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Biomedical subjects

J Peters

Publications and source records attributed to J Peters.

At least 163 records · Page 9Linked to original sources
PubMed1999

The kinesin light chain gene: its mapping and exclusion in mouse and human forms of inherited motor neuron degeneration.

The underlying genetic cause is known for only 10-20% of familial motor neuron disease (MND). Thus the genes involved in the aetiology of 80-90% of familial MND remain to be determined, and animal models are powerful tools for undertaking this task. We have mapped a heritable form of motor neuron degeneration in the mouse to a region that has homology to human chromosome 14q32.1-qter. This region contains the kinesin light chain gene (KLC1), which is a candidate for involvement in motor neuron degeneration because of its function in the motor-protein kinesin, and its neuronal expression. To investigate the role of KLC1 in a mouse motor neuron degeneration mutant that we are studying, we have identified mouse Klc1 gene sequences and mapped them with respect to our mutant locus. We have also investigated KLC1 in human patients with familial MND. Based on recombination and the absence of mutations in the coding region of KLC1, this gene can be excluded as a candidate gene in our mouse mutation and, where we have investigated, it is normal in human familial MND.

Animals↗
PubMed1999

Novel molecular architecture of the multimeric archaeal PEP-synthase homologue (MAPS) from Staphylothermus marinus.

The phosphoenolpyruvate (PEP)-synthases belong to the family of structurally and functionally related PEP-utilizing enzymes. The only archaeal member of this family characterized thus far is the Multimeric Archaeal PEP-Synthase homologue from Staphylothermus marinus (MAPS). This protein complex differs from the bacterial and eukaryotic representatives characterized to date in its homomultimeric, as opposed to dimeric or tetrameric, structure. We have probed the molecular architecture of MAPS using limited proteolytic digestion in conjunction with electron microscopic, biochemical, and biophysical techniques. The 2.2 MDa particle was found to be organized in a concentric fashion. The 93.7 kDa monomers possess a pronounced tripartite domain structure and are arranged such that the N-terminal domains form an outer shell, the intermediate domains form an inner shell, and the C-terminal domains form a core structure responsible for the assembly into a multimeric complex. The core domain was shown to be capable of assembling into the native multimer by recombinant expression in Escherichia coli. Deletion mutants as well as a synthetic peptide were investigated for their state of oligomerization using native polyacrylamide gel electrophoresis, molecular sieve chromatography, analytical ultracentrifugation, circular dichroism (CD) spectroscopy, and chemical cross-linking. Our data confirmed the existence of a short C-terminal, alpha-helical oligomerization motif that had been suggested by multiple sequence alignments and secondary structure predictions. We propose that this motif bundles the monomers into six groups of four. An additional formation of 12 dimers between globular domains from different bundles leads to the multimeric assembly. According to our model, each of the six bundles of globular domains is positioned at the corners of an imaginary octahedron, and the helical C-terminal segments are oriented towards the centre of the particle. The edges of the octahedron represent the dimeric contacts. Phylogenetic analysis suggests that the ancient predecessor of this family of enzymes contained the C-terminal oligomerization motif as a feature that was preserved in some hyperthermophiles.

Amino Acid Sequence↗
PubMed1999

Structure of VAT, a CDC48/p97 ATPase homologue from the archaeon Thermoplasma acidophilum as studied by electron tomography.

Valosine-containing protein-like ATPase from Thermoplasma acidophilum is a member of the superfamily of ATPases associated with a diversity of cellular activities and is closely related to CDC48 from yeast and p97 from higher eukaryotes and more distantly to N-ethylmaleimide-sensitive fusion protein. We have used electron tomography to obtain low-resolution (2-2.5 nm) three-dimensional maps of both the whole 500 kDa complex and the N-terminally truncated valosine-containing protein-like ATPase from T. acidophilum complex lacking the putative substrate binding domain.

Adenosine Triphosphatases↗
PubMed1999

A cluster of oppositely imprinted transcripts at the Gnas locus in the distal imprinting region of mouse chromosome 2.

