conventional event-related potential (ERP) oddball paradigms, are considered useful in elucidating the relationship between central and autonomic responses, but the autonomic response tends to overlap. A new method was used to decompose and score overlapping skin conductance responses (SCR). This method enabled examination of dynamic relationships of phasic SCR, prestimulus electroencephalogram (EEG), and ERP to auditory target stimuli in 50 normal adults. SCR amplitude was negatively correlated to EEG and N200 amplitude. The SCR amplitude changes over time exhibited an exponential decline opposite to those of N200, alpha, and beta. All the fitted exponential functions had a time constant of 1-2 min. The findings suggest that a N200 component, active in the auditory sensory discrimination, is concomitant with the SCR. The narrow range of the time constant may provide a clue to the conjoint processes underlying central and autonomic adaptive functions.

Adult↗
PubMed1998

Detection of MELAS A3243G point mutation in muscle, blood and hair follicles.

Polymerase chain reaction (PCR) based methods for the diagnosis and screening of the mitochondrial disorders have been well established. A number of tissues are routinely used. In this study, we compared the detection rate for MELAS A3243G point mutation in muscle, blood and hair follicles. Ten subjects were studied; mean age was 47 years, (SD 16, range 23-73). All ten subjects had the MELAS A3243G point mutation detected in muscle and hair follicles, but only five had the abnormality in blood samples. The rate of detection of the point mutation in blood samples was age dependent. MtDNA analysis on hair follicles is as sensitive as muscle in detecting this mutation. Analysis using blood samples is not as sensitive, particularly in older subjects. The absence of the mutation in blood samples suggests that there is a preferential selection process for normal (wild type) mtDNA over time. This may be related to the rate of cell division and energy requirements of each tissue.

Adult↗
PubMed1998

Learning and memory difficulties after environmental exposure to waterways containing toxin-producing Pfiesteria or Pfiesteria-like dinoflagellates.

BACKGROUND: At the beginning of autumn, 1996, fish with "punched-out" skin lesions and erratic behaviour associated with exposure to toxins produced by Pfiesteria piscicida or Pfiesteria-like dinoflagellate species were seen in the Pocomoke River and adjacent waterways on the eastern shore of the Chesapeake Bay in Maryland, USA. In August, 1997, fish kills associated with Pfiesteria occurred in these same areas. People who had had contact with affected waterways reported symptoms, including memory difficulties, which raises questions about the human-health impact of environmental exposure to Pfiesteria toxins. METHODS: We assessed 24 people who had been exposed. We collected data on exposure history and symptoms, did a complete medical and laboratory assessment (13 people), and carried out a neuropsychological screening battery. Performance on neuropsychological measures was compared with a matched control group. RESULTS: People with high exposure were significantly more likely than occupationally matched controls to complain of neuropsychological symptoms (including new or increased forgetfulness); headache; and skin lesions or a burning sensation of skin on contact with water. No consistent physical or laboratory abnormalities were found. However, exposed people had significantly reduced scores on the Rey Auditory Verbal Learning and Stroop Color-Word tests (indicative of difficulties with learning and higher cognitive function), and the Grooved Pegboard task. There was a dose-response effect with the lowest scores among people with the highest exposure. By 3-6 months after cessation of exposure, all those assessed had test scores that had returned to within normal ranges. INTERPRETATION: People with environmental exposure to waterways in which Pfiesteria toxins are present are at risk of developing a reversible clinical syndrome characterised by difficulties with learning and higher cognitive functions. Risk of illness is directly related to degree of exposure, with the most prominent symptoms and signs occurring among people with chronic daily exposure to affected waterways.

Adult↗
PubMed1998

Structure determination of the capsular polysaccharide from Vibrio vulnificus strain 6353.

