Search PubMed⌕ Search

Biomedical subjects

L Hall

Publications and source records attributed to L Hall.

At least 145 records · Page 8Linked to original sources
PubMed1991

Recognition of a single hsp-60 epitope by an entire subset of gamma delta T lymphocytes.

We can conclude that a large subset of gamma delta cells, present in both murine newborn thymus and in adult spleen, respond to the stress protein, hsp60. hsp60 seems to be stimulatory whether it is derived from a foreign pathogen such as mycobacteria, or whether it originates from the mouse's own cells. The gamma delta cells that respond to this antigen bear very similar receptors, all expressing V gamma 1 and most expressing V delta 6, although their junctional variations indicate that not all members of the subset stem from clonal expansion of only one or a few cells. The hsp60-reactive subset has not at this time been shown to "home" to an epithelial location, in contrast to other known gamma delta cell subsets, and may rather carry out its functions while in circulation. Whether the hsp60 antigen requires a "presenting" molecule remains at this point unclear, but because the gamma delta cells all respond to a synthetic peptide representing an epitope of hsp60, presentation is implied. Human gamma delta cells that respond to PPD from mycobacteria, as do the mouse hsp60-reactive gamma delta cells, have also been described, many as members of a major subset in peripheral blood, although only rarely have these been reported to respond to mycobacterial hsp60. The antigenic source in PPD for these cells has not yet been determined, but as for the mouse, a low molecular weight peptide appears to be sufficient for stimulation (P. Brennan and R. Modlin, personal communication). The PPD-reactive gamma delta cells, when their receptors have been characterized, have been found to express a V gamma 9+ chain. Some evidence indicates that these cells can also recognize self hsp60; hence, in several ways, this human subset has characteristics similar to the mouse hsp60-reactive subset. Perhaps gamma delta cells that respond to hsp60 play an important role, in both mice and humans, in the detection of transformed self cells or cells containing intracellular pathogens, that escape detection by alpha beta T cells.

Amino Acid Sequence↗
PubMed1991

An audit of the clinical use of magnetic resonance imaging of the head and spine.

An audit was undertaken of the use of magnetic resonance imaging for clinical problems of the head and spine. Using a form of simulation, two consultant clinicians were asked to assess a sequential series of 200 patients referred for magnetic resonance. The clinicians considered that 200 magnetic resonance studies could replace about 330 other imaging and neurophysiology investigations; the cost of the alternative tests approximated the cost of magnetic resonance. However, there was considerable variation between cases in the costs of investigations potentially replaced by the procedure under audit, and this variation suggests ways in which magnetic resonance might be used more cost-effectively in the future.

Brain↗
PubMed1991

Expandable venous stents for treatment of the Budd-Chiari syndrome.

The goals of treatment of the Budd-Chiari syndrome are relief of portal hypertension, relief of inferior vena cava syndrome, if present, and preservation of hepatic function. This study presents a patient with clinical resolution of the Budd-Chiari syndrome after placement of expandable metallic stents in the inferior vena cava and hepatic veins. A 26-year-old man with severe ascites and lower extremity edema but with relatively preserved hepatic function had a small gradient across a suprahepatic caval web, large gradients across an intrahepatic caval stenosis and the left hepatic vein, and an occluded right hepatic vein. Under angiographic control, web and caval stenosis were balloon-dilated, and modified Gianturco expandable metallic stents were placed in the intrahepatic vena cava. The left hepatic vein was dilated twice and a stent was placed. All gradients were completely eliminated. There were no complications and after 1 year, the stents have fully expanded without migration, edema and ascites have resolved, hepatic function has normalized, and the patient has returned to work. This new technique provides a simple, safe, effective, relatively inexpensive, and potentially long-lasting treatment for selected patients with the Budd-Chiari syndrome.

Adult↗
PubMed1990

Analysis of major androgen-regulated cDNA clones from the rat epididymis.

Four abundant cDNA clones have been isolated from a rat epididymal cDNA library. Northern blot analysis has shown that these clones partially encode 4.5 kb, 2.8 kb, 1.2 kb and 0.85 kb mRNAs and that their expression is not detectable in total RNA preparations from heart, kidney, liver or testis. Fourteen days after castration the levels of the 2.8 kb, 1.2 kb and 0.85 kb transcripts were greatly reduced whereas the 4.5 kb mRNA was undetectable. Subsequent treatment of castrated rats with testosterone for 1 day resulted in a complete restoration of the pre-castration steady-state levels of the 2.8 kb and 0.85 kb mRNAs, restoration of the 4.5 kb mRNA to 70% of pre-castration levels, and a slight over-induction of the 1.2 kb mRNA. Analyses of separate regions of the epididymal tract showed that expression of the 2.8 kb and 1.2 kb mRNAs increased towards the distal end of the epididymis, while the 4.5 kb and 0.85 kb transcripts were primarily synthesised in the caput region.

