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Biomedical subjects

L Hall

Publications and source records attributed to L Hall.

At least 73 records · Page 4Linked to original sources
PubMed1997

Comparative effects of clindamycin and ampicillin on superantigenic activity of Streptococcus pyogenes.

We have tested the ability of Streptococcus pyogenes to produce streptococcal pyrogenic exotoxin A (SPEA) and superantigenic activity in the presence of sub-inhibitory concentrations of ampicillin and clindamycin. After 6 h of culture, SPEA production by S. pyogenes was higher in broths containing ampicillin (715.7 +/- 296.4 pg/10(6) cfu) than in broths containing clindamycin (167.1 +/- 31.9 pg/10(6) cfu), a difference that was not significant (P = 0.25). Promitogenic activity of bacterial supernatants was also greater in ampicillin-treated cultures (467.5 +/- 17.2 ccpm/10(6) cfu) than in clindamycin-treated cultures (169.2 +/- 8.9 ccpm/10(6) cfu), a difference that was highly significant (P = 0.0001). The data support the use of clindamycin in the treatment of streptococcal toxic shock-like syndrome, in order to inhibit superantigen synthesis.

Ampicillin↗
PubMed1997

Correlation between in-vitro susceptibility testing to itraconazole and in-vivo outcome of Aspergillus fumigatus infection.

Given the increased choice of therapeutic agents and the rising incidence of serious invasive disease, it is important that reliable in-vitro methods for detecting antifungal drug resistance in Aspergillus spp. are developed. Six clinical isolates of Aspergillus fumigatus, obtained from patients in whom the clinical outcome was known, were selected for study. Each was used to examine a range of parameters affecting agar dilution and broth microdilution susceptibility test results. The in-vitro results were compared with outcome in a neutropenic mouse model of invasive aspergillosis. Groups of animals were treated with itraconazole at 25 mg/kg and 75 mg/kg and survival rates and organ burdens were determined. Itraconazole was efficacious against four isolates (susceptible) but failed for two (resistant) in the animal model of infection. Both the resistant isolates had been obtained from patients receiving itraconazole treatment with good serum concentrations of the drug. Conditions for the agar dilution test which produced results that correlated best with our in-vivo observations included the use of RPMI agar with L-glutamine buffered to pH 7 with MOPS, inoculated with 10(6)-10(7) conidia/mL and incubated for 48-72 h at 28 or 35 degrees C with a no-growth endpoint. Optimal conditions for the broth microdilution method included the use of RPMI medium with L-glutamine and 2% glucose buffered to pH 7 with MOPS, an inoculum of 2 x 10(5) conidia in 200 microL incubated for 48 h at 35 degrees C with a growth (or trace) endpoint. The MICs for the susceptible isolates were 0.12-1.0 mg/L and > or = 16 mg/L for the resistant isolates. With careful selection and standardization of test conditions it is possible to generate reproducible in-vitro susceptibility data for Aspergillus spp. that will predict clinical outcome.

Animals↗
PubMed1997

The detection and confirmation of 11 beta-hydroxysteroid dehydrogenase type 1 transcripts in human luteinized granulosa cells using RT-PCR and plasmid pUC18.

The activity of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) in human granulosa cells has been shown to be associated with the outcome of treatment following in-vitro fertilization and embryo transfer. There are two known isoforms of 11 beta-HSD which differ significantly in their actions and co-factor requirements. The net activity of 11 beta-HSD which differ significantly in their actions and co-factor requirements. The net activity of 11 beta-HSD within the human ovary is unclear, but may be of particular importance within the ovarian follicle in regulating possible glucocorticoid influences on the oocyte. This study presents preliminary information regarding establishment of techniques to identify transcripts of the 11 beta-HSD isoforms within human granulosa cells and human cumulus cells using reverse transcription-polymerase chain reaction. In view of the high expression of the type 1 11 beta-HSD isoform and the possibility of other 11 beta-HSD isoforms in the ovary, plasmid technology was used to confirm the technique specifically identifying the known isoforms.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1997

Cloning and sequence analysis of rat fertilin alpha and beta--developmental expression, processing and immunolocalization.

