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Biomedical subjects

K Baker

Publications and source records attributed to K Baker.

At least 73 records · Page 4Linked to original sources
PubMed1995

Enzymatic synthesis and purification of uridine diphosphate [14C]galacturonic acid: a substrate for pectin biosynthesis.

Pectins are complex polysaccharides that contain 1,4-linked alpha-D-galactosyluronic acid residues found in the primary wall of all higher plant cells. The pectic polysaccharides play critical roles in cell wall structure and in plant growth and development. As a first step in studying pectin biosynthesis a method was developed to routinely generate and purify UDP-[U-14C]galacturonic acid (UDP-[14C]GalA), the nucleotide sugar substrate for homogalacturonan biosynthesis. UDP-[14C]GalA was enzymatically synthesized by 4-epimerization of commercially available UDP-[U-14C]glucuronic acid (UDP-[14C]GlcA) using a particulate preparation from radish roots. The resulting mixture of UDP-[14C]GalA and UDP-[14C]GlcA was separated by high-performance anion-exchange chromatography using a Dionex CarboPac PA1 anion-exchange column. The UDP-sugars were detected by their absorbance at 262 nm or by pulsed amperometric detection following postcolumn addition of NaOH. The yield of UDP-[14C]GalA obtained using this procedure was 16% of the starting UDP-[14C]GlcA. Establishment of a reliable method to synthesize and purify UDP-[14C]GalA will facilitate the identification and purification of the galacturonosyltransferase(s) involved in pectin biosynthesis.

Anions↗
PubMed1995

Effects of K+ on the binding of Ca2+ to the Ca(2+)-ATPase of sarcoplasmic reticulum.

Equilibrium and kinetic fluorescence methods have been used to characterize the interactions between K+ and the Ca(2+)-ATPase of skeletal-muscle sarcoplasmic reticulum. K+ shifts the E2-E1 equilibrium of the ATPase towards E1 and increases the rate of Ca2+ binding to the ATPase, as detected by changes in tryptophan fluorescence intensity, suggesting that K+ increases the rate of the E2-E1 transition. The data are consistent with binding of K+ at the inner Ca(2+)-binding site on the ATPase in competition with H+ and Mg2+, with a higher affinity in the E1 than in the E2 conformation. K+ has no effect on the affinity for Mg2+, as detected by changes in tryptophan fluorescence intensity; since it has been proposed that the changes in tryptophan fluorescence follow from binding to Mg2+ at the outer Ca(2+)-binding site, this suggests that K+ is unable to bind at the outer Ca(2+)-binding site. K+ increases the rate of dissociation of Ca2+ from the Ca(2+)-bound ATPase and reduces the effect of Mg2+ on the fluorescence intensity of the ATPase labelled with 4-(bromomethyl)-6,7-dimethoxycoumarin. It is suggested that these effects of K+ are the result of binding at a 'gating' site on the ATPase, in competition with binding of H+. Binding of K+ at the inner Ca(2+)-binding site and at the gating site account for the observed effects of K+ on the affinity of the ATPase for Ca2+.

Animals↗
PubMed1995

Serotonin and alcohol-related brain damage.

Preliminary results from the immunohistochemical examination of the brainstems of chronic alcoholics, suggest that alcohol may have a role in damage to the principal serotonergic (5HT) nuclei. This view is reinforced by evidence from previous animal experiments which demonstrated a reduction in 5HT neurons in the brains of alcohol-preferring rats and selective neurotoxicity to 5HT neurons following 5,6-dihydroxytryptamine-induced increased ethanol intake. It is speculated that, like other neurotoxins, alcohol or its metabolites cause degeneration of 5HT axons and axon terminals. It is possible that if axonal damage is sufficiently severe and chronic, the eventual consequence is cell death. This could be due to insufficient opportunity for repair and regrowth under repeated and sustained insults of high alcohol consumption.

5,6-Dihydroxytryptamine↗
PubMed1995

Nurse managers and their future in New South Wales.

The goal of International Perspectives is to share the views of nurse leaders, from countries other than the United States, on global healthcare issues. The focus is on identifying healthcare management problems and their implications, research priorities, policy development, and ethicalmoral dilemmas faced by nurse administrators. You are encouraged to send the names and addresses of international nurse leaders who might be interested in participating, as well as your ideas, for format and content of the department.

Forecasting↗
PubMed1995

A vesicouterine fistula caused by catheterization during delivery.