Vibrio vulnificus is a pathogenic gram-negative bacterium, endemic to brackish waters, which is often isolated from sediments, from the water column or from shellfish. It is associated with wound infections and septicemia in humans and the virulence of V. vulnificus has been strongly associated with encapsulation. The capsular polysaccharide purified from a virulent strain of V. vulnificus 6353 did not show cross reactivity with antibodies to the capsular polysaccharide of a related pathogenic strain of V. vulnificus (MO6-24) the structure of which was recently reported. NMR spectroscopic analysis of the purified polysaccharide from strain 6353 showed that the polymer is composed of four sugar residues per repeating subunit including 2,6-dideoxy-2-N-acetylamino-alpha-D-glucose (QuiNAc), 2-deoxy-2-N-acetylamino-alpha-D-galactose (alpha-D-GalNAc), 2-deoxy-2-N-acetylamino-alpha-D-galcturonic acid (alpha-D-GalNAcA) and 2-N-acetylamino-alpha-D-glucuronamide (alpha-D-GlcNAcANH2). The 1H- and 13C-NMR spectra were completely assigned by homonuclear and heteronuclear NMR spectroscopy. Sugar types and anomeric configurations were determined from proton homonuclear coupling constants and glycosidic linkages were determined from 1H-13C heteronuclear multiple bond correlation spectra. Sugar identities were confirmed by high performance anion-exchange chromatography and absolute configurations were determined by gas chromatography in combination with molecular modeling and NMR spectroscopy. The structure of the polysaccharide repeating unit is: [-->4)-alpha-D-GalpNAc-(1-->3)-alpha-D-GalpNAcA-(1-->3)-alpha-D-++ +QuipNAc-(1-->]n alpha-D-GlcpNAcANH2 (1-->4)- -->. While there are some common features shared among the structures of the capsular polysaccharides of pathogenic strains of V. vulnificus, there are distinct differences in the detailed structures.

Amino Sugars↗
PubMed1998

Cochlear origin of hearing loss in MELAS syndrome.

There have been few studies investigating the mechanism and nature of the hearing loss that occurs in the mitochondrial disorders. We studied 18 patients with the MELAS A3243G point mutation from four different kindreds. Pure tone audiometry, speech discrimination testing, acoustic reflexes, tympanometry, and brain stem auditory evoked responses were performed to localize the site of pathology in the auditory pathways. In 12 patients, we performed electrocochleography and otoacoustic emissions to assess cochlear involvement. Neuroimaging and promontory nerve stimulation were performed to exclude retrocochlear pathology. Audiological testing confirmed sensorineural hearing loss in 14 of the 18 patients studied; hearing loss was usually gradual in onset, was symmetrical, and initially affected the higher frequencies. In some patients, there were features that distinguished the hearing loss from presbyacusis, including a young age at onset, asymmetrical involvement, stepwise progression, and partial recovery. We treated one patient who had profound bilateral hearing loss with cochlear implantation; this restored good functional hearing. Hearing loss in MELAS syndrome appears to be due to dysfunction of the cochlea, probably resulting from metabolic failure of the stria vascularis and outer hair cells. Cochlear implantation is a therapeutic option worth considering in those patients who become deaf.

Adolescent↗
PubMed1998

Late components of the event-related potentials and their topography in Parkinson's disease.

Late components of the event-related potential (ERP; N100, P200, N200, and P300) were elicited using an auditory oddball paradigm (with a button-press response to target stimuli) in 15 Parkinson's disease (PD) patients and 50 normal control subjects. Compared with control subjects, PD subjects showed a significant decrease in N200 amplitude. Between-group topographical differences in N200 amplitude were evident at central (C3, Cz, C4) and temporal (T5, T3, T4, T6) regions. The results may reflect a deficit in response selection in PD possibly resulting from a dysfunction associated with the abnormalities in the central and temporal regions found to have a decreased N200 amplitude compared with normal control subjects in this study.

Acoustic Stimulation↗
PubMed1998

X-linked Dystonia-Deafness syndrome.

We report a family with early-onset deafness and progressive dystonia exclusively involving males over two successive generations. There is also evidence of cognitive impairment and corticospinal tract involvement. The pedigree suggests an X-linked inheritance. A similar family was originally described by Scribanu and Kennedy. Tranebjaerg et al. have recently reported two other families with linkage to Xq22 and also proposed a novel X-linked candidate gene. These findings support the existence of a distinct neurodegenerative syndrome principally characterized by early-onset deafness and progressive dystonia. Neuropathology of one case showed a mosaic pattern of neuronal loss and gliosis in the caudate and putamen suggesting that this pattern is not restricted to XDP or Lubag.

Adult↗
PubMed1998

Maximal growth occurs at a broad range of essential amino acids to total nitrogen ratios in kittens.