Imprinted genes tend to occur in clusters. We have identified a cluster in distal mouse chromosome (Chr) 2, known from early genetic studies to contain both maternally and paternally imprinted, but unspecified, genes. Subsequently, one was identified as Gnas, which encodes a G protein alpha subunit, and there is clinical and biochemical evidence that the human homologue GNAS1, mutated in patients with Albright hereditary osteodystrophy, is also imprinted. We have used representational difference analysis, based on parent-of-origin methylation differences, to isolate candidate imprinted genes in distal Chr 2 and found two oppositely imprinted genes, Gnasxl and Nesp. Gnasxl determines a variant G protein alpha subunit associated with the trans-Golgi network and Nesp encodes a secreted protein of neuroendocrine tissues. Gnasxl is maternally methylated in genomic DNA and encodes a paternal-specific transcript, whereas Nesp is paternally methylated with maternal-specific expression. Their reciprocal imprinting may offer insight into the distal Chr 2 imprinting phenotypes. Remarkably, Gnasxl, Nesp, and Gnas are all part of the same transcription unit; transcripts for Gnasxl and Nesp are alternatively spliced onto exon 2 of Gnas. This demonstrates an imprinting mechanism in which two oppositely imprinted genes share the same downstream exons.

Alternative Splicing↗
PubMed1999

Blood pressure reduction and diabetes insipidus in transgenic rats deficient in brain angiotensinogen.

Angiotensin produced systemically or locally in tissues such as the brain plays an important role in the regulation of blood pressure and in the development of hypertension. We have established transgenic rats [TGR(ASrAOGEN)] expressing an antisense RNA against angiotensinogen mRNA specifically in the brain. In these animals, the brain angiotensinogen level is reduced by more than 90% and the drinking response to intracerebroventricular renin infusions is decreased markedly compared with control rats. Blood pressure of transgenic rats is lowered by 8 mmHg (1 mmHg = 133 Pa) compared with control rats. Crossbreeding of TGR(ASrAOGEN) with a hypertensive transgenic rat strain exhibiting elevated angiotensin II levels in tissues results in a marked attenuation of the hypertensive phenotype. Moreover, TGR(ASrAOGEN) exhibit a diabetes insipidus-like syndrome producing an increased amount of urine with decreased osmolarity. The observed reduction in plasma vasopressin by 35% may mediate these phenotypes of TGR(ASrAOGEN). This new animal model presenting long-term and tissue-specific down-regulation of angiotensinogen corroborates the functional significance of local angiotensin production in the brain for the central regulation of blood pressure and for the pathogenesis of hypertension.

Angiotensin II↗
PubMed1999

An alternative transcript of the rat renin gene can result in a truncated prorenin that is transported into adrenal mitochondria.

Characterization of the local renin-angiotensin system in the rat adrenal zona glomerulosa indicated a dual targeting of renin both to the secretory pathway and mitochondria. To investigate the transport of renin into mitochondria, we constructed a series of amino-terminal deletion variants of preprorenin. One of these variants, lacking the complete signal sequence for the endoplasmic reticulum and 10 amino acids of the profragment, was transported efficiently into isolated mitochondria. The transport was further shown to be dependent on mitochondrial membrane potential and ATP synthesis. Analysis of adrenal RNA revealed the existence of 2 renin transcripts. While one of the transcripts corresponds to the known full-length transcript, the other one lacks exon 1; instead, exon 2 is preceded by a domain of 80 nucleotides originating from intron 1. This domain, as well as the following region of intron 1 being excised, shows all essential sequence elements defining an additional, so-far-unknown exon. The second mRNA possibly derives from an additional transcription start in intron 1 and an alternative splicing process. Translation of this mRNA could result in a truncated prorenin representing a cytosolic form of renin, which is required for transport into mitochondria. This truncated prorenin corresponds exactly to the deletion variant being imported into mitochondria in vitro.

Adrenal Glands↗
PubMed1999

Glial cell swelling--effect of hypothermia.

The effect of mild to moderate hypothermia (32/27 degrees C) was analyzed on the cell volume of C6 glioma cells and primary cultured astrocytes at normal pH, during lactacidosis (pH6.2) and during exposure to glutamate or arachidonic acid in vitro. The cells were suspended in an incubation chamber under continuous control of pH, pO2 and temperature. Cell swelling was quantified by an advanced Coulter-system. Following a control period at 37 degrees C, the ambient temperature was decreased to 27 and 32 degrees C for 30 min. Hypothermia alone led to an immediate and significant cell volume increase of 107.3 +/- 0.4% (mean +/- SEM) of control after 30 min at 32 degrees C. Yet, hypothermia (27 degrees C) afforded partial protection against the acidosis-induced cell swelling at pH 6.2, attaining 120.4 +/- 0.9% in the normothermic control group after 60 min, while only 111.3 +/- 0.9% at 27 degrees C. Hypothermia, however, was not associated with a reduction of the glutamate- or arachidonic acid-induced cell swelling. The results demonstrate that mild hypothermia per se induces glial cell swelling, but simultaneously inhibits cell swelling from acidosis, while not from glutamate- or arachidonic acid.