We report a case of a vesicouterine fistula occurring after catheterization during delivery in a women who had two previous Caesarian sections. Fistulae between the bladder and uterus are rare; they have been reported after prolonged and neglected labor 1 and after caesarian section. 2 This case followed catheter penetration of the bladder and thinned cervix during delivery.

Journal Article↗
PubMed1994

Rupture of the mitochondrial outer membrane impairs porin assembly.

Outer membranes isolated from yeast mitochondria were capable mediating the in vitro insertion of porin. As with the outer membrane of intact mitochondria, the insertion was ATP-dependent, and the inserted porin was resistant to trypsin treatment after detergent solubilization. However, the extent of porin insertion into isolated outer membranes was much less per mg of outer membrane protein than with intact mitochondria. The greater efficiency of intact mitochondria was not due to contact site-mediated translocation as isolated contact sites were less able to insert porin than isolated outer membranes, and blockade of the contact site channel in intact mitochondria did not affect porin insertion. However, mitochondria that had been subjected to osmotic shock sufficient to rupture the outer membrane and deplete the contents of the intermembrane space (i.e. mitoplasts) lost most of their ability to insert porin. Since outer membranes are isolated from mitoplasts, the low insertion activity of mitoplasts explains the low efficiency of insertion into isolated outer membranes. These results also indicate that, unlike proteins that are imported to the inner membrane and matrix of the mitochondria, porin's assembly is severely reduced by breaching the outer membrane and depletion of the intermembrane space contents.

Adenosine Triphosphate↗
PubMed1994

Focal and non-focal hepatic expression of placental glutathione S-transferase in carcinogen-treated rats.

Carcinogenesis develops in stages that have been operationally defined as initiation, promotion and progression. Although morphological end points have been described for detection and quantitation of these stages, to date initiation has been assessed only in the context of clonal growth in response to certain promoting agents. Initiated cells are morphologically indistinguishable from surrounding cells and early changes at the cellular level during initiation have not been clarified. One commonly used end point for the detection of preneoplastic hepatic lesions i their aberrant expression of the placental isozyme of glutathione S-transferase (PGST). Because single hepatocytes expressing PGST have been detected in aged rats and in those administered hepatocarcinogens, it has been suggested that such cells constitute a population of putatively initiated hepatocytes. In order to further elucidate the characteristics of single PGST-positive hepatocytes, we analyzed the number of these cells 2 and 18 weeks after various doses (0-100 mg/kg) of diethylnitrosamine (DEN) and of dimethylbenz[a]anthracene (DMBA). When determined 14 days after carcinogen administration, the number of single hepatocytes expressing PGST was greater after DEN administration (ranging from 0.8 +/- 0.3 per cm2 transection of liver at 1 mg/kg to 33.0 +/- 4.7 at 100 mg/kg) than after DMBA administration (ranging from 0.25 +/- 0.14 at 10 mg/kg to 3.03 +/- 0.5 at 100 mg/kg); none were detected in control rats of the same age. Additional rats were maintained on a basal diet or a basal diet plus phenobarbital for a further 4 month period. Whereas individual PGST-positive hepatocytes were only sporadically detected in rats treated with DMBA and maintained on a basal diet for 18 weeks, those rats placed on phenobarbital for 16 weeks had an even higher number of such PGST-positive hepatocytes than at 2 weeks after DMBA administration. In contrast, the dose-response curve observed for DEN-treated rats 18 weeks after carcinogen administration was similar to that observed 2 weeks after carcinogen treatment for both phenobarbital- and non-phenobarbital-treated rats. In addition, the number of single PGST-positive hepatocytes detected at 2 weeks was directly parallel to the number of altered hepatic foci expressing PGST 18 weeks after DEN administration. The dose-dependent induction of PGST-positive single hepatocytes after treatment with two hepatocarcinogens, the dose-dependent growth of altered hepatic foci (AHF) expressing PGST with phenobarbital administration and the parallel dose-response curve of single hepatocytes expressing PGST and later of AHF expressing PGST argue strongly for a precursor role of single PGST-positive cells in the development of AHF expressing PGST.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1994

Work practices, fatigue, and nuclear power plant safety performance.

