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Biomedical subjects

K E Koch

Publications and source records attributed to K E Koch.

29 records · Page 2Linked to original sources
PubMed1991

Use of ampicillin-sulbactam before and after formulary inclusion.

The use of ampicillin-sulbactam before and after the product was formally placed on a hospital formulary is described. In October 1987 the pharmacy and therapeutics committee at an acute-care institution granted ampicillin-sulbactam temporary formulary inclusion on the condition that its use be audited. Formal inclusion was to be based on the results of this preinclusion audit. A second audit was to be performed if formal inclusion was granted. The data were collated after each audit, and for each patient an infectious-disease consultant proposed an alternative antimicrobial regimen representing what would probably have been prescribed had ampicillin-sulbactam not been available. Sixty-four patients received the product during the six-month preinclusion audit period. Ampicillin-sulbactam was given to 37% of the patients for indications listed in FDA-approved labeling. The dosage was considered appropriate in 88% of the patients. Clinical outcome was considered successful in 84% of the patients who received the product for known infections. Therapy with ampicillin-sulbactam was less expensive (by $4125) in 35 patients and more costly (by $1523) in 29 patients; the projected annual savings were $7805. After formal inclusion on the formulary, ampicillin-sulbactam was prescribed for some 700 patients over a 16-month period. A review in 49 patients showed appropriate indication and dosage for 63% and 84% of the patients, respectively, and an 84% rate of therapeutic success. The extrapolated cost savings were $26,429 per year. After formulary inclusion, the use of ampicillin-sulbactam increased, as did the frequency of its use for indications appearing in FDA-approved labeling.

Ampicillin↗
PubMed1990

Postphloem, nonvascular transfer in citrus: kinetics, metabolism, and sugar gradients.

Postphloem, nonvascular assimilate transport occurs over an unusually long area in citrus fruit and thus facilitates investigation of this process relative to sugar entry into many sink structures. Labeled photosynthates moving into juice tissues of grapefruit (Citrus paradisi Macf.) slowed dramatically after entering the postphloem transport path (parenchyma cells, narrow portions of segment epidermis, and hair-like, parenchymatous stalks of juice sacs). Kinetic, metabolic, and compositional data indicated that transfer through the nonvascular area was delayed many hours by temporary storage and/or equilibration with sugars in compartments along the postphloem path. Labeled assimilates were generally recovered as sucrose throughout the path, and extent of hexose formation enroute bore no apparent relationship to the assimilate transfer process. Even after 24 hours, radiolabel was restricted to discrete, highly localized areas directly between vascular bundles and juice sacs. Postphloem transfer occurred against an ascending sucrose concentration gradient in young fruit, whereas a descending gradient (favoring diffusion/cytoplasmic streaming) developed only later in maturation. Involvement of a postphloem bulk flow is complicated in the present instance by the extremely limited water loss from juice sacs either via transpiration or fluid backflow. Nonetheless, tissue expansion can account for a collective water inflow of at least 1.0 milliliter per day throughout the majority of juice sac development, thus providing a modest, but potentially important means of nonvascular solution flow. Overall, data indicate postphloem transfer (a) can follow highly localized paths through sizable nonvascular areas (up to 3.0 centimeters total), (b) appears to involve temporary storage and/or equilibration with compartmentalized sugars enroute, (c) can occur either against an overall up-hill sugar gradient (young tissues) or along a descending gradient (near full expansion), and (d) appears to involve at least some contribution by nonvascular mass flow accommodated by tissue expansion.

Journal Article↗
PubMed1990

Use of standardized screening procedures to identify adverse drug reactions.

The development of an adverse drug reaction (ADR)-monitoring program using standardized screening procedures in a 650-bed hospital is described. A concurrent ADR-reporting system that relied on health-care professionals to report observed ADRs to the pharmacy had generated just two ADR reports during the previous year. The pharmacy developed a program that used standardized procedures to screen for ADRs. The Technicon computer was programmed to screen the previous day's orders for antidotes or "tracer" drugs. In addition, pharmacists screened all laboratory reports of serum drug concentration determinations and positive tests for Clostridium difficile toxin. Spontaneous reporting of ADRs by nurses and physicians was strengthened by use of a revised notification form, newsletters, and inservice-education programs. During the first seven months of the program, 298 ADRs were identified, 15 of which were submitted to FDA. The standardized screening procedures accounted for 149 reports. Pharmacists reviewed an average of 21 reports of high serum drug concentrations each month; on average, 11 of these reports involved ADRs. Screening of microbiology laboratory reports identified 29 ADRs. Physicians reported ADRs infrequently and were likely to report only serious or unexpected reactions. Nurses and pharmacists identified reactions sporadically. Quality assurance auditors were consistent in screening ADRs, but not all reported reactions proved to be ADRs. The use of standardized screening procedures was effective in this pharmacy-based ADR-monitoring program.

Antidotes↗
PubMed1989

Sucrose-metabolizing enzymes in transport tissues and adjacent sink structures in developing citrus fruit.