Acidosis, Lactic↗
PubMed1999

T lymphocytes and altered keratinocytes express interferon-gamma and interleukin 6 in lichen planus.

Lichen planus is assumed to represent a delayed hypersensitivity reaction, in the course of which cytokines control the proliferation and differentiation of cytotoxic T lymphocytes which attack the epidermis and cause apoptosis of undifferentiated keratinocytes. Since interferon-gamma and interleukin 6 are known to be markedly generated in lichen planus, we investigated the cellular localization of these cytokines in affected skin/oral mucosa biopsy specimens using in situ hybridization for interferon-gamma and in situ reverse transcription-polymerase chain reaction for interleukin 6 mRNA. In the upper subepithelial connective tissue interferon-gamma mRNA was noted within proliferating CD3+ T lymphocytes. In this tissue compartment interleukin 6 mRNA was detected in infiltrating CD4+ and CD8+ T lymphocytes. In the epithelium, expression of interferon-gamma mRNA and interleukin 6 mRNA was observed in the basal and suprabasal keratinocytes of altered skin/oral mucosa. In contrast, normal skin did not reveal any interferon-gamma or interleukin 6 expression, although a few CD4+ and CD8+ T lymphocytes were noted in the dermis as well as the epidermis. These findings indicate that in lichen planus the proinflammatory cytokines interferon-gamma and interleukin 6 are produced not only by activated T lymphocytes but also by altered keratinocytes, and suggest that stimulated keratinocytes may amplify the course of lichen planus.

Biopsy↗
PubMed1999

The views of nurses to the conduct of a randomised controlled trial of problem drinkers in an accident and emergency department.

The Trent Regional Health Authority funded a study in 1995 to train nurses in an accident and emergency (A&E) department to screen all adult attendees for alcohol problems with a view to identifying a sample of problem drinkers to participate in a randomised controlled trial (RCT). In the RCT identified drinkers were to be assigned either to health education plus brief counselling intervention or, as controls, to health education alone. Despite 16654 attendance's at A&E during the recruitment phase of the study only 20% of attendees were screened of whom a further 19% were identified as problem drinkers by the CAGE screening questionnaire. Less than half of the problem drinkers were, however, provided with feedback by the nurses, leaving a small group of 264 eligible for entry to the RCT. The great majority of this subgroup refused an initial appointment at the specialist clinic and so the trial was abandoned. A number of in-depth interviews were undertaken with the nurses in an attempt to understand ways in which the overall conduct of the study might have been improved. This paper outlines in some detail some of the reasons for the lack of success with the study which include; general environmental factors that undoubtedly led to stress and poor morale amongst the nursing team, the differences in perception between managers and clinical nurses concerning the value of research and the inadequacy of the initial training programme. The paper concludes that there are problems in the NHS which do not provide a helpful backcloth to the successful conduct of health services research.

Adult↗
PubMed1999

Assessment of ambulance response performance using a geographic information system.

The accessibility, distribution and utilisation of emergency medical services are important components of health care delivery. The impact of these services on well-being is heightened by the fact that ambulance resources must respond in a reliable and timely manner to emergency calls from demand areas. However, many factors, such as the unavailability of an ambulance at a center closest to a call, can adversely influence response time. This paper discusses the design and implementation of a framework developed in a Geographic Information System for assessing ambulance response performance. A case study of ambulance response in three communities in Southern Ontario, Canada is presented that allows easy and rapid identification of anomalous calls that may adversely affect overall operating performance evaluation. Extensions of the framework into a fully fledged service deployment and planning decision support system are discussed.

Ambulances↗
PubMed1999

The gene mutated in bare patches and striated mice encodes a novel 3beta-hydroxysteroid dehydrogenase.