Fertilin alpha and beta are members of the MDC (metalloproteinase-like, disintegrin-like, cysteine-rich) protein family and are expressed on the sperm surface where they have been proposed to play a role in mammalian fertilization. Inhibition of sperm-oocyte binding and sperm-oocyte fusion make fertilin an attractive target for the development of an immunocontraceptive vaccine. Full-length cDNAs encoding alpha and beta fertilin subunits were isolated from a rat testis cDNA library and sequenced. Using reverse transcription-polymerase chain reaction (RT-PCR), the developmental expression of fertilin alpha and beta was determined in pre-pubertal and mature rat testes. Fertilin alpha mRNA was present at all stages of development, suggesting that it is not exclusively expressed in post-meiotic germ cells. In contrast, fertilin beta mRNA was first identified in day 19 testes, coincident with the presence of pachytene spermatocytes. Polyclonal antisera raised against a 28-residue peptide (corresponding to part of the disintegrin domain) and two recombinant fusion proteins identified a 90 kDa protein in testicular sperm extracts and a 60 kDa protein in caput and cauda epididymidal sperm extracts, the predicted sizes for rat fertilin beta precursor and mature protein respectively. Indirect immunofluorescence using the anti-peptide antisera stained the acrosomal cap of permeabilized testicular, caput and caudal spermatozoa and elongating spermatids in testicular sections.

ADAM Proteins↗
PubMed1996

Molecular cloning and characterization of rat sperm surface antigen 2B1, a glycoprotein implicated in sperm-zona binding.

The rat sperm surface antigen, 2B1, that has been proposed to play a key role in sperm adhesion to the zona pellucida, has been cloned and its entire cDNA sequenced. Northern blot analysis indicates that 2B1 is encoded by a 2.2-kb RNA transcript that is abundantly expressed in the testis. The deduced protein sequence contains 512 amino-acid residues with a strong candidate signal sequence and C-terminal transmembrane domain. Data base searches reveal a high degree of sequence similarity to guinea pig, rabbit, monkey, and human PH20 sperm surface antigens, and a lower degree of similarity to honey bee and whiteface hornet venom hyaluronidases. Rat 2B1 antigen also possesses hyaluronidase activity, suggesting that it is a bifunctional protein with putative roles in the dispersion of cumulus oophorus cells as well as zona adhesion. However, while it would appear that 2B1 is the rat homologue of the guinea pig PH20 antigen, they differ in a number of important biochemical respects (including their mode of attachment to the sperm membrane and distribution between soluble and membrane-bound fractions), as well as in their localization on the sperm membrane. Expression of regions of the 2B1 protein in recombinant bacterial cells has allowed a preliminary mapping of the 2B1 epitope, and has provided more definitive information on the endoproteolytic processing of 2B1 during epididymal transit.

Amino Acid Sequence↗
PubMed1996

Sequence analysis and immunolocalisation of phosphatidylethanolamine binding protein (PBP) in human brain tissue.

We have cloned and sequenced cDNA corresponding to human brain phosphatidylethanolamine binding protein (PBP) and have used the resultant data to generate PBP-specific anti-peptide antisera for immunohistochemical studies. The distribution of PBP was assessed immunohistochemically in sections from multiple regions of neonatal brain and spinal cord, including spinal nerve roots. Strong PBP immunoreactivity was present in the cytoplasm of oligodendrocytes in the white matter and Schwann cells in the nerve roots. There was only weak immunostaining within the neurones and neuropil. The findings are in keeping with a role for PBP in the organisation of phospholipids in the myelin sheath.

Base Sequence↗
PubMed1996

Quinolone arthropathy in immature rabbits treated with the fluoroquinolone, PD 117596.

