Biomedical subjects

A Davies

Publications and source records attributed to A Davies.

At least 181 records · Page 10Linked to original sources

PubMed1993

Membrane defence against complement lysis: the structure and biological properties of CD59.

The complement system is an important branch of the innate immune response, constituting a first line of defence against invading microorganisms which activate complement via both antibody-dependent and -independent mechanisms. Activation of complement leads to (a) a direct attack upon the activating cell surface by assembly of the pore-forming membrane attack complex (MAC), and (b) the generation of inflammatory mediators which target and recruit other branches of the immune system. However, uncontrolled complement activation can lead to widespread tissue damage in the host, since certain of the activation products, notably the fragment C3b and the C5b-7 complex, can bind nonspecifically to any nearby cell membranes. Therefore it is important that complement activation is tightly regulated. Our own cells express a number of membrane-bound control proteins which limit complement activation at the cell surface and prevent accidental complement-mediated damage. These include decay-accelerating factor, complement receptor 1 and membrane cofactor protein, all of which are active at the level of C3/C5 convertase formation. Until recently, cell surface control of MAC assembly had been attributed to a single 65-kD membrane protein called homologous restriction factor (alternatively named C8-binding protein and MAC-inhibiting protein). However a second MAC-inhibiting protein has since been discovered and it is now clear that this protein plays a major role in the control of membrane attack. This review charts the rapid progress made in elucidating the protein and gene structure, and the mechanism of action of this most recently discovered complement inhibitor, CD59.

Animals↗

PubMed1993

Reversal of diabetic related accelerated fetal growth by maternal glycaemic control.

In a young woman with insulin-dependent diabetes mellitus, poor diabetic control during the second trimester of pregnancy resulted in ketoacidosis, accelerated fetal growth and polyhydramnios. With the establishment of tight maternal glycaemic control, both accelerated intrauterine growth and polyhydramnios were reversed and a good pregnancy outcome resulted.

Adult↗

PubMed1993

Comparative analysis of phosphotyrosyl polypeptides in normal and leukemic human T lymphocytes activated via CD3 or CD2.

Phosphotyrosyl polypeptides induced following CD3- or CD2- specific antibody stimulation were analysed in different human T cell lines by immunoblotting or by immunoprecipitation of 32P-labelled cell lysates using a phosphotyrosine-specific monoclonal antibody. In Jurkat cells, resting peripheral T lymphocytes, T lymphoblasts, CD8+ T lymphoblasts and a CD4+ T cell clone, CD3 stimulation induced a strong but transient tyrosine phosphorylation of at least 15 polypeptides. However, in peripheral T cells and T blasts, the kinetics of phosphorylation were considerably slower than in Jurkat cells. The pattern of phosphotyrosyl polypeptides induced by CD3 stimulation was similar, although some differences were noted between normal T cells and Jurkat, especially at the level of the extent of phosphorylation. As had been previously reported for Jurkat T cells, a qualitatively similar tyrosine phosphorylation response was induced upon CD2 or CD3 stimulation in each of the analysed T cell populations, suggesting that CD3 and CD2 share a common pathway of protein tyrosine kinase (PTK) activation. In HPB. ALL leukemia T cells (which express very low levels of CD45), both CD3 and CD2 stimulation induced only very weak protein tyrosyl phosphorylation. However, a 50 kDa polypeptide, which was part of an inducible doublet in Jurkat or normal T lymphocytes, was constitutively tyrosyl-phosphorylated in the HPB. ALL line. These results suggest that there is a common pathway of early PTK activation following CD3- or CD2-mediated stimulation in mature T cells, whether they express surface CD4 or CD8, and also that the PTK may be differently regulated in different T cell populations leading to different kinetics or intensity of tyrosyl phosphorylation.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1993

Histological evaluation of the effect of 0.05% tretinoin in the treatment of photo damaged skin. Geographic differences in elastosis in baseline biopsies.

