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PubMed1983

Evidence for a carbanion intermediate in catalysis by spinach ribulose-1,5-bisphosphate carboxylase/oxygenase.

Spinach ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (EC 4.1.1.39) showed marked reactivity towards tetranitromethane in the presence of RuBP, when the enzyme was in the fully activated state. The inactivated enzyme did not catalyze substrate-dependent nitroform production. Nitroform production was proportional to the concentration of the enzyme and tetranitromethane at optimal substrate concentrations. The pH optimum for nitroform production was similar to that for carboxylation. The effects of bicarbonate, ribulose-1,5-bisphosphate, and temperature on partition of the intermediate between production of phosphoglycerate and nitroform indicate that both routes share a common intermediate. Data on stoichiometry of the reaction imply that the intermediate is not oxidized by tetranitromethane but instead is nitrated. The data are compatible with a carbanion intermediate in the reaction catalyzed by ribulose-1,5-bisphosphate carboxylase.

Anions↗

PubMed1989

Identification of an Mr 75000 component of the H+/D-glucose cotransporter from Zea mays with monoclonal antibodies directed against the mammalian Na+/D-glucose cotransporter.

Monoclonal antibodies which interact with the mammalian Na+/D-glucose cotransporter and bind to Mr 75,000 and Mr 47,000 polypeptide components of this transporter have been described (Koepsell, H., Korn, K., Raszeja-Specht, A., Bernotat-Danielowski, S. and Ollig, D. (1988) J. Biol. Chem., 263, 18419-18429). The interaction of these antibodies with plasma membranes from Zea mays L. coleoptiles containing an H+/D-glucose cotransporter was studied. Four monoclonal antibodies cross-reacted with Mr 75,000 and Mr 33,000 polypeptides. One of these antibodies, which inhibits Na+/D-glucose cotransport in the kidney and stimulates Na+/D-glucose cotransport in intestine, stimulates electrogenic uptake of 3-O-methyl-D-[14C]glucose in plant membrane vesicles. The data indicate common epitopes in the mammalian Na+/D-glucose cotransporter and the H+/D-glucose cotransporter of plants and suggest that both transporters contain an Mr 75000 polypeptide component.

3-O-Methylglucose↗

PubMed1988

N-(2-hydroxyethyl)-N-[2-(7-guaninyl)ethyl]amine, the putative major DNA adduct of cyclophosphamide in vitro and in vivo in the rat.

The anti-cancer agent, cyclophosphamide, metabolises to the cytotoxic alkylating agent phosphoramide mustard, which can be dephosphoramidated to give nornitrogen mustard. A rat liver mitochondrial supernatant system was used to study the binding of [chloroethyl 3H]cyclophosphamide to DNA. The reacted DNA was acid-hydrolysed and one major adduct was identified using Sephadex G-10 chromatography, followed by HPLC, using reversed-phase or ion-exchange systems. Further studies, using [14C]guanine as reaction substrate for [chloroethyl 3H]cyclophosphamide, phosphoramide mustard or nornitrogen mustard, demonstrated the main adduct from each reaction had identical chromatographic properties in these systems. The radiolabelled ratio in the [3H]cyclophosphamide-[14C]guanine reaction demonstrated a monoadducted product. From this evidence and from 1H NMR data, the common adduct was putatively identified as a hydroxylated nornitrogen mustard adduct (N-(2-hydroxyethyl)-N-[2-(7-guaninyl)ethyl]amine). In in vivo studies, rats were injected intraperitoneally with 2.775 MBq [3H]cyclophosphamide. Total organ [3H] content and DNA binding levels were ascertained. Maximal levels of [3H] binding to DNA were seen between 1-4 hr with the highest binding levels observed in the bladder. The in vivo adduct was shown, using various HPLC systems, to co-chromatograph with the in vitro adduct and thus the main in vivo adduct was putatively identified as N-(2-hydroxyethyl)-N-[2-(7-guaninyl)ethyl]amine.

Alkylation↗

PubMed1993

SK&F 97426-A a more potent bile acid sequestrant and hypocholesterolaemic agent than cholestyramine in the hamster.