To study the potential of the fluorquinolone, PD 117596 to cause arthropathy in experimental animals, immature rabbits were orally administered the drug for five days at 0, 100, 350, 500 and 750 mg/kg. Characterization of changes induced in major synovial joints was based on: macroscopic and histopathologic observations, transmission electron microscopic examinations and magnetic resonance imaging. Preferentially targeting the knee, PD 117596 produced vesicles and erosions in articular cartilage which resembled, morphologically, those described in other laboratory species. Lesion incidence was not clearly dose-related. In the perivesicular region, degenerate chondrocytes were intermixed with hypertrophic cartilage cells and chondrocyte clusters. Ultrastructurally, hypertrophic chondrocytes were the consequence of karyomegaly and RER proliferation. Matrix density was reduced due to collagen and proteoglycan loss. Joint structures were readily visualized by magnetic resonance imaging which identified thickened articular cartilage, surface irregularities consistent with ruptured vesicles and separation of opposing articular surfaces secondary to synovival effusions. The immature rabbit, although less sensitive than the juvenile dog to the arthropathic effects of quinolones, was nonetheless a good model to study this experimental osteoarticular disease.

Animals↗
PubMed1996

Indocyanine green videoangiography of older patients with central serous chorioretinopathy.

PURPOSE: The authors studied the indocyanine green (ICG) videoangiography findings of central serous chorioretinopathy (CSC) in older adults. BACKGROUND: Central serous chorioretinopathy in older adults may be confused with the exudative forms of age-related macular degeneration (AMD) because the two entities may have similar ophthalmoscopic and fluorescein angiographic findings. Because of its enhanced ability to image the choroidal circulation, ICG videoangiography has been used to describe certain choroidal vascular abnormalities in young adults with CSC, as well as older patients with choroidal neovascularization (CNV). The ICG videoangiography findings in CSC in older adults is largely unknown. METHODS: The authors performed ICG videoangiography on 36 patients aged 50 years or older with CSC to characterize their findings. RESULTS: The ICG videoangiography findings of the patients were consistent, revealing choroidal vascular hyperpermeability manifested by areas of hyperfluorescence that were first seen in the midphase of the angiogram. In the later phases of the angiogram, there were dispersion of the hyperfluorescence and a distinctive silhouetting of the larger choroidal vessels. CONCLUSIONS: Older patients with CSC have a unique temporal and topographic pattern of hyperpermeability that can help establish the proper diagnosis.

Aged↗
PubMed1996

Platelet activating factor: release from colonic mucosa in patients with ulcerative colitis and its effect on colonic secretion.

Inflammatory mediators have been implicated in the pathophysiology of ulcerative colitis. They may stimulate intestinal secretion and contribute to the production of diarrhoea. Platelet activating factor (PAF) may be responsible for a high proportion of this secretory response. Biopsy specimens from inflamed and quiescent mucosa of patients with ulcerative colitis and normal human colonic mucosa were cultured or co-cultured. The release of PAF, prostaglandin E2, and leukotriene D4 into the culture medium was measured and the ability of this culture medium, from inflamed and normal tissues, to influence secretion in rat colonic mucosa was assessed. PAF was liberated by inflamed tissue. Its release from quiescent but not normal tissue was stimulated by medium in which inflamed mucosal biopsy tissues had been cultured and by exogenous bradykinin and 5-hydroxytryptamine, but not by histamine. PAF stimulated eicosanoid production. The rise in short circuit current produced in vitro by inflamed tissue culture medium was inhibited by the PAF receptor antagonist (CV 6209) (46%) (32.4 (2.9) v 17.5 (1.19) muA.cm-2, p < 0.005) and further by combined cyclooxygenase and lipoxygenase inhibition (indomethacin plus ICI 207968) (58%) (32.4 (2.9) v 13.6 (1.9) muA.cm-2, p < 0.005). Mepacrine and hydrocortisone attenuated considerably the electrical response evoked by medium from inflamed mucosa to a similar extent (32.4 (2.9) v 6.3 (1.2) v 5.1 (0.9) muA.cm-2, p < 0.001). These data suggest that PAF accounted for 46% of the culture medium secretory effect. Thus, any attempt to block its release in patients with ulcerative colitis may have only a partial effect on their symptoms.

Adult↗
PubMed1996

Testicular biosynthesis and epididymal endoproteolytic processing of rat sperm surface antigen 2B1.