In a randomised double-blind vehicle controlled trial of 0.05% tretinoin cream in the treatment of photodamaged skin, the histological results of paired biopsies from 28 individuals who applied tretinoin for 26 weeks are compared with 28 paired biopsies from a control group applying vehicle alone. There was a significant increase in epidermal thickness in the tretinoin-treated group (P < .001). Epidermal atrophy was reversed in ten patients applying tretinoin cream. Baseline biopsies obtained from participants in Melbourne, Victoria (38 degrees latitude) showed significantly less elastosis than those in Sydney (34 degrees latitude) and Newcastle in N.S.W., although the two groups did not show significant differences in age or sex, and the differences could not be correlated with skin type. Tretinoin cream had no effect on the degree of solar elastosis after 26 weeks application. Tretinoin cream appears effective in reversing epidermal atrophy and clinically diminishes fine wrinkling, mottled hyperpigmentation and skin roughness. Tretinoin cream may not offer a solution to the gross solar damage seen in the Australian population who have marked solar elastosis as a principal, clinical and histologic finding. However it is possible that dermal repair and reversal of solar elastosis may require topical application of tretinoin cream for a longer period than the six months used in this trial.

Administration, Topical↗

PubMed1993

A comparison of the mechanogram of the ankle jerk in men and women: observations using an adjustable dorsiflexing torque, high inertia mechanical filter and automatic readout system.

An instrument of new design has been constructed to measure the contractions of the calf musculature resulting from a tap on the Achilles tendon. The instrument provides a predetermined and adjustable dorsiflexing torque from a printed motor, but the contractions are virtually isometric as the system is one of high inertia. Peak force, half-contraction time and half-relaxation time are monitored by electronic circuits equipped with digital output meters. Observations have been made on fifty-two male and forty-five female medical students. There were no significant differences in the peak torques generated by the contractions between the men and women students and no difference in the half-contraction times. The half-relaxation times of the women were, however, significantly longer than those of the men (P = 0.0001). In another group of students the EMG discharges following a tendon tap were recorded, there was no significant difference in the duration of the activity in men and women. Observations have also been made on twenty-three male and seventy female subjects whose mean ages were in the mid-sixties. The peak torques generated by the contractions were significantly higher in the women (P = 0.03). There was no difference in the half-contraction times, but the half-relaxation times of the women were significantly longer (P = 0.001). Possible reasons for the differences are discussed.

Adolescent↗

PubMed1993

A survey of basic resuscitation knowledge among resident paediatricians.

A telephone questionnaire was undertaken to evaluate the knowledge of resident paediatricians on the subject of the basic resuscitation of the acutely sick child. The questionnaire was targeted at 88 resident paediatricians in hospitals accepting paediatric emergencies in four health regions. Outcome was measured as a correct response to questions based on several emergency scenarios and on the confidence expressed of basic resuscitation knowledge. The subject of emergency management of the child with a compromised upper airway was poorly answered with 40/73 (55%) resident paediatricians suggesting an incorrect endotracheal tube size for an 8 year old child. Fluid management was also deemed unsatisfactory with only 36/73 (49%) providing adequate transfusion secondary to haemorrhagic shock. In addition only 19/73 (26%) mentioned the intraosseous route as a means of obtaining vascular access in a child in extremis. Confidence of the knowledge of basic resuscitation of children was low among resident paediatricians with only 30/73 (41%) expressing confidence and 69/73 (94%) expressing a desire for more formal training in paediatric resuscitation. Resident paediatricians are usually the key personnel in the management of very sick children. This survey demonstrates a low level of basic resuscitation knowledge among resident paediatricians of all grades that must be remedied at a local and national level.

Cardiopulmonary Resuscitation↗

PubMed1993

von Willebrand factor, the endothelium and obesity.

von Willebrand factor (vWf), risk factors for atherosclerosis, body mass index (BMI) and waist-to-hip ratio (WHR) were measured in 108 non-diabetic patients attending lipid and vascular disease clinics and in 107 normal asymptomatic controls. High levels of vWf and increased BMI relative to controls were found in patients with hyperlipidaemia and vascular disease, but WHR was higher only in patients with vascular disease. Total serum cholesterol concentration (P < 0.001), systolic blood pressure (P < 0.001), smoking (P < 0.02) and BMI (P < 0.001), but not WHR, were associated with vWf. As raised levels of vWf are a probable indicator of endothelial damage in vascular disease, these data suggest that obesity has an adverse influence on the endothelium and may help explain its link with cardiovascular disease.