Amino Acid Sequence↗
PubMed1990

Recognition of a peptide antigen by heat shock--reactive gamma delta T lymphocytes.

Small synthetic peptides that correspond to different portions of the 65-kilodalton mycobacterial heat shock protein (Hsp65) were used to identify a putative antigenic epitope for gamma delta cells. Weaker gamma delta responses to the equivalent portion of the autologous homolog, mouse Hsp63, were also seen. The stimulatory epitope overlaps with an epitope recognized by arthritogenic alpha beta T cell clones. The data suggest that gamma delta cells have a role in autoimmune disorders and imply that these cells recognize ligands by a mechanism similar to that of alpha beta T lymphocytes, that is, in the form of small processed protein fragments bound to antigen-presenting molecules.

Amino Acid Sequence↗
PubMed1990

Metallothionein gene expression and resistance to cisplatin in human ovarian cancer.

Intracellular thiols have been proposed as mediators of resistance to alkylating agents and cisplatin. As metallothionein is the predominant protein thiol, we examined its relationship to cisplatin resistance in human ovarian cancer cell lines. A human ovarian carcinoma cell line, A2780, derived from an untreated patient, was treated with cisplatin in several ways and the induced resistance to cisplatin ranged from 13- to 68-fold. The degree of resistance was dependent upon the method of selection. The drug-resistant cell lines also developed low levels of cross-resistance to cadmium. Additional cell lines established from untreated patients or ovarian cancer patients refractory to cisplatin- and/or carboplatin-containing combination chemotherapy were studied. The most cisplatin-resistant cell lines, OVCAR-8 and -10, were from patients previously treated with intensive chemotherapy. OVCAR-8 was relatively cross-resistant to cadmium while OVCAR-10 appeared relatively sensitive. Cell lines were examined for expression of metallothionein mRNA to evaluate the relationship between cisplatin resistance, cadmium cross-resistance and metallothionein expression. Only two of the cell lines with in vitro-induced resistance to cisplatin, 2780E80 and 2780CP70B3, had detectable metallothionein mRNA. The other cell lines selected in vitro for cisplatin resistance, as well as the parental A2780 ovarian cancer cell line, showed no expression at our level of detection. There was variable expression of metallothionein among the OVCAR cell lines. Cell lines from untreated patients, OVCAR-5 and -7, did express metallothionein, while the most cisplatin-resistant cell lines, OVCAR-8 and -10, did not. We also examined cisplatin induction of metallothionein mRNA in the cell lines. Only 2780CP70B3 among the cell lines with in vitro-induced cisplatin resistance showed increased expression after short-term exposure to cisplatin. OVCAR-4 also had a slight increase in expression after exposure to cisplatin. Mouse C127 cells transfected with a bovine papilloma virus-metallothionein gene construct were compared for cisplatin sensitivity to the same cell type transfected with bovine papilloma virus alone. In this model system, metallothionein expression did not influence cisplatin cytotoxicity. On the basis of these studies, we conclude that there is no causal relationship between metallothionein expression and cisplatin resistance.

Cadmium↗
PubMed1990

Introduction of internal cysteines as conformational probes in yeast phosphoglycerate kinase.

Several mutants of yeast phosphoglycerate kinase, each containing only one internal cysteine residue, were constructed from a single mutant devoid of cysteine. These cysteines were introduced as local conformational probes in selected buried positions. The enzyme activity, conformational characteristics and stability indicated that the mutations introduced only small perturbations in the molecule. The folding-unfolding process mediated by guanidine hydrochloride under equilibrium conditions was studied by following the variations in ellipticity and the reactivity of the cysteine residue towards 5,5'-dithiobis(nitrobenzoate). The process was found to be reversible except for mutant C97A, V49C, suggesting that this region located in helix I might be crucial in determining an intermediate on the folding pathway. The transitions obtained by the two signals did not coincide, indicating that the local structures, in several parts inside the molecule, are more sensitive to the denaturant than the overall conformation.