Binding of mammalian spermatozoa to the zona pellucida of homologous eggs is mediated by specific molecules on their surface membranes. In the present investigation we describe the biogenesis, epididymal processing and cellular distribution of a plasma membrane antigen (2B1) on rat spermatozoa that has a potential role in mediating zona binding. 2B1 is expressed postmeiotically in the testis as a precursor glycoprotein (approximately 60 kDa) that first appears on the plasma membrane of stage 6 to 8 round spermatids. Northern and western blot analyses show that there is a close correlation between the timing of transcription and expression of the glycoprotein on the cell surface. During spermatid elongation 2B1 is excluded from the head domain and is sequestered onto the sperm tail. As spermatozoa pass through the caput epididymidis 2B1 is endoproteolytically cleaved at a specific arginine residue (Arg 312) to produce a heterodimeric glycoprotein (approximately 40 kDa and approximately 19 kDa) containing intramolecular disulphide bridges. Endoproteolysis at Arg 312 also takes place during culture of washed testicular or caput spermatozoa in vitro and can be prevented by serine proteinase inhibitors or enhanced by trypsinisation. However, neither processing in vivo or in vitro has any effect on the domain organisation of 2B1 antigen i.e. it remains localised to the tail. These results support the hypothesis that sperm antigens that are important for fertilization are synthesized as precursor molecules in the testis and are then "activated' during epididymal maturation and capacitation, thereby ensuring that they only become fully functional at the site of fertilization.

Animals↗
PubMed1995

Analysis of transcripts encoding novel members of the mammalian metalloprotease-like, disintegrin-like, cysteine-rich (MDC) protein family and their expression in reproductive and non-reproductive monkey tissues.

A number of sequence-related, cysteine-rich proteins containing metalloprotease-like and disintegrin-like domains (the MDC protein family), at least one of which has been shown to play a role in egg recognition during fertilization, are abundantly expressed in the mammalian male reproductive tract. In this paper we report the cloning and sequence analysis of three closely related isoforms of a novel member of this family which are expressed not only in the testis, but also in the liver, albeit at a lower level. Using a PCR-based approach we also demonstrate the presence of transcripts encoding additional, novel, disintegrin-containing proteins, in the liver and epididymis. We conclude that while some members of the MDC family are specific to the reproductive tract, suggesting functions peculiar to those tissues, others have a broader tissue distribution and may therefore play a more general role in integrin-mediated cell-cell recognition, adhesion or signalling.

ADAM Proteins↗
PubMed1995

Molecular cloning and deduced amino acid sequences of the alpha- and beta- subunits of mammalian NAD(+)-isocitrate dehydrogenase.

A 153 bp fragment of the cDNA encoding the beta-subunit of pig heart NAD(+)-isocitrate dehydrogenase (NAD(+)-ICDH) was specifically amplified by PCR, using redundant oligonucleotide primers based on partial peptide sequence data [Huang and Colman (1990) Biochemistry 29, 8266-8273]. This PCR fragment was then used as a probe to isolate cDNA clones encoding the complete mature form of the beta-subunit from a monkey testis cDNA library. Examination of the deduced amino acid sequence of the monkey subunit and the partial sequence of the pig heart enzyme revealed a high level of sequence conservation. In addition, 3 overlapping fragments of the cDNA for the alpha-subunit of monkey NAD(+)-ICDH were amplified using oligonucleotide primers derived from the cDNA sequence of a subunit of bovine NAD(+)-ICDH (EMBL accession no: U07980). These cDNA fragments allow deduction of the amino acid sequence of the alpha-subunit. Since the gamma-subunit of monkey NAD(+)-ICDH has already been cloned [Nichols, Hall, Perry and Denton (1993) Biochem. J. 295, 347-350], a deduced amino acid sequence is now available for all three subunits of mammalian NAD(+)-ICDH. Interrelationships between these subunits are discussed and they are compared with the two subunits of yeast NAD(+)-ICDH and Escherichia coli NADP(+)-ICDH.

Amino Acid Sequence↗
PubMed1995

Eukaryotic methionyl aminopeptidases: two classes of cobalt-dependent enzymes.