Kittens fed diets containing 2.0 and 3.0 times (x) the NRC (1986) essential amino acid (EAA) requirement (EAArq) and 210 to 560 g crude protein (CP)/kg diet had growth rates and plasma amino acid patterns that were not significantly different than kittens fed a control diet (CD) containing 1.5 x EAArq and 350 g CP/kg diet. Growth rates of kittens fed diets containing only EAA (with nontoxic levels of arginine and methionine) and 280 to 460 g CP/kg diet were equivalent to those of kittens fed CD. Kittens fed only EAA and 140 and 210 g CP/kg diet had growth rates that were significantly lower than kittens fed CD. Since the growth rate of kittens fed 1.5 x EAArq and 210 g CP/kg diet in a previous experiment was equivalent to kittens fed CD (Taylor et al., 1997), it is suggested that the requirement for CP is higher (up to 280 g CP/kg diet) when only EAA are fed. The higher crude protein requirement appears to be primarily a consequence of the high obligatory nitrogen loss as urea (especially from arginine) incurred in the conversion of nitrogen from EAA to dispensable amino acids in the liver and secondarily because of a slow rate of catabolism of the EAA. A 3-dimensional plot of weight gains vs. CP levels and EAA to total nitrogen (E:T) ratios of kittens shows a broad range of CP levels and E:T ratios that support optimal growth in the kitten. It is suggested that similar patterns would occur in the chick, rat and other species if adverse effects caused by excesses of specific amino acids are avoided.

Amino Acids↗
PubMed1998

Structure of a muramic acid containing capsular polysaccharide from the pathogenic strain of Vibrio vulnificus ATCC 27562.

Vibrio vulnificus strains isolated from septicemia cases and from the environment show a wide variety of capsular types. In an attempt to find common structural features which can be correlated with pathogenicity and toxicity, we have determined structures of the capsular polysaccharides (CPS) from several pathogenic strains. We report the complete structure of the polysaccharide from the pathogenic V. vulnificus strain ATCC 27562 using a combination of homonuclear and heteronuclear one-dimensional and two dimensional NMR experiments. The 13C and 1H NMR spectra, including the exchangeable amide proton resonances, have been completely assigned. The amide linkage between Ser and C6 of GalA has been unambiguously determined by water-suppressed 2D NOESY. To verify the structure established by NMR, we have fragmented the polymer employing the Smith degradation procedure. The Smith product identified by NMR and matrix-assisted laser desorption mass spectrometry is consistent with the proposed structure for the CPS, which is composed of D-GlcNAc, MurNAc, D-GalA, L-Rha and is serine-linked as shown: [formula: see text]

Bacteremia↗
PubMed1998

Plasma aldosterone concentration of cats.

Aldosterone concentrations in the plasma of specific-pathogen-free, domestic, short-hair cats given sodium replete diets were measured by a radio-immunoassay. Plasma samples assayed were taken from male and female cats of 8, 12, 17, 20, 26, 29, 40 and > 52 weeks of age, from adult non-pregnant queens, and from queens in the ninth weeks of pregnancy and in the second and fifth week of lactation. Plasma aldosterone concentration was also measured in samples taken four times over a 24 h period (06:00-06:30, 11:00-11:30, 17:00-17:30 and 23:00-23:30) in a group of seven adult male cats. neither age nor sex had a significant effect on the plasma aldosterone concentration. Also, queens had similar aldosterone concentrations in plasma whether they were non-pregnant, pregnant, or lactating. No circadian rhythm was observed in plasma aldosterone concentrations in adult male cats. The plasma aldosterone concentrations of 148 cats (87 males and 61 females, ranging in ages from 8 to > 52 weeks) had a positive skew distribution with a median of 161 pmol l-1. The upper value for plasma aldosterone concentration in healthy domestic cats as defined by the 95 percentile was 700 pmol l-1.

Aging↗
PubMed1998

Colonization with vancomycin-resistant enterococci in chronic hemodialysis patients.

