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Biomedical subjects

B Jann

Publications and source records attributed to B Jann.

At least 19 recordsLinked to original sources
PubMed1998

Neuropharmacologic treatment of hemineglect: a case report comparing bromocriptine and methylphenidate.

Individuals who have hemineglect fail to attend to stimuli presented on the side of the body contralateral to a brain lesion. Although in animal studies the severity of neglect correlates with the degree of dopamine depletion, in hemineglect patients dopamine-enhancing medications have produced inconsistent results. We present a case of hemineglect following a right cerebrovascular accident in a 68-year-old man treated consecutively with methylphenidate and bromocriptine. Tests sensitive to neglect were administered during treatment with methylphenidate, then after all medications had been discontinued, then when the patient was taking low and moderate doses of bromocriptine, and again after all medications had been discontinued for 4 and 26 days. Methylphenidate was superior to no drug treatment. Bromocriptine produced more improvement in neglect than methylphenidate. Although the patient showed an exacerbation of his neglect after withdrawal from methylphenidate, performance gains persisted after withdrawal from bromocriptine. Treatment effects appear related to medication choice, timing of drug treatment, and the adaptability of dopaminergic receptor systems.

Brain Damage, Chronic↗
PubMed1998

Organization of responses in human lateral gastrocnemius muscle to specified body perturbations.

There is mounting evidence that human muscles have discrete partitions. In an effort to accurately assess how the control to each of the three heads (designated as A-C) of the lateral gastrocnemius (LG) muscle might be organized, we performed exploratory studies in five subjects each of whom was provided 30 random angular and linear perturbations while standing on a balance platform in each of three experiments. The responses from each LG head were recorded with strategically-placed fine-wire electrodes and, after correction for variation in distance to each recording site, latency to activation and the sequence of recruitment for each LG head were determined. Within individual subjects, the same LG head was first recruited. The C-head was recruited first during linear perturbations between subjects and across sessions, but the overall recruitment pattern was different between subjects. The fact that a consistent, selective response was seen during dynamic linear but not angular perturbations suggests that a more consistent strategy of inter-partition response may be engaged for the former perturbation. This behaviour may be caused by use of the LG C-head to assist the medial gastrocnemius to control ankle plantar flexion and pronation during the shearing forces generated with linear translations. Further exploration into the relationship between selective activation of muscle partitions in the presence of defined movement conditions appears justified.

Adolescent↗
PubMed1996

Analysis of the enzymatic cleavage (beta elimination) of the capsular K5 polysaccharide of Escherichia coli by the K5-specific coliphage: reexamination.

The capsular K5 polysaccharide of Escherichia coli is the receptor of the capsule-specific coliphage K5, which harbors an enzyme that degrades the capsular K5 polysaccharide to a number of oligosaccharides. Analysis of the degradation products using gel permeation chromatography, the periodate-thiobarbituric acid and bicinchoninic acid reactions, and nuclear magnetic resonance spectroscopy showed that the major reaction products are hexa-, octa-, and decasaccharides with 4,5-unsaturated glucuronic acid (delta4,5GlcA) at their nonreducing end. Thus, the bacteriophage enzyme is a K5 polysaccharide lyase and not, as we had reported previously, an endo-N-acetylglucosaminidase.

Bacterial Capsules↗
PubMed1995

NMR investigation of the 6-deoxy-L-talose-containing O45, O45-related (O45rel), and O66 polysaccharides of Escherichia coli.

The structures of the 6-deoxytalose-containing O-specific polysaccharides from the O45 antigen, an O45-related antigen (O45rel), and the O66 antigen (lipopolysaccharides, LPSs) of Escherichia coli were elucidated by chemical characterization and by one- and two-dimensional 1H and 13C NMR spectroscopy. The O45 and O45-related polysaccharides have the following general structure: [formula: see text] For the O45 antigen, X is alpha-D-FucpNAc and for the O45-related antigen, X is beta-D-GlcpNAc. The structure of the O66 polysaccharide is [formula: see text]

Carbohydrate Conformation↗
PubMed1995

NMR reinvestigation of two N-acetylneuraminic acid-containing O-specific polysaccharides (O56 and O24) of Escherichia coli.