This paper focuses on work practices that may contribute to fatigue-induced performance decrements in the commercial nuclear power industry. Specifically, the amount of overtime worked by operations, technical, and maintenance personnel and the 12-h operator shift schedule are studied. Although overtime for all three job categories was fairly high at a number of plants, the analyses detected a clear statistical relationship only between operations overtime and plant safety performance. The results for the 12-h operator shift schedule were ambiguous. Although the 12-h operator shift schedule was correlated with operator error, it was not significantly related to the other five safety indicators. This research suggests that at least one of the existing work practices--the amount of operator overtime worked at some plants--represents a safety concern in this industry; however, further research is required before any definitive conclusions can be drawn.

Fatigue↗
PubMed1993

Case-control study of leukaemia and non-Hodgkin's lymphoma among children aged 0-4 years living in west Berkshire and north Hampshire health districts.

OBJECTIVE: To investigate the relation between parental employment in the nuclear industry and childhood leukaemia and non-Hodgkin's lymphoma. DESIGN: Case-control study. SETTING-West Berkshire and Basingstoke and North Hampshire District Health Authorities. SUBJECTS: 54 children aged 0-4 years who had leukaemia or non-Hodgkin's lymphoma diagnosed during 1972-89, who were born in the study area and were resident there when cancer was diagnosed. Six controls were selected for each case: four from hospital delivery registers and two from livebirth registers maintained by the NHS central register. Controls were matched for sex, date of birth (within six months), and area of residence at birth and time of diagnosis. MAIN OUTCOME MEASURES: Parents' employment by the nuclear industry and exposure to ionising radiation at work. RESULTS: Five (9%) of the 54 cases and 14 (4%) of the 324 controls had fathers or mothers, or both, who had been employed by the nuclear industry (relative risk 2.2, 95% confidence interval 0.6 to 6.9). Nuclear industry employees who work in areas where exposure to radiation is possible are given film badges to monitor their exposure to external penetrating ionising radiation. Three fathers of cases and two fathers of controls (and no mothers of either) had been monitored in this way before their child was conceived (relative risk 9.0, 95% confidence interval 1.0 to 107.8). No father (of a case or control) had accumulated a recorded dose of more than 5 mSv before his child was conceived, and no father had been monitored at any time in the four years before his child was conceived. A dose-response relation was not evident among fathers who had been monitored. CONCLUSIONS: These results suggest that the children of fathers who had been monitored for exposure to external penetrating ionising radiation in the nuclear industry may be at increased risk of developing leukaemia before their fifth birthday. The finding is based on small numbers and could be due to chance. If the relationship is real the mechanisms are far from clear, except that the effect is unlikely to be due to external radiation; the possibility that it could be due to internal contamination by radioactive substances or some other exposure at work should be pursued. The above average rates of leukaemia in the study area cannot be accounted for by these findings.

Case-Control Studies↗
PubMed1993

Out-of-hospital resuscitation in East Sussex: 1981 to 1989.

OBJECTIVE: To assess the impact of extended training in advanced life support on the outcome of resuscitation. DESIGN: Analysis of the successful resuscitations from 1981 to 1989. SETTING: Brighton and East Sussex. RESULTS: 248 patients were resuscitated from cardiac or respiratory arrest in the community and subsequently survived to leave hospital. Their mean age was 64 years and one year survival was 77%. In most cases the cause of collapse was cardiac but 38 (15%) suffered a respiratory arrest. In 140 of the successful resuscitations (56%) collapse occurred before the arrival of the ambulance. Basic life support, with ventilation and chest compression where necessary, was sufficient to revive 35 (14%) of the patients. Defibrillation was also required in 107 patients (43%), and in a further 106 patients (43%) who had prolonged cardiorespiratory arrest requiring endotracheal intubation and the use of several drugs. Review of ambulance forms and case notes showed that in 87 cases (35%) the abilities of the paramedical ambulance staff in advanced resuscitation techniques contributed decisively to the success of resuscitation. These skills are illustrated by eight case reports. CONCLUSIONS: Extended training for ambulance staff increases the likelihood of successful resuscitation from out-of-hospital cardiopulmonary arrest. Though instruction in defibrillation must have the highest priority, full paramedical training can bring appreciable additional benefits.

Adolescent↗
PubMed1993

Schizophrenia in Nottingham: lifelong residential mobility of a cohort.

The lifetime geographical mobility of a group of 67 patients suffering from schizophrenia was investigated and related to the ecological structure of the city of Nottingham, where they first presented between 1978 and 1980. The study aimed to investigate the processes leading to a threefold rate of schizophrenia in the most socioeconomically deprived area of the city compared to the area of least deprivation. Results suggest that this skewed distribution begins early in the lives of the patients and is well established at least five years before initial contact with the psychiatric services.