SK&F 97426-A is a novel bile acid sequestrant which was selected for comparison with cholestyramine in vivo because of its superior in vitro bile acid binding properties. The effects of the two sequestrants on faecal bile acid excretion, plasma total cholesterol, VLDL + LDL and HDL cholesterol and triglyceride concentrations and on liver enzymes involved in the synthesis and metabolism of cholesterol were investigated in normocholesterolaemic hamsters. Four studies were conducted to determine the relative potencies of the two resins using a range of doses of the sequestrants over treatment periods of up to 2 weeks. Curves fitted to the resulting data allowed common maximum responses and separate ED50s to be calculated for each sequestrant. The maximum response of both sequestrants was to increase bile acid excretion by 352% and lower plasma total cholesterol by 37-58%. LDL + VLDL and HDL cholesterol were reduced by 56-75% and 25-41%, respectively. SK&F 97426-A was 3 times more potent than cholestyramine at increasing the excretion of bile acids in the faeces and 2.1-3.4-fold and 2.3-3.2-fold more potent at lowering total plasma cholesterol and LDL plus VLDL cholesterol, respectively. In some of the experiments SK&F 97426-A was also more potent than cholestyramine at lowering HDL cholesterol. Plasma triglycerides were also lowered by both sequestrants by up to 31% after 1 week but the relative potency could not be determined. These HDL cholesterol and total triglyceride lowering effects of bile acid sequestrants in the hamster are known not to occur in people treated with cholestyramine. There were minimal differences between hamsters treated for 1 or 2 weeks in the relative potencies or ED50s calculated for the total plasma cholesterol, LDL + VLDL and HDL cholesterol. Both sequestrants may have been slightly more efficacious on these parameters after 2 weeks of treatment. Liver weights were reduced by about 15% by both sequestrants at 2% (w/w) in the diet for 1 week. The activities of the liver HMG-CoA reductase and cholesterol 7 alpha-hydroxylase were increased as expected, whilst the activity of the acyl-CoA:cholesterol acyltransferase was reduced by both sequestrants at this dose. SK&F 97426-A was, therefore, 2-3-fold more potent as a bile acid sequestrant and hypocholesterolaemic agent than cholestyramine when tested in the hamster.

Animals↗

PubMedDate not supplied

Robust alternatives to traditional analysis of variance: Welch W, James J I, James J II, Brown-Forsythe BF.

Contaminated data sets commonly appear in biomedical sciences. Traditional statistical analyses are based on a 'normality' assumption and homogeneity of variances assumption. If either or both assumptions are violated, traditional statistical procedures may give an inflated type I error rate and are then not robust. Robust alternatives to traditional one-way analysis of variance have better power curves and protect against inflated type I error rates.

Analysis of Variance↗

PubMedDate not supplied

Radiation therapy treatment planning using concurrent programming.

Concurrent programming can be applied to the problem of computer graphic simulation of radiation treatment of tumors (radiation treatment planning). Running several tasks or programs simultaneously on behalf of a single user provides a big improvement over the traditional sequential approach, in which editing a treatment plan and computing and displaying dose distributions are separate operations which must be invoked by explicit commands. With our system, the user sees isodose contours being updated automatically and continuously as the plan is edited; this greatly facilitates plan optimization. The complexity of parallel processing has resulted in a 'conventional wisdom' which discourages this technique. The usual approach is to have parallel processes share a common global data structure, which makes interaction hard to control and discourages modularity and data abstraction. We have developed an alternative approach based on message streams which instead enhances modularity and data abstraction while still providing the advantages of parallel processing. The system is very reliable and is used routinely in a practical clinical environment.

Computer Simulation↗

PubMed1991

Identification of peptides within a known protein sequence using COMSEQ analysis of data containing multiple sequences.

Modern methods of automated protein sequence analysis can provide high-quality data with which unambiguous amino-acid sequences can be determined, but analyses are more difficult when the sample is not pure. COMSEQ and auxillary programs were written to facilitate reconciliation of multiple amino-acid sequences potentially contained in noisy data with the known amino-acid sequence of the parent protein. The COMSEQ program prints a matrix in which the first vertical column represents the known amino-acid sequence of a selected protein. Each row of the matrix contains the sequencer yield corresponding to the amino acid in the first column, with each column corresponding to the sequencing reaction cycle. A diagonal which contains net increases of amino acids for each amino acid in the known sequence identifies a peptide potentially contained within the data. The number of matches for each diagonal over the entire known sequence are tabulated and presented as an aid to locating comparisons of greatest interest. The RNDSEQ program conducts multiple analyses using randomized versions of the known amino-acid sequence and tabulates the cumulative frequencies of potential sequence matches irrespective of the true known sequence. TRANSEQ is a utility program that translates edited sequence data from common databases into files that can be used by COMSEQ and RNDSEQ. The programs have been used successfully to identify two co-sequenced peptides from bovine serum albumin, an albumin peptide sequence in the presence of hemoglobin, and to identify two sequences of rat alpha-2u-globulin that differ in their amino termini.