Structures for the N-acetylneuraminic acid (Neu5Ac)-containing O56 and O24 polysaccharides of Escherichia coli have been reported previously. During these studies unusual chemical shifts had been observed for the NMR signals for H-3eq and C-3 of the Neu5Ac residues of both polysaccharides. In further pursuing this phenomenon, we have reinvestigated the O56 and O24 polysaccharides as well as derived oligosaccharides by one- and two-dimensional NMR spectroscopy. The results showed that structures of both polysaccharides (PSs) had to be modified and formulated as [formula: see text] 2D ROESY spectra revealed a strong NOE between H-3eq of Neu5Ac and the protons of the side-chain sugar (H-3 and H-5 of alpha-D-Gal p in the O56 PS and H-3 of alpha-D-Glc p in the O24 PS) and also between H-3ax of Neu5Ac and H-3 of beta-D-Glc p in the main chain. This indicated a close spatial association of the seven-linked alpha-Neu5Ac and the side-chain residues alpha-D-Gal p (O56 PS) and alpha-D-Glc p (O25 PS), respectively. The strong long-range spatial contacts caused the unusual chemical shifts of H-3eq and C-3 of Neu5Ac.

Acetylgalactosamine↗
PubMed1994

Structure of the O16 polysaccharide from Escherichia coli O16:K1: an NMR investigation.

The polysaccharide moiety of the O16 antigen (lipopolysaccharide) consists of D-glucopyranose, D-galactofuranose, L-rhamnopyranose, and 2-acetamido-2-deoxy-D-glucopyranose in the molar ratios 1:1:1:1. It is O-acetylated with one acetyl group per repeating unit. One- and two-dimensional NMR spectroscopy of the polysaccharide before and after O-deacetylation showed that the O16 polysaccharide has the structure [formula: see text]

Carbohydrate Conformation↗
PubMed1994

Regulation of Escherichia coli K5 capsular polysaccharide expression: evidence for involvement of RfaH in the expression of group II capsules.

Expression of the Escherichia coli K5 antigen was used as a model system to study the role of known regulators of gene expression on production of group II capsules in E. coli. Only mutations in the rfaH gene had an effect on production of the K5 antigen, abolishing the expression of any detectable capsule at 37 degrees C. None of the mutations studied induced capsule expression at 18 degrees C. A sequence, termed JUMPstart, found in group II capsule gene clusters and upstream of a number of polysaccharide biosynthesis genes in enteric bacteria is homologous to sequences found in RfaH regulated operons. This may indicate a common mode of regulation of these polysaccharide biosynthesis genes by RfaH.

Antigens, Bacterial↗
PubMed1994

Structural comparison of the O6 specific polysaccharides from E. coli O6:K2:H1, E. coli O6:K13:H1, and E. coli O6:K54:H10.

Two distinct forms of the O6 antigen (LPS) from E. coli were analysed using 1H and 13C NMR spectroscopy. Their structures were found to be [formula: see text] In the O6-specific polysaccharide from E. coli O6:K2 and O6:K13, X is beta-D-Glc p, as had previously been shown for the O6 polysaccharide from E. coli O6:K15; in the O6 specific polysaccharide from E. coli O6:K54, X is beta-D-Glc pNAc.

Carbohydrate Conformation↗
PubMed1994

Structure of the O83-specific polysaccharide of Escherichia coli O83:K24:H31.

The polysaccharide moiety of the O83 antigen (lipopolysaccharide, LPS) consists of D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and D-glucuronic acid in the molar ratios 1:2:1:1. Methylation analysis of the polysaccharide and derived oligosaccharides as well as one- and two-dimensional 1H and 13C NMR spectroscopy of the polysaccharide at pD 1 and 6 showed that the O83 polysaccharide has the primary structure-->6)-alpha-D-Glc p-(1-->4)-beta-D-Glc pA-(1-->6)-beta-D-Gal p-(1-->4)-beta-D- Gal p-(1-->4)-beta-D-Glc pNAc-(1-->.

Antigens, Bacterial↗
PubMed1994

Genetic analysis of Escherichia coli O9 rfb: identification and DNA sequence of phosphomannomutase and GDP-mannose pyrophosphorylase genes.