Catalysis↗
PubMed1990

Site-directed mutagenesis of aspartic acid 372 at the ATP binding site of yeast phosphoglycerate kinase: over-expression and characterization of the mutant enzyme.

A new phosphoglycerate kinase over-expression vector, pYE-PGK, has been constructed which greatly facilitates the insertion and removal of mutant enzyme genes by cleavage at newly introduced BamHI sites. This vector has been used to prepare mutant protein in appreciable (100 mg) quantities for use in kinetic, crystallographic and NMR experiments. Aspartate 372 is an invariant amino acid residue in genes known to code for a functionally active PGK. The function of this acidic residue appears to be to help desolvate the magnesium ion complexed with either ADP or ATP when this substrate binds to the enzyme. Both crystallographic and nuclear magnetic resonance experiments show that the replacement of the residue with asparagine has only minimal effects on the overall structure. The substitution of the charged carboxyl group with that of the neutral amide affects the binding of the nucleotide substrate as predicted but not, as might have been expected, the binding of 3-phosphoglycerate. The overall velocity of the enzymic reaction (Vmax) is reduced 10-fold by the substitution of aspartic acid 372 by an asparagine residue (D372N). This reduction in Vmax is considerably less than one would expect from its known position within the structure of the enzyme. This result therefore poses questions about our understanding of charged groups at the active centres of enzymes and of the reason for their apparent conservation.

Adenosine Triphosphate↗
PubMed1990

An 18-kDa androgen-regulated protein that modifies galactosyltransferase activity is synthesized by the rat caput epididymidis, but has no structural similarity to rat milk alphalactalbumin.

Galactosyltransferase and alphalactalbumin-like activities have been reported to be present in the post-testicular fluids of the male reproductive tract. In the lactating mammary gland, these activities constitute the lactose synthetase complex. Kinetic parameters and acceptor specificities previously reported, along with recent amino acid sequence analysis argue against the mammary gland and epididymal activities being products of the same gene. In this paper we present cell-free translation of rat epididymal mRNA and Northern blot analysis of epididymal mRNA hybridized with authentic rat alpha-lactalbumin cDNA supporting this lack of identity and describe the differential synthesis and secretion of the androgen-regulated 18 kDa component of the so-called rat epididymal alphalactalbumin-like complex along the length of the epididymis. We conclude that although the 18 kDa component of the so-called epididymal alphalactalbumin moiety (E alpha LA) is capable, in common with a number of unrelated molecules, of modifying galactosyltransferase acceptor specificity in vitro, there is no primary structural similarity between it and authentic rat mammary alphalactalbumin. In view of the fact that the activity of E alpha LA is 1/100th that of authentic milk alphalactalbumin, we suggest that it may not be of physiological importance and that modification of galactosyltransferase activity may not be the function of the 18 kDa molecule.

Amino Acid Sequence↗
PubMed1990

Identification of the Epstein-Barr virus terminal protein gene products in latently infected lymphocytes.

The terminal protein (TP) gene produces two overlapping mRNAs in latently infected lymphocytes that are predicted to encode the similar polypeptides TP1 (497 amino acids) and TP2 (378 amino acids), with TP1 exon 1 providing 119 extra unique residues at the N terminus. Rabbit antisera were raised to procaryotic fusion proteins and used to detect expression of a predicted 53-kilodalton (kDa) TP product in transfected 293 cells and latently infected lymphocytes. Fractionation of transfected 293 cells showed this protein to be localized to an integral membrane preparation. The same fraction of latently infected lymphocytes contained proteins of 53 and 27 to 39 kDa as determined by Western immunoblotting with the TP-specific rabbit antisera. Immunoprecipitation of TP products from 35S-labeled human lymphoblastoid cells (CR/B95-8) was used in pulse-chase experiments and showed that TP1 was a labile protein with a half-life of approximately 2 to 4 h. The anti-fusion protein serum detected a 53-kDa TP1 and degradation products in the range of 25 to 35 kDa. A panel of Burkitt's lymphoma cell lines and cell lines established with virus recovered from the BL cells were analyzed by Western immunoblotting and found to contain the 53-kDa TP1 product, its degradation products, or both. Only two EBV-positive BL cell lines (BL72 and Wewak II) were negative in this assay. The results suggest that a labile TP1 protein may be expressed by most, if not all, EBV-infected cell lines.