Amino Acid Sequence↗

PubMed1988

Quantifying the carcinogenicity of antineoplastic drugs.

It has been well established that many of the drugs used in cancer therapy are themselves potentially carcinogenic. It is therefore important to quantify the carcinogenic risk associated with specific agents, and to investigate ways of predicting their risk from animal and in vitro studies. In this paper, an index of carcinogenic potency is defined, and applied to published data on acute non-lymphocytic leukemia following therapy with cytotoxic drugs used as single agents. Carcinogenic potency estimates for rats and mice are also obtained for 15 antineoplastic drugs, and the potency correlation between humans and rodents is examined for the five agents for which there are data in common. The broader implications for quantitative cancer risk prediction are discussed.

Animals↗

PubMed1993

Epidemiological transition and geographical discontinuities: the case of cardiovascular mortality in French Polynesia.

The need to maintain the unity of geography justifies the use of every possible approach to the study of spatial discontinuities. The geography of health can be enriched by studying and applying routine methods of regional geography. To achieve this aim, the use of epidemiological transition theory, involving its transposition from the domain of time to space, is proposed. This requires careful analysis of sources of data not commonly used in geography and emphasizes links between health, environment and development. French Polynesia constitutes a prime study area for such an approach, especially because of its multiple contrasts in geographic scale and levels of development between the different archipelagoes and even within individual islands. To demonstrate the utility of this approach, cardiovascular mortality is studied at different geographic scales. Results are displayed as health spatiograms which show the discontinuities of human geography in French Polynesia at different scales. The results appear to constitute synthetic indicators of socio-spatial disparities and permit the geography of health to contribute not only to the measurement of regional health conditions but also to the matters of global human geography.

Cardiovascular Diseases↗

PubMed1983

Regulation of lipogenic enzymes in human diploid fibroblasts by hormones.

The hormonal regulation of two regulatory enzymes of fatty acid synthesis acetyl-CoA carboxylase (EC 6.4.1.2) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49), has been investigated in human diploid fibroblasts. There was a 35% increase in acetyl-CoA carboxylase activity, 72 h following addition of 10 microU/ml insulin to the culture medium. Addition of 1 microgram/ml of 3,3'5-triiodothyronine for 72 h resulted in an increase in acetyl-CoA carboxylase activity to 166% of the controls. The simultaneous addition of 1 microgram/ml triiodothyronine and 10 mU/ml insulin caused the enzyme activity to rise to 240% of the controls. A dose-dependent reduction in acetyl-CoA carboxylase activity was brought about by 1 X 10(-4) to 1 X 10(-3) M dibutyryl cyclic AMP. The earliest effect of dibutyryl cyclic AMP was observed within 24 h. Glucose-6-phosphate dehydrogenase followed qualitatively the same pattern of response, whereas the constitutive enzyme, lactate dehydrogenase (EC 1.1.1.27), did not show significant changes in these experiments. The data demonstrate common features of hormonal regulation of lipogenesis in human fibroblasts with liver and adipose tissue and substantiate the growing evidence that thyroid hormones are of major importance for the regulation of this process.

Acetyl-CoA Carboxylase↗

PubMed1992

Embryotoxicity of 25 psychotropic drugs: a study using CHEST.

Twenty five psychotropic drugs were ranked according to the embryotoxicity dose ranges estimated by the Chick Embryotoxicity Screening Test (CHEST). The chick results were compared with some data for common laboratory mammals. In 17 psychotropic drugs a deleterious dose-dependent effect upon the embryonic cardiovascular system was disclosed, terminating in immediate cardiac arrest.

Animals↗

PubMed1996

The role of inhibition in the hierarchical gating of executed and imagined movements.