Adult↗

PubMed1992

Mammalian nitrobenzylthioinosine-sensitive nucleoside transport proteins. Immunological evidence that transporters differing in size and inhibitor specificity share sequence homology.

Polyclonal antibodies were raised against the nitrobenzylthioinosine (NBMPR)-sensitive nucleoside transporter of human erythrocyte membranes. On Western blots of these membranes they labeled the broad "band 4.5" region (average apparent M(r) 55,000), which contains both the nucleoside and glucose transport proteins. However, they did not recognize the glucose transporter when this was prepared free of nucleoside transporter by expression from a cDNA clone. Their specificity for the nucleoside transporter was confirmed by the ability to immunoadsorb NBMPR- but not cytochalasin B-binding sites from a detergent-solubilized mixture of band 4.5 proteins. Although a large proportion of the antibodies recognized extracellular epitopes, these appeared to be located primarily on the polypeptide moiety of the glycoprotein, as demonstrated by the ability of the antibodies strongly to label the deglycosylated transporter (apparent M(r) 45,000) on Western blots. The antibodies were species-cross-reactive, recognizing nucleoside transporters from pig and rabbit erythrocytes and from rat liver. The pig protein is similar to the human transporter in its inhibitor sensitivity but is considerably larger (apparent M(r) 57,000 after deglycosylation). In contrast, the rat protein is similar in size to the human transporter (apparent M(r) 45,000 after deglycosylation) but much less sensitive to the inhibitors dilazep and dipyridamole. These findings indicate that despite their differences in size and inhibitor specificity, the NBMPR-sensitive nucleoside transporters of these mammalian species are related in amino acid sequence.

Affinity Labels↗

PubMed1992

Acute lesions in rats caused by 3-amino-1,2,4-benzotriazine-1,4-dioxide (SR 4233) or nitromin: a comparison with rates of reduction in microsomal systems from target organs.

Pathological lesions to male Fischer rats were investigated 24 h after the administration of 3-amino-1,2,4-benzotriazine-1,4- dioxide (SR 4233) or nitromin, two compounds which need to undergo bioreductive activation in order to exert their toxic effects. Although SR 4233 reduction leads to a putative free radical species while with nitromin a bifunctional alkylating agent is formed, in both instances, the bone marrow was a major target organ. However, the response of other organs to these compounds differed. SR 4233 caused lesions to the olfactory epithelium, liver, kidney and thymus. Nitromin caused focal haemorrhages on the intestine, which were reduced in germ-free rats. Rates of reduction of SR 4233 or nitromin were determined under anaerobic conditions using microsomal preparations from target tissues. With SR 4233 as a substrate, reductase activities were highest in the olfactory epithelium, 6 fold higher than in the liver. SR 4233 reductase activities generally correlated with those of NADPH:cytochrome c reductase or the concentration of cytochrome P-450 reductase protein in the affected organs while with nitromin, there appeared to be no such relationship. The present results support the concept that the expression of pathological damage in vivo is a multifactorial process and does not directly correlate with initial rates of reduction of either drug determined in vitro.

Animals↗

PubMed1992

Use of family history in a screening clinic for familial ovarian cancer.