X-linked dominant disorders that are exclusively lethal prenatally in hemizygous males have been described in human and mouse. None of the genes responsible has been isolated in either species. The bare patches (Bpa) and striated (Str) mouse mutations were originally identified in female offspring of X-irradiated males. Subsequently, additional independent alleles were described. We have previously mapped these X-linked dominant, male-lethal mutations to an overlapping region of 600 kb that is homologous to human Xq28 (ref. 4) and identified several candidate genes in this interval. Here we report mutations in one of these genes, Nsdhl, encoding an NAD(P)H steroid dehydrogenase-like protein, in two independent Bpa and three independent Str alleles. Quantitative analysis of sterols from tissues of affected Bpa mice support a role for Nsdhl in cholesterol biosynthesis. Our results demonstrate that Bpa and Str are allelic mutations and identify the first mammalian locus associated with an X-linked dominant, male-lethal phenotype. They also expand the spectrum of phenotypes associated with abnormalities of cholesterol metabolism.

3-Hydroxysteroid Dehydrogenases↗
PubMed1999

Hepatic encephalopathy--a physostigmine-reactive central anticholinergic syndrome?

This report describes an association between hepatic encephalopathy and central anticholinergic syndrome (CAS). A 60-year-old anaemic woman was admitted unconscious and with a delayed reaction to pain but with no focal neurological deficits. She had signs of portal hypertension and a history of non-alcoholic liver cirrhosis grade Child B. Suspecting upper gastro-intestinal bleeding, she was intubated for gastro-duodenoscopy and a fibrin-covered ulcer was revealed. Raised intra-abdominal pressure resulting from ascites caused cardiopulmonary failure, which required mechanical ventilation for 24 h, but extubation was possible after drainage of the ascites and blood volume replacement therapy. However, her neurological state remained unchanged despite normal blood ammonia concentration and no sedation. CAS was considered and physostigmine injected with immediate effect. The patient opened her eyes immediately and was fully orientated to personal and medical history. We suggest that hepatic encephalopathy may trigger CAS, although the significance of physostigmine in the treatment of hepatic encephalopathy remains to be addressed by controlled investigations.

Central Nervous System Diseases↗
PubMed1999

Botulism with respiratory insufficiency requiring extra corporeal carbon dioxide removal.

Despite a low incidence of botulism in the industrialized world some cases occasionally occur in Germany after eating contaminated food. Because botulism is rarely seen, most physicians are unfamiliar with its early recognition and treatment. However, immediate intensive care treatment is important. We report the case of a previously healthy 54-year-old female who developed signs of botulism after eating vacuum packed smoked fish and developed severe respiratory insufficiency with difficult carbon dioxide elimination in the days following.

Botulism↗
PubMed1999

[Mechanisms of tachyphylaxis in regional anesthesia of long duration].

Tachyphylaxis to local anesthetics is defined as a decrease in duration, segmental spread or intensity of a regional block despite repeated constant dosages. However, there is disagreement about the incidence of tachyphylaxis. In contrast to tachyphylaxis, pseudotachyphylaxis denotes time dependent variations in pain or circadian changes in the duration of local anesthetic action. Tachyphylaxis appears neither to be linked to structural or pharmacological properties of the local anesthetics nor to the technique or mode of their administration. The mechanisms underlying tachyphylaxis are open to debate and include changes in pharmacokinetics or pharmacodynamics. Considering pharmacokinetics, local edema, an increased epidural protein concentration, changes in local anesthetic distribution in the epidural space or a decrease of perineural pH could result in decreased diffusion of the local anesthetics from the epidural space to their binding sites at the sodium channel. Increased clearance of local anesthetics from the epidural space may be caused both by increased epidural blood flow or increased local metabolism. Considering pharmacodynamics, antagonistic effects of nucleotides or increased sodium concentration, increased afferent input from nociceptors or receptor down regulation of the sodium channels have been implicated. However, none of these theoretical considerations is supported strongly enough by data to explain tachyphylaxis. A new possibility to maintain for a longer time neural blockade is the design of new ultralong-acting local anesthetics. Liposomal formulations of local anesthetics also appear suitable to provide longer lasting regional anesthesia. The recent observation that NMDA-antagonists as well as NO-synthase-inhibitors prevent the development of tachyphylaxis suggests involvement of the nitric oxide pathway in the development of tachyphylaxis. Accordingly, NMDA-antagonists or NO-synthase-inhibitors may prevent tachyphylaxis.

Anesthesia, Conduction↗