Using partial amino acid sequence data derived from porcine methionyl aminopeptidase (MetAP; methionine aminopeptidase, peptidase M; EC 3.4.11.18), a full-length clone of the homologous human enzyme has been obtained. The cDNA sequence contains 2569 nt with a single open reading frame corresponding to a protein of 478 amino acids. The C-terminal portion representing the catalytic domain shows limited identity with MetAP sequences from various prokaryotes and yeast, while the N terminus is rich in charged amino acids, including extended strings of basic and acidic residues. These highly polar stretches likely result in the spuriously high observed molecular mass (67 kDa). This cDNA sequence is highly similar to a rat protein, termed p67, which was identified as an inhibitor of phosphorylation of initiation factor eIF2 alpha and was previously predicted to be a metallopeptidase based on limited sequence homology. Model building established that human MetAP (p67) could be readily accommodated into the Escherichia coli MetAP structure and that the Co2+ ligands were fully preserved. However, human MetAP was found to be much more similar to a yeast open reading frame that differed markedly from the previously reported yeast MetAP. A similar partial sequence from Methanothermus fervidus suggests that this p67-like sequence is also found in prokaryotes. These findings suggest that there are two cobalt-dependent MetAP families, presently composed of the prokaryote and yeast sequences (and represented by the E. coli structure) (type I), on the one hand, and by human MetAP, the yeast open reading frame, and the partial prokaryotic sequence (type II), on the other.

Amino Acid Sequence↗
PubMed1995

Cloning and analysis of monkey fertilin reveals novel alpha subunit isoforms.

The fertilin complex, a heterodimeric surface membrane glycoprotein found on the head region of mammalian spermatozoa, has been reported to mediate membrane fusion with the egg plasma membrane during fertilization. We have employed PCR to generate products corresponding to monkey (Macaca fascicularis) fertilins from testis cDNA. These PCR products have been used to isolate full-length fertilin cDNA clones corresponding to both alpha and beta subunits. Both monkey fertilin alpha and beta cDNAs encode proteins which belong to an expanding family of metalloproteinase-like, disintegrin-like, cysteine-rich, mammalian proteins. Surprisingly, cDNAs for two fertilin alpha isoforms, alpha I and alpha II, were isolated, encoding proteins of 905 and 825 residues respectively. The predicted fertilin alpha isoforms share extensive identity, but differ significantly towards their N- and C-termini, suggesting the possibility of more than one type of fertilin complex in primates. Alignment of monkey alpha and beta fertilins with their respective guinea-pig counterparts suggests a high level of overall structural conservation throughout, whilst providing new insights into the domain function of each.

ADAM Proteins↗
PubMed1995

The monkey ESP14.6 mRNA, a novel transcript expressed at high levels in the epididymis.

A screening strategy designed to identify cloned cDNAs encoding abundant Macaca fascicularis epididymal transcripts has yielded a clone corresponding to a 1.03-kb transcript present at high levels in the epididymis. Following library rescreening, DNA sequence analysis of several near full-length clones predicts a novel, 151-amino-acid protein, epididymal secretory protein 14.6 (ESP14.6), which contains a strong candidate signal peptide characteristic of secretory proteins.

Amino Acid Sequence↗
PubMed1995

Multiple determinants for growth of human immunodeficiency virus type 1 in monocyte-macrophages.

Attempts to define the genetic determinants required for efficient growth of human immunodeficiency virus type 1 (HIV-1) in monocyte-macrophages were made by constructing chimeras between two infectious clones of HIV-1 (HXB2 and LW/C), which despite only minor differences in their DNA sequence have striking differences in cell tropism. Although both of them replicate efficiently in peripheral blood mononuclear cells, HXB2 replicates extensively in permanent T cell lines but poorly in primary monocyte macrophages (T cell line tropic); the reverse is true for LW/C (macrophage tropic). The envelope proved to contain the major determinants of macrophage tropism. However, tropism determinants appeared to be scattered along the envelope. In particular, the V3 loop alone appeared to be neither necessary nor sufficient for growth in macrophages. Both vpr and nef genes appeared to play a less significant role to improve viral replication in macrophages, but only in the presence of the proper envelope sequences. HIV-1 macrophage tropism thus appears to result from the contribution of several different determinants.

Amino Acid Sequence↗