Juice tissues of citrus lack phloem; therefore, photosynthates enroute to juice sacs exit the vascular system on the surface of each segment. Areas of extensive phloem unloading and transport (vascular bundles + segment epidermis) can thus be separated from those of assimilate storage (juice sacs) and adjacent tissues where both processes occur (peel). Sugar composition, dry weight accumulation, and activities of four sucrose-metabolizing enzymes (soluble and cell-wall-bound acid invertase, alkaline invertase, sucrose synthase, and sucrose phosphate synthase) were measured in these transport and sink tissues of grapefruit (Citrus paradisi Macf.) to determine more clearly whether a given enzyme appeared to be more directly associated with assimilate transport versus deposition or utilization. Results were compared at three developmental stages. Activity of sucrose (per gram fresh weight and per milligram protein) extracted from zones of extensive phloem unloading and transport was significantly greater than from adjacent sink tissues during the stages (II and III) when juice sacs grow most rapidly. In stage II fruit, activity of sucrose synthase also significantly surpassed that of all other sucrose-metabolizing enzymes in extracts from the transport tissues (vascular bundles + segment epidermis). In contrast, sucrose phosphate synthase and alkaline invertase at this stage of growth were the most active enzymes from adjacent, rapidly growing, phloem-free sink tissues (juice sacs). Activity of these two enzymes in extracts from juice sacs was significantly greater than that form the transport tissues (vascular bundles + segment epidermis). Soluble acid invertase was the most active enzyme in extracts from all tissues of very young fruit (stage I), including nonvascular regions, but nearly disappeared prior to the onset of juice sac sugar accumulation. The physiological function of high sucrose synthase activity in the transport tissues during rapid sucrose import remains to be determined.

Journal Article↗
PubMed1988

Carbon Cost of the Fungal Symbiont Relative to Net Leaf P Accumulation in a Split-Root VA Mycorrhizal Symbiosis.

Translocation of (14)C-photosynthates to mycorrhizal (+ +), half mycorrhizal (0+), and nonmycorrhizal (00) split-root systems was compared to P accumulation in leaves of the host plant. Carrizo citrange seedlings (Poncirus trifoliata [L.] Raf. x Citrus sinensis [L.] Osbeck) were inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck and Smith. Plants were exposed to (14) CO(2) for 10 minutes and ambient air for 2 hours. Three to 4% of recently labeled photosynthate was allocated to metabolism of the mycorrhiza in each inoculated root half independent of shoot P concentration, growth response, and whether one or both root halves were colonized. Nonmycorrhizal roots respired more of the label translocated to them than did mycorrhizal roots. Label recovered in the potting medium due to exudation or transport into extraradical hyphae was 5 to 6 times greater for (+ +) versus (00) plants. In low nutrient media, roots of (0+) and (+ +) plants transported more P to leaves per root weight than roots of (00) plants. However, when C translocated to roots utilized for respiration, exudation, etc., as well as growth is considered, (00) plant roots were at least as efficient at P uptake (benefit) per C utilized (cost) as (0+) and (+ +) plants. Root systems of (+ +) plants did not supply more P to leaves than (0+) plants in higher nutrient media, yet they still allocated twice the (14)C-photosynthate to the mycorrhiza as did (0+) root systems. This indicates there is an optimal level of mycorrhizal colonization above which the plant receives no enhanced P uptake yet continues to partition photosynthates to metabolism of the mycorrhiza.

Journal Article↗
PubMed1986

Maternal serum alpha-fetoprotein screening, maternal weight, and detection efficiency.

Various methods of adjusting maternal serum alpha-fetoprotein levels based on maternal weight have been recommended in order to more appropriately assign risk in maternal serum alpha-fetoprotein screening. These adjustments may, however, result in a larger proportion of pregnancies designated as having increased risk and reduction in detection accuracy.

Body Weight↗
PubMed1984

Photosynthate partitioning in split-root citrus seedlings with mycorrhizal and nonmycorrhizal root systems.

Photosynthate partitioning was examined in seedings of sour orange (Citrus aurantium L.) and Carrizo citrange (Poncirus trifoliata [L.] Raf. x C. sinensis [L.] Osbeck) grown with split root systems inoculated on one side with vesicular-arbuscular mycorrhizal fungus (Glomus intraradices Schenck and Smith). Source-sink relations were studied without mitigating differences in mineral content or physiological age that can occur in separate plant comparisons, because phosphorus was evenly distributed between leaves on opposite sides of the seedlings. Above-ground portions of each plant were exposed to (14)CO(2) for 8.5 minutes and ambient air for 2 hours, followed by extraction and identification of labeled assimilates. Mycorrhizal halves of root systems accumulated 66 and 68% of the (14)C-labeled photosynthates translocated to roots of sour orange and ;Carrizo' citrange, respectively, as well as an average of 77% greater disintegrations per minute per gram fresh weight. Distribution of (14)C-labeled assimilates was independent of phosphorus effects on photosynthate partitioning in leaves and did not reflect fresh or dry weights of roots or degree of mycorrhizal dependency of the species. Differences in radioactivity between mycorrhizal and nonmycorrhizal root halves after 2 hours indicated at least 3 to 5% of the whole plant (14)C-labeled photosynthates were allocated to mycorrhizae-related events on one side and that twice this amount, or 6 to 10%, might be expected if the entire root system was infected.