Subcloning, transposon insertion, and deletion analysis revealed that the Escherichia coli O9 rfb region is about 12 kb in size. The region encodes at least seven polypeptides of 89, 74, 55, 50, 44, 41 and 39.5 kDa. Southern hybridization analysis of rfb regions of E. coli O8 and O9, and Klebsiella O3 and O5 serotypes (all of these O polysaccharides are mannose homopolymers and the structures of the repeating unit of E. coli O9 and Klebsiella O3 are identical) showed that a central region specific for E. coli O9 and Klebsiella O3 is flanked by two regions common to all four. Complementation experiments using strains with known defects and specific tests for the enzymic activity showed that the 50 and 55 kDa polypeptides, encoded by the common region, are phosphomannomutase (PMM) and GDP-mannose pyrophosphorylase (GMP), respectively. Nucleotide sequencing of the region revealed the presence of two genes, rfbK and rfbM, analogous to the corresponding genes of Salmonella typhimurium. In E. coli O9, rfbK and rfbM encode proteins of 460 amino acids (50,809 Da) and 471 amino acids (52,789 Da). The amino acid sequence of GMP was conserved in RfbMs of E. coli O7 and Salmonella groups B, C1 and C2, CpsB of S. typhimurium, AlgA of Pseudomonas aeruginosa, and XanB of Xanthomonas campestris. The phylogenetic trees of PMM and GMP were different in topology and in the evolutionary distances from ancestors.

Amino Acid Sequence↗
PubMed1994

Neurobehavioural consequences of closed head injury in older adults.

This study examined the neurobehavioural effects of closed head injury (CHI) in adults aged 50 years and older. Twenty two mild to moderate CHI patients who were within seven months of the injury were administered measures of language, memory, attention, and executive functioning. Compared with demographically similar normal controls, the patients exhibited significantly poorer functioning on the cognitive domains. Naming and word fluency under timed conditions, verbal and visual memory, and the ability to infer similarities were especially vulnerable. These initial findings indicate that CHI in older adults produces considerable cognitive deficits in the early stages of recovery. Future research should characterise long term outcome and the potential links between head injury and the development of progressive dementia.

Age Factors↗
PubMed1993

Synthesis of the K5 (group II) capsular polysaccharide in transport-deficient recombinant Escherichia coli.

The genes directing the expression of group II capsules in Escherichia coli are organized into three regions. The central region 2 is type specific and thought to determine the synthesis of the respective polysaccharide, whilst the flanking regions 1 and 3 are common to all group II gene clusters and direct the surface expression of the capsular polysaccharide. In this communication we analyze the involvement of region 1 and 3 genes in the synthesis of the capsular KS polysaccharide. Recombinant E. coli strains harboring all KS specific region 2 genes and having various combinations of region 1 and 3 genes were studied using immunoelectron microscopy. Membranes from these bacteria were incubated with UDP[14C]GlcA and UDPGlcNAc in the absence or presence of KS polysaccharide as an exogenous acceptor. It was found that recombinant strains with only gene region 2 did not produce the K5 polysaccharide. Membranes of such strains did not synthesize the polymer and did not elongate K5 polysaccharide added as an exogenous acceptor. An involvement of genes from region 1 (notably kpsC and kpsS) and from region 3 (notably kpsT) in the K5 polysaccharide synthesis was apparent and is discussed.

Antigens, Bacterial↗
PubMed1993

Structure of the O-specific polysaccharide of the O23 antigen (LPS) from Escherichia coli O23:K?:H16.

The polysaccharide moiety of the O23 antigen (lipopolysaccharide) consists of D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-galactose in the molar ratios 2:1:2:1. Methylation analysis of the polysaccharide as well as one- and two-dimensional 1H and 13C NMR spectroscopy of the polysaccharide and a trisaccharide obtained by Smith degradation showed that the O23 polysaccharide has the primary structure [formula: see text].

Carbohydrate Conformation↗
PubMed1993

Structural comparison of the O4-specific polysaccharides from E. coli O4:K6 and E. coli O4:K52.

Two distinct forms of the O4 antigen (LPS) from E. coli were analysed by 1H and 13C NMR spectroscopy. Both consisted of D-glucose, L-rhamnose, 2-acetamido-2,6-dideoxy-L-galactose (L-FucNAc), and 2-acetamido-2-deoxy-D-glucose. Their structures were found to be [formula: see text]. In the O4-specific polysaccharide from E. coli O4:K3, O4:K6, and O4:K12, X is alpha-D-Glcp. In the O4 specific polysaccharide from E. coli O4:K52, the rhamnose residue is not substituted (X = H).

Carbohydrate Conformation↗