A theory is presented concerning the neuronal mechanisms which may underlie the organisation of imagined versus executed movements. A review is first presented of previous theoretical and experimental evidence suggesting that the brain can use the same mechanisms for the imagination and the execution of movement. In particular the fact that adaptation of the vestibulo-ocular reflex can be obtained by pure mental effort and not solely by conflicting visual and vestibular cues has been suggestive of the fact that the brain could internally simulate conflicts and use the same adaptive mechanisms used when actual sensory cues were in conflict. The saccadic system is taken as a good model for the study of this question because the mechanisms which underlie saccade generation are now partially understood at different levels from the brain stem to the cortex. The central idea of the theory is based upon the fact that, in parallel with the excitatory mechanisms underlying saccade generation, several inhibitory mechanisms in cascade allow the selective modulation and blockage of saccades. Synaptic inhibition is therefore supposed to play a major role in a hierarchical selective gating of saccade execution not at one but at several levels allowing a variety of different types of "imagined movements' some involving only the higher levels some in which the execution is only blocked at the very immediate premotor level. But in all cases the theory proposes that imagination and execution have many mechanisms in common. PET data showing that indeed the same structures are activated in both types of movements support this idea although the final answer will have to be brought by neuronal data.

Adaptation, Physiological↗

PubMed1995

Intraoperative hemodilution and autologous platelet rich plasma collection: two techniques for collecting fresh autologous blood.

Intraoperative hemodilution (IH) and autologous platelet rich plasma (APRP) collection are two techniques used to obtain autologous blood in the operating room. They have been used to reduce allogeneic blood exposure in patients undergoing both cardiac and non-cardiac surgery. Both components have the advantage of providing fresh blood not subject to the storage lesion. Whole blood (IH) or platelet rich plasma is removed from the patient as anesthesia is induced and replaced with acellular fluid. The blood is transfused back after bypass or major bleeding has ceased. Although used commonly, the data supporting the use of either technique are controversial. Methodologic problems which have confounded studies evaluating their utility include: poorly defined transfusion criteria, concommitant use of other blood conservation techniques (i.e. cell salvage, pharmacologic agents, hypothermia, controlled hypotension) and changing transfusion practices with greater tolerance of normovolemic anemia. Randomized controlled studies with well defined up to date transfusion criteria are needed to identify patients likely to benefit from these techniques.

Adaptation, Physiological↗

PubMed2004

A transdisciplinary perspective on the links between malaria and agroecosystems in Kenya.

An ecosystem approach was applied to study the links between malaria and agriculture in Mwea Division, Kenya. The study was organized into five phases. Phase I had two components including a stakeholder workshop conducted with community representatives and other key stakeholders, and the collation of data on common diseases from outpatient service records at the local hospital. Phase I aimed at an a priori needs-assessment in order to focus the research agenda. Workshop participants directly contributed to the selection of two villages with rice irrigation and two non-irrigated villages for detailed health studies. In Phase II, various Participatory Rural Appraisal (PRA) tools were used to gather more detailed qualitative information from the study villages. The qualitative results indicated that Mwea residents considered malaria and lack of clean drinking water to be their most important health problems, and this was corroborated by local hospital records. Phase III consisted of a comprehensive household survey developed with inputs from Phases I and II. Phase IV involved a comparative evaluation of entomological and parasitological aspects of malaria in the villages with and without rice irrigation. The malaria parasitological survey found an average Plasmodium falciparum parasite rate of 23.5% among children up to 9 years of age. Results of the entomological evaluation showed a 30-300-fold increase in the number of the local malaria vector, Anopheles arabiensis, in villages with rice irrigation compared to those without irrigation yet malaria prevalence was significantly lower in these villages (0-9% versus 17-54%). The most likely explanation of this 'paddies paradox' in Mwea appeared to be the tendency for A. arabiensis in irrigated villages to feed overwhelmingly on cattle. The results suggested that zooprophylaxis was potentially a practical option for long-term malaria control in the rice irrigated areas, in spite of the large number of A. arabiensis. Phase V consisted of end-of-project workshops for the dissemination of research results and participatory decision-making regarding follow-up actions. Owing to the utilization of a transdisciplinary and participatory approach to research, it was possible to identify opportunities for maintaining zooprophylaxis for malaria in Mwea, through the integration of agroecosystem practices aimed at sustaining livestock systems within a broader strategy for rural development.

Adult↗

PubMed2006

Analysis of microarray experiments of gene expression profiling.