Journal Article↗
PubMed1984

C-Photosynthate Partitioning and Translocation in Soybeans during Reproductive Development.

Partitioning and translocation of (14)C-photosynthates were examined during flowering and seed maturation in soybean (Glycine max [L.]Merr.) plants to quantify allocation to sugars, amino acids, organic acids, and starch and to study transport of C and N from leaves to reproductive sinks. The trifoliolate leaf at the eighth node was exposed to steady state levels of (14)CO(2) for 2 hours, followed by immediate extraction and identification of radioactive assimilates in the fed leaf blade, tissues of the transport path (e.g. petiole and stem), and fruits if they were present. About one-third of the total (14)C recovered from the leaf blades was in starch until late pod-filling, after which the proportion dropped to 16%. Sugars comprised 70% to 86% of the recovered (14)C from soluble assimilates of the source leaf, with highest proportions occurring during late flowering and early pod-filling. Amino acids accounted for 8% to 17% of the (14)C recovered from the soluble fraction, and were most evident during early flowering and mid to late pod-filling. The (14)C-organic acids comprised from 3% to 14% of the soluble (14)C-assimilates in leaves. Petioles consistently contained a higher percentage of recovered radioactivity in sugars (87-97%) and a lower percentage in amino acids (3-12%) than did leaf blades. (14)C-Amino acids in petioles attained their highest levels during mid and late pod-filling, while (14)C-organic acids comprised 2% or less of the recovered radioactivity after pod initiation. The distribution of (14)C-assimilates in the internode below the source leaf was similar to that found in petioles. A comparison of the above data to calculated C and N requirements for seed development suggests that (14)C-amino acids derived from current photosynthesis and translocated from source leaves supply at least 12% to 48% of the seed N depending on the stage of pod-filling.

Journal Article↗
PubMed1982

Crassulacean Acid Metabolism in the Succulent C(4) Dicot, Portulaca oleracea L Under Natural Environmental Conditions.

Crassulacean acid metabolism (CAM) was examined under natural environmental conditions in the succulent C(4) dicot Portulaca oleracea L. Two groups of plants were monitored; one was watered daily (well watered), while the other received water once every 3 to 4 weeks to produce a psi of -8 bars (drought stressed). Gas exchange, transpiration rate, and titratable acidity were measured for 24-hour periods during the growing season. CAM activity was greatest in drought-stressed plants during late August which had 13 hour days and day/night temperatures of 35/15 degrees C. Under these conditions net CO(2) uptake occurred slowly throughout the night. Diurnal fluctuations of titratable acidity took place in both leaves and stems with amplitudes of 17 and 47 microequivalents per gram fresh weight, respectively. Transpiration data indicated greater opening of stomata during the night than the day. CAM was less pronounced in drought-stressed P. oleracea plants in July and September; neither dark CO(2) uptake nor positive carbon balance occurred during the July measurements. In contrast, well-watered plants appeared to rely on C(4) photosynthesis throughout the season, although some acid fluctuations occurred in stems of these plants during September.To determine the fate of the CO(2) assimilated at night in drought-stressed Portulaca plants, exposure to (14)CO(2) during the night followed by 9 hours of ambient air in the light. Malate was the predominant compound labeled during the night, with some citrate and aspartate. No (14)CO(2) release was detected during the following day and by midafternoon the majority of the label was found in the insoluble fraction (predominantly starch). These results substantiate our earlier work with growth-chamber-grown plants and show that limited CAM activity can occur in the succulent C(4) dicot Portulaca oleracea L. under certain natural environmental conditions.

Journal Article↗
PubMed1982

Source-sink relations in maize mutants with starch-deficient endosperms.

Partitioning and translocation of photosynthates were compared between a nonmutant genotype (Oh 43) of corn (Zea mays L.) and two starch-deficient endosperm mutants, shruken-2 (sh2) and brittle-1 (bt1), with similar genetic backgrounds. Steady-state levels of (14)CO(2) were supplied to source leaf blades for 2-hour periods, followed by separation and identification of (14)C-assimilates in the leaf, kernel, and along the translocation path. An average of 14.1% of the total (14)C assimilated was translocated to normal kernels, versus 0.9% in sh2 kernels and 2.6% in btl kernels. Over 98% of the kernel (14)C was in free sugars, and further analysis of nonmutant kernels showed 46% of this label in glucose and fructose. Source leaves of mutant plants exported significantly less total photosynthate (24.0% and 36.3% in sh2 and bt1 compared to 48.0% in the normal plants) and accumulated greater portions of label in the insoluble (starch) fraction. Mutant plants also showed lower percentages of photosynthate in the leaf blade and sheath below the exposed blade area. The starch-deficient endosperm mutants influence the partitioning and translocation of photosynthates and provide a valuable tool for the study of source-sink relations.

Journal Article↗