Antibodies, Monoclonal↗
PubMed1990

Spatial distribution of mRNAs for myelin proteins in primary cultures of mouse brain.

A nonradioactive in situ hybridization procedure was employed to study the distribution of mRNAs for myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in oligodendrocytes in primary cultures of mouse brain. This procedure provided good cellular localization and allowed rapid detection of the mRNAs with low backgrounds. Gradual movement of MBP mRNAs from oligodendrocyte somas into processes was observed with time in culture. The MBP mRNAs were observed to be distributed in an asymmetric fashion within the somas and cell processes. Antigalactocerebroside staining indicated the presence of oligodendrocyte processes prior to movement of MBP mRNA, suggesting that the presence of processes alone was insufficient for translocation of MBP mRNAs. The mRNAs for PLP and MAG remained confined to the oligodendrocyte somas at all times in culture at least up to 28 days. While most of the CNP mRNAs were observed to be associated with the perikarya of oligodendrocytes, in less than 1% of these cells the presence of CNP mRNA in the processes was evident. This suggests that there may exist a subset of oligodendrocytes in which the translocation of these messages occurs.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1990

Length of hospital stay in veteran surgical service patients with nosocomial infections.

Four hundred ninety-nine nosocomial infections (with 657 isolates) in 288 Surgical Service patients were monitored from February 1986 to June 1987 (17 months) to determine the influence that pathogen or site of infection had on the length of hospital stay. Patients with upper respiratory and skin infections were more likely to have significantly longer length of stay than those with infections in other sites. Infections with Haemophilus influenzae and Pseudomonas aeruginosa were more likely to yield longer culture to discharge periods than other organisms in certain settings. Extended lengths of stay were common in patients with nosocomial infections.

Cross Infection↗
PubMed1989

Site-directed mutagenesis of histidine 62 in the 'basic patch' region of yeast phosphoglycerate kinase.

Site-directed mutagenesis has been used to produce a mutant form of yeast phosphoglycerate kinase (PGK) in which the 'basic patch' residue His 62 has been replaced by a glutamine residue. Using 1H-NMR spectroscopy, it was found that 3-phosphoglycerate (3-PG) binding to the mutant protein induces the same conformational effects as for wild-type PGK, although the affinity was reduced by 2- to 3-fold. Kinetic studies show both Km for 3-PG and Vmax to be increased by approximately 2-fold relative to the wild-type enzyme. These data are consistent with the suggestion that His 62 assists in the binding of the substrate to the enzyme.

Histidine↗
PubMed1989

Study of the fast-reacting cysteines in phosphoglycerate kinase using chemical modification and site-directed mutagenesis.

Horse muscle phosphoglycerate kinase, like other mammalian phosphoglycerate kinases, contains seven cysteine residues of which two react rapidly with 5,5'-dithio-bis(2-nitrobenzoate) (Nbs2) following second-order kinetics (k = 640 M-1.s-1). Selective cyanylation of the fast-reacting cysteines, followed by chemical cleavage and subsequent sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis of the resulting polypeptides, suggested that these cysteines are at positions 378 and 379. Cysteine residues were introduced into yeast phosphoglycerate kinase by site-directed mutagenesis. Mutant enzymes, each containing only one cysteine residue at position 364, 376, or 377, were constructed from a mutant devoid of cysteine (Cys97----Ala). In the last two mutants, the cysteines were at positions corresponding to Cys378 and Cys379, respectively, in the horse muscle enzyme. The chemical reactivity of the cysteine groups in these latter two yeast mutant enzymes was similar to that of the fast-reacting cysteines in the horse muscle enzyme. Furthermore, they were similarly modified upon substrate binding. All these data demonstrate unambiguously that the fast-reacting cysteines in the horse muscle enzyme are Cys378 and Cys379.

Animals↗
PubMed1989

One- and two-dimensional NMR studies of yeast phosphoglycerate kinase.

One- and two-dimensional proton NMR studies have been carried out on yeast phosphoglycerate kinase (Mr approximately 45,000) in order to identify amino-acid spin systems and obtain sequence-specific assignments. A number of sequence-specific assignments have been made using a combination of structural information contained in nuclear Overhauser effect spectra and X-ray crystallographic data. The results of substrate binding studies (both 3-phosphoglycerate and Mg.ATP), which indicate mutual reorientation of certain assigned aromatic residues in the inter-domain region of the protein, are discussed.

Adenosine Triphosphate↗