Vancomycin-resistant enterococcus (VRE) has been identified with increased frequency in dialysis populations, but the risk factors for VRE colonization are not well defined in hemodialysis patients. Patients from a university-affiliated outpatient dialysis center had surveillance stool or rectal cultures for VRE during April 1994 and January 1996. The combined cohort of 168 patients was followed-up for all-cause mortality, subsequent hospitalization, and VRE infection. Demographic and risk factor information, including age, gender, race, diabetes, coronary artery disease (CAD), and human immunodeficiency virus (HIV) infection, were collected on all patients. Sixteen patients had surveillance cultures grow vancomycin-resistant Enterococcus faecium or E faecalis (VREF), and nine additional patients had clinical cultures positive for VREF. The median follow-up time for patients with positive surveillance or clinical cultures for VREF was 421 days versus 423 days for those without VREF. Patients with positive surveillance cultures for VREF had less time on hemodialysis before screening (median = 207 days v 822 days; P < 0.01), and more hospitalization in the year before screening (median = 19 days v 3 days, P < 0.01) compared with those without VREF. Patients with VREF colonization were more likely to develop infection with VREF (25% v 1%, P < 0.01) than those without VREF colonization. However, adjusting for age, diabetes, coronary artery disease, and acquired immune deficiency syndrome (AIDS) using Cox-proportional hazards models, the presence of VREF on screening culture was not associated with increased risk of death (RR = 1.1, P = 0.86). Thus after adjusting for other comorbidities, VREF colonization was not associated with increased mortality. Patients with end-stage renal disease (ESRD) on hemodialysis who are hospitalized are more likely to have VREF, but longer duration on hemodialysis was not associated with presence of this organism. This suggests that VRE transmission occurs predominantly in the inpatient setting.

Adult↗
PubMed1998

Dysfunctions of automatic (P300a) and controlled (P300b) processing in Parkinson's disease.

P300 Event Related Potentials components (P300a and P300b) were investigated using an auditory oddball paradigm (with a button press response to target stimuli) in 15 Parkinson's disease patients and 50 normal controls whilst simultaneously measuring electrodermal activity. Cluster analysis showed that the first 10 target stimuli generated the largest skin conductance responses. The first 10 single-trial ERP epochs were therefore analysed as an ERP sub-average for each individual. The P300a component (associated with the automatic 'Orienting Reflex') was expected to be most prevalent in this sub-average (compared with sub-averages of subsequent blocks of 10 target stimuli). Twenty-nine out of 50 normal controls (58%) elicited a P300a in the first 10 target sub-average, compared with only 2 out of 15 Parkinson's disease subjects (13%). The conventional P300b component (associated with controlled processing) was found to be significantly delayed for all sub-averages for the Parkinson's disease group when compared with controls. These preliminary findings suggest a possible dysfunction in both automatic and controlled processing in this disorder.

Adult↗
PubMed1998

Vitamin B-6 deficiency and level of dietary protein affect hepatic tyrosine aminotransferase activity in cats.

Total activity [pyridoxal 5'-phosphate (PLP) added in the assay] of hepatic tyrosine aminotransferase (TAT) measured in cats at 0300, 0900, 1500 and 2100h was 10.3 +/-1.1, 14.0 +/- 0.7, 9.8 +/- 1.3 and 11.0 +/- 0.7 nkat/g liver, indicating little diurnal variation. Activity after 18 h of food deprivation was 10.0 +/- 0.3 nkat/g liver, also not different from cats that were eating ad libitum. These findings support the idea that cats have only limited changes in the activity of hepatic TAT compared with rats. Total TAT activity was measured in cats fed high protein (550 g/kg) and low protein (180 g/kg) diets for 4 wk. Cats fed a high protein diet had activities significantly higher (about twice) than cats fed the low protein diet. Hepatic TAT activity of vitamin B-6-deficient cats (diet without pyridoxine for 9 wk) was compared with cats given the same diet with 8 mg pyridoxine/kg. Total hepatic TAT activity in deficient cats was significantly (P < 0.05) lower per gram soluble or total protein (but not per gram liver) than control cats; holoenzyme activity and percentage of active enzyme in deficient cats were also significantly lower by 75 and 64%, respectively. The apparent Km of TAT from cats for tyrosine (2.1 mmol/L) was similar to that for rats (1.9 mmol/L), but higher for PLP in cats (0.16 micromol/L) than rats (0.034 micromol/L). Part of the reason for the higher plasma tyrosine in vitamin B-6-deficient cats than rats is the higher Km of TAT for PLP in cats than rats.

Animals↗