We have estimated the risks of ovarian and other types of cancer in first-degree relatives of women who have developed the disease (the index patients). The number of deaths from each type of cancer was determined from pedigrees taken from 391 self-referred, asymptomatic women attending a screening clinic for familial ovarian cancer. These values were compared with the expected number of deaths for women in the general population (calculated from life tables), and the relative risks were used to estimate lifetime risks. The overall relative risk were 4.5, 1.4, 1.3, and 1.1 for ovarian, stomach, breast, and endometrial cancers, respectively. The risks were invariably higher if the index patient was < 55 years old. Ovarian cancer appeared to have no clear inheritance pattern in 290 pedigrees and there was no increased risk for the first-degree relatives. Eighty-two pedigrees were compatible with a diagnosis of a multiple-site cancer family syndrome and the relative risks were 6.1, 2.8, 3.7, and 2.7 for ovarian, breast, stomach, and colorectal cancer, respectively. There was evidence of site-specific ovarian cancer in 19 families; the relative risk for the first-degree relatives was 39.1 and the lifetime risk 1 in 2. We believe that family history can be used to identify women who are at a high risk of developing ovarian and certain other types of cancer. This information can be used to counsel women attending ovarian cancer screening clinics and to maximize the usefulness of current resources.

Female↗

PubMed1992

Rapists' behaviour: a three aspect model as a basis for analysis and the identification of serial crime.

In this paper it is proposed that the behaviour of an offender during a sexual assault can be considered as consisting of three main groupings or 'aspects'. These have been termed 'Modus Operandi', 'Sexual and Personal Gratification' and 'Attitude and Intimacy'. Although an oversimplification, such a model facilitates a preliminary description of the offender which can be of direct assistance to an investigating officer. Various factors affect the consistency and variability of behaviour and the model has formed a basis for the development of a concept as to which behaviours might be the more useful for identifying linked offences. This more systematic approach to the investigative and intelligence processes is reliant on a victim's statement containing very detailed information about the offender's actions, together with a record of as much of his speech as can be recollected. The material required is described using the model and the text is illustrated with case examples. Instances are quoted of the possible inferences and their relevance to the investigation of sexual offences.

Criminal Psychology↗

PubMed1992

Analysis of the glucose transporter content of islet cell lines: implications for glucose-stimulated insulin release.

Glucose transport across the plasma membrane of mammalian cells is mediated by a family of homologous proteins. Each glucose transporter isoform has a specific tissue distribution which relates to that tissue's demand for glucose. The beta-cells of pancreatic islets are known to express a distinct glucose transporter isoform, termed GLUT 2, which has a high Km for glucose. In this study, we examined the glucose transporter content of normal rat islets and three beta cell lines, beta-TC, HIT and RIN cells. We show that at the protein level, GLUT 2 is the only detectable transporter isoform in normal islets, and that all three cell lines also express detectable GLUT 2. In contrast, all three cell lines expressed high levels of GLUT 1, but this isoform was not detected in normal islets. Neither the native islets nor any of the cell lines expressed GLUT 3. The insulin-responsive glucose transporter GLUT 4 was detected at very low levels in beta-TC cells; to our knowledge, this is the only non-muscle or adipose cell line which expresses this isoform. We propose that the elevated level of GLUT 1 expression, together with a reduced expression of the high Km transporter GLUT 2, may account for the characteristic aberrant patterns of glucose-stimulated insulin release in cell lines derived from beta-cells.

Amino Acid Sequence↗

PubMed1992

Fusobacterium nucleatum bacteraemia with multiple liver abscesses in an HIV-I antibody positive man with IgG2 deficiency.

Liver abscess formation due to Fusobacterium nucleatum is rare. We describe an HIV-I antibody positive man, with normal surrogate markers of cell-mediated immunity, who presented with F. nucleatum bacteraemia and liver abscess formation. He was found to have IgG2 subclass deficiency. This case illustrates the clinical importance of altered B-cell function in patients who are at an early stage of HIV disease.

Adult↗

PubMed1992

The effect of high-frequency ventilation on non-Newtonian properties of bronchial mucus.

We have investigated the changes in the non-Newtonian properties of human bronchial mucus brought about by in vitro high frequency ventilation. This type of ventilation brought about changes in viscous properties, measured during creep and oscillation of the mucus, which would be expected to reduce mucus clearance in vivo. We suggest that any beneficial effects of clinical high-frequency ventilation on respiratory mucus clearance in patients are not brought about by long-term (more than a few seconds) changes in the viscous properties of the mucus itself.