Adolescent↗
PubMed1993

Mouthrinses in the prevention and treatment of periodontal disease.

Although the ideal topical antimicrobial does not exist, some marketed products possess many of the desirable characteristics of such an agent. Antimicrobial agents from a number of different chemical categories are being evaluated continuously. Recent clinical trials evaluating the effectiveness of chlorhexidine, stannous fluoride, prebrushing rinses, phenolic compounds, cetylpyridinium chloride, and new agents such as triclosan are described. Other trials involving special patient groups such as the elderly, mentally handicapped, and orthodontic patients, are discussed. Recent articles on alternative roles for topical antimicrobials are also identified.

Adult↗
PubMed1993

Costing services: comparing three i.v. medication systems.

Three methods of intermittent intravenous (IV) medication delivery were studied for evidence of cost effectiveness. Eighty-five patients receiving antibiotics on two general medicine units were examined over an eight-week period. Chi square analysis revealed no significant differences in the number of IV complications among the three delivery systems. ANOVA revealed no significant differences among the three systems. A cost savings of $99.70 per patient using the Bard system and $98.60 using the BD system was realized. Thirty-six (88%) of the nurses preferred a syringe pump system, 10 patients showed no strong preference for any of the methods, and the two pharmacists preferred a syringe delivery system.

Consumer Behavior↗
PubMed1992

Regulation of calbindin D 28K and its mRNA in the intestine of the domestic hen.

Intestinal calbindin synthesis in laying hens was analyzed to assess controlling factors operating during egg formation. In the absence of vitamin D, calbindin was not induced by estrogen and testosterone. In immature vitamin D-replete pullet, blood levels of 1,25(OH)2D3 increased in response to estrogen but the duodenal concentration of calbindin and its mRNA were increased only when testosterone was given together with estrogen. The plasma concentration of 1,25(OH)2D3 and the duodenal levels of calbindin and its mRNA were substantially higher in laying hens than in immature pullets. No differences in these parameters were observed between the stages of the ovulatory cycle. Suppression of shell formation for a week decreased the concentration of 1,25(OH)2D3 and of duodenal calbindin but did not affect the level of its mRNA. When egg shell formation resumed in hens previously laying shell-less eggs, the concentrations of 1,25(OH)2D3 and of calbindin and its mRNA increased toward the end of shell formation. A most important factor regulating intestinal calbindin synthesis in laying hens turned out to be 1,25(OH)2D3. Intestinal calbindin mRNA is more stable in laying hens than in young birds as its concentration declines more slowly when the stimulation provided by 1,25(OH)2D3 is withdrawn, as occurs following suppression of shell formation and after parathyroidectomy in laying birds. Intestinal calbindin mRNA is therefore increased by a process other than increasing 1,25(OH)2D3 formation. The factor influencing the stability of this mRNA in laying hens could be calcium. It is concluded that in hens the increased duodenal calbindin synthesis elicited by plasma 1,25(OH)2D3 at sexual maturity primarily involves a transcriptional process and the stabilization of the mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Estrogen and a calcium flux dependent factor modulate the calbindin gene expression in the uterus of laying hens.

The dependency of calbindin 28K synthesis on estrogen and vitamin D and its relationship with calcium transfer were investigated in the uterus of laying hens by dot blot hybridization analysis using as a probe a cDNA coding for calbindin. Estrogen stimulated growth of the oviduct and uterine calbindin synthesis in juvenile D-deficient female chicks. In laying hens, calbindin mRNA increased most markedly during shell deposition but calbindin concentrations did not fluctuate during the ovulatory cycle. Suppression of shell formation within a few hours reduced calbindin mRNA levels and lowered uterine calbindin concentrations when egg expulsions were continued for several days. The concentration of calbindin and its mRNA increased when shell formation resumed in hens previously laying shell-less eggs. These increases were maintained in hens parathyroidectomized just before shell resumption. Lowering dietary calcium decreased uterine calcium transfer and calbindin concentration but its mRNA level was unaffected. It is suggested that uterine calbindin synthesis is regulated in a tissue-specific manner through transcriptional mechanisms irrespective of change in vitamin D; calbindin synthesis is stimulated by estrogens as part of its effect on oviductal growth but its regulation predominantly involves a calcium flux dependent factor associated with shell calcification.

Animals↗