The study of gene expression profiling of cells and tissue has become a major tool for discovery in medicine. Microarray experiments allow description of genome-wide expression changes in health and disease. The results of such experiments are expected to change the methods employed in the diagnosis and prognosis of disease in obstetrics and gynecology. Moreover, an unbiased and systematic study of gene expression profiling should allow the establishment of a new taxonomy of disease for obstetric and gynecologic syndromes. Thus, a new era is emerging in which reproductive processes and disorders could be characterized using molecular tools and fingerprinting. The design, analysis, and interpretation of microarray experiments require specialized knowledge that is not part of the standard curriculum of our discipline. This article describes the types of studies that can be conducted with microarray experiments (class comparison, class prediction, class discovery). We discuss key issues pertaining to experimental design, data preprocessing, and gene selection methods. Common types of data representation are illustrated. Potential pitfalls in the interpretation of microarray experiments, as well as the strengths and limitations of this technology, are highlighted. This article is intended to assist clinicians in appraising the quality of the scientific evidence now reported in the obstetric and gynecologic literature.

Algorithms↗

PubMed2004

The relationships between television viewing in midlife and the development of Alzheimer's disease in a case-control study.

The relationship between leisure activities and development of cognitive impairment in aging has been the subject of recent research. We examined television viewing in association with risk of developing Alzheimer's disease (AD) in a case-control study. Given recent focus on the importance of intellectually stimulating activities as preventive measures against cognitive decline, it is important to examine the effects of less stimulating but common activities. Data are from 135 Alzheimer's disease cases and 331 healthy controls. Demographic characteristics and life history questionnaire responses on the number of hours spent on 26 leisure activities during middle-adulthood (ages 40-59) were analyzed. Logistic regression was used to examine the effects of middle-adulthood leisure activities on case vs. control status. Results indicate that for each additional daily hour of middle-adulthood television viewing the associated risk of AD development, controlling for year of birth, gender, income, and education, increased 1.3 times. Participation in intellectually stimulating activities and social activities reduced the associated risk of developing AD. Findings are consistent with the view that participation in non-intellectually stimulating activities is associated with increased risk of developing AD, and suggest television viewing may be a marker of reduced participation in intellectually stimulating activities.

Adult↗

PubMed2004

Structure and function of radical SAM enzymes.

'Radical SAM' enzymes juxtapose a [4Fe-4S] cluster and S-adenosyl-l-methionine (SAM) to generate catalytic 5'-deoxyadenosyl radicals. The crystal structures of oxygen-independent coproporphyrinogen III oxidase HemN and biotin synthase reveal the positioning of both cofactors with respect to each other and relative to the surrounding protein environment. Each is found in an unprecedented coordination environment including the direct ligation of the [4Fe-4S] cluster by the amino nitrogen and one carboxylate oxygen of the methionine moiety of SAM, as observed for other members of the Radical SAM family by ENDOR. The availability of two protein structures supported by biochemical and biophysical data underscores common features, anticipating the structural elements of other family members. Remaining differences emphasize the plasticity of the protein scaffold in functionally accommodating 600 family members.

Bacterial Proteins↗

PubMed2004

Infective endocarditis: a five-year experience at a tertiary care hospital in Pakistan.

OBJECTIVES: Infective endocarditis is common and data regarding its pattern and outcome from developing countries is sparse. We therefore examined the spectrum, demographics and clinical features of infective endocarditis and sought to determine the factors affecting its clinical outcome. PATIENTS AND METHODS: Over a five-year period at our university hospital in Karachi, Pakistan, we identified 66 patients with infective endocarditis and compared their clinicoepidemiologic features and outcomes to subjects in the West. RESULTS: The male:female ratio was 2:1; overall median age was 24 years (35.5 years for men and 13.5 years for women) (p < 0.001). Median duration of symptoms before presentation was 20.5 days. Major predisposing cardiac abnormalities included congenital (50%) and rheumatic (23%) lesions, and a history of heart surgery (17%). Causative organisms and valvular sites of infection were similar to those seen in developed countries. Blood culture-negative infective endocarditis was found in 48% of cases. Renal failure was more frequent among culture-positive patients (p = 0.055). Risk factors for mortality included neurologic (p = 0.003) and embolic (p = 0.02) complications, renal (p = 0.03) and left ventricular failure (p = 0.002), and a history of cardiac surgery (p = 0.026). Overall mortality was 27%. CONCLUSIONS: Patients with infective endocarditis in Pakistan exhibit significant differences compared to their counterparts in the West, including younger age at presentation, incidence of predisposing cardiac conditions, and gender differences reflecting sociocultural bias. Neurologic and embolic complications, renal failure and heart failure predict a worse outcome.

Adult↗