Elasticity↗

PubMed1992

Genotoxic potential of tamoxifen and analogues in female Fischer F344/n rats, DBA/2 and C57BL/6 mice and in human MCL-5 cells.

Chronic administration of tamoxifen to female rats causes hepatocellular carcinomas. We have investigated damage to liver DNA caused by the administration of tamoxifen to female Fischer F344/N rats or C57B1/6 or DBA/2 mice using 32P-postlabelling. Following the administration of tamoxifen for 7 days (45 mg/kg/day) and extraction of hepatic DNA, up to 7 radiolabelled adduct spots could be detected after PEI-cellulose chromatography of the 32P-labelled DNA digests. Tamoxifen caused a time-dependent increase in the level of adduct detected up to a value of at least 1 adduct/10(6) nucleotides after 7 days dosing. A dose response relationship was demonstrated over the range of 5-45 mg/kg/day (0.013-0.12 mmol/kg/day). On cessation of dosing there was a loss of adducts from the liver DNA. These adducts were not detected in DNA from vehicle-dosed controls or in DNA from kidney, lung, spleen, uterus or peripheral lymphocytes. Pyrrolidinotamoxifen caused a similar level of adduct formation as tamoxifen. In contrast, no significant adduct formation could be detected in liver DNA from rats given droloxifene or toremifene. Mice given tamoxifen (45 mg/kg/day for 4 days) showed levels of adducts in the liver which were 30-40% of those present in rats. Exposure of rat hepatocytes to tamoxifen in vitro, resulted in induction of unscheduled DNA synthesis, when preparations from rats which had been pretreated with tamoxifen in vivo were used. No such increase could be detected in hepatocytes from control rats, suggesting tamoxifen may induce enzymes responsible for its own activation. Tamoxifen induced a significant increase in micronucleus formation in a dose dependent manner in cultures of MCL-5 cells, a human cell line that expresses 5 different human cytochrome P450 isoenzymes, as well as epoxide hydrolase.

Animals↗

PubMed1992

Rat bite fever without the bite.

The case is reported of a patient who developed an acute arthropathy, which was initially diagnosed as acute septic arthritis. The true diagnosis of rat bite fever due to Streptobacillus moniliformis was delayed because of difficulty in growing the organism, which has fastidious growth requirements. The patient had no history of rat bite, which is the usual form of transmission of this disease.

Arthritis, Infectious↗

PubMed1992

Management of gastroenteritis in early childhood.

The most important aspect of modern management of acute diarrhoeal illness in children is that of oral rehydration therapy, and drug therapy is very rarely indicated. Despite the dramatic decline in mortality and morbidity in recent years, there is still the need for continuing education in the appropriate use of oral rehydration solutions. The constitution of oral rehydration solutions and policies of feeding practices during illness continue to be controversial, mainly because of wide variation in the aetiology of the diarrhoea, the nutrition of the child, and the economic and public health factors involved in any particular community. The priority of all healthcare workers is to provide simple guidelines in the use of a safe oral rehydration solution while discouraging unsafe treatments.

Anti-Bacterial Agents↗

PubMed1992

Membrane attack complex (MAC)-mediated damage to spermatozoa: protection of the cells by the presence on their membranes of MAC inhibitory proteins.

Although antibody and complement are known to cause immobilization and killing of spermatozoa in vitro the components of the complement system mediating these effects remain undefined. Here we have examined the effects of the membrane attack complex (MAC) on spermatozoa and demonstrate that spermatotoxic effects are dependent on assembly of the complete MAC. We subsequently examined the presence and functional significance of the complement regulatory proteins decay accelerating factor (DAF), MAC-inhibiting protein (MIP) and CD59 antigen on spermatozoa. Both DAF and CD59 antigen were present on the membranes of these cells. Neutralization of CD59 antigen with specific antibodies increased the susceptibility of the cells to MAC-mediated damage, suggesting a role for this molecule in the protection of spermatozoa from complement-mediated damage in the female reproductive tract.

Antigens, CD↗