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Biomedical subjects

C H Johnson

Publications and source records attributed to C H Johnson.

At least 37 records · Page 2Linked to original sources

In vitro comparison of transfixation and standard full-limb casts for prevention of displacement of a mid-diaphyseal third metacarpal osteotomy site in horses.

OBJECTIVE: To compare transfixation and standard full-limb casts for prevention of in vitro displacement of a mid-diaphyseal third metacarpal osteotomy site in horses. SAMPLE POPULATION: 6 forelimbs from 6 horses euthanatized for reasons not related to the musculoskeletal system. PROCEDURE: A 30 degrees osteotomy was performed in the mid-diaphysis of the third metacarpal bone. Two 4.5-mm cortical bone screws were placed across the osteotomy site to maintain alignment during casting. Two 6.35-mm Steinmann pins were placed from a lateral-to-medial direction in the distal aspect of the radius. A full-limb cast that incorporated the pins was applied. An extensometer was positioned in the osteotomy site through a window placed in the dorsal aspect of the cast, and after removal of the screws, displacement was recorded while the limb was axially loaded to 5,340 N (1,200 lb). Pins were removed, and the standard full-limb cast was tested in a similar fashion. RESULTS: The transfixation cast significantly reduced displacement across the osteotomy site at 445 N (100 lb), 1,112 N (250 lb), 2,224 N (500 lb), and 4,448 N (1,000 lb), compared with the standard cast. CONCLUSION AND CLINICAL RELEVANCE: A full-limb transfixation cast provides significantly greater resistance than a standard full-limb cast against axial collapse of a mid-diaphyseal third metacarpal osteotomy site when the bone is placed under axial compression. Placement of full-limb transfixation casts should be considered for the management of unstable fractures of the third metacarpal bone in horses.

Animals↗

Short communication: survival of Escherichia coli O157:H7 in dairy cattle drinking water.

Cattle drinking water from two dairy farms was used in a study to determine the survival characteristics of the bacterial pathogen Escherichia coli O157:H7 and wild-type E. coli. The E. coli O157:H7 inoculum consisted of a consortium of isolates obtained from dairy cattle. Fresh manure was used as the source for the wild-type E. coli. In the water source from farm 1 the pathogens were present at both 5 and 15 degrees C during the 16-d duration of the study. In the water source from farm 2, the pathogens were detected at 5 degrees C through d 8 and through d 4 at 15 degrees C. The fecal indicator, wild-type E. coli, was always present when the pathogens were present.

Animals↗

Different circadian oscillators control Ca(2+) fluxes and lhcb gene expression.

Circadian biological clocks control many biological events, but the pathways by which these events are controlled are largely unknown. Based on a model suggesting that cytosolic-free calcium levels control the expression of the Lhcb gene in plants, we tested whether the circadian oscillation of free calcium is responsible for driving the rhythm of Lhcb expression. We found that these rhythms free-run with different periods in tobacco seedlings in constant conditions. Moreover, robust oscillations of Lhcb promoter activity continued in undifferentiated tobacco calli in the absence of Ca(2+) oscillations. Therefore, these two circadian rhythms are not linked hierarchically. These data provide evidence for separate circadian pacemakers controlling molecular events in plants.

Aequorin↗

Prevalence of selected maternal and infant characteristics, Pregnancy Risk Assessment Monitoring System (PRAMS), 1997.

PROBLEM/CONDITION: Certain maternal behaviors and experiences (e.g., unintended pregnancy, late entry into prenatal care, smoking cigarettes during pregnancy, and physical abuse during pregnancy) might be related to adverse reproductive outcomes (e.g., low birthweight, infant morbidity and mortality, and maternal morbidity). Information on the prevalence of these behaviors and experiences is needed to monitor trends over time, to increase understanding of maternal behaviors and experiences and their relation to perinatal and maternal outcomes, and to develop and assess programs and policies designed to reduce these adverse outcomes among pregnant women and their infants. REPORTING PERIOD: From 1993 through 1997. DESCRIPTION OF SYSTEM: The Pregnancy Risk Assessment Monitoring System (PRAMS) is a CDC-developed, ongoing, state- and population-based surveillance system designed to collect information on self-reported maternal behaviors and experiences that occur before, during, and shortly after pregnancy among women who deliver a live-born infant. A 14-page questionnaire is mailed to a sample of mothers that is randomly selected from state birth certificate records. The questionnaire is followed by two additional mailings and follow-up with nonresponders by telephone. Responses are accumulated during the calendar year, combined with birth certificate data, and then weighted to be representative of all mothers who had a live-born infant in the state. Data for 1997 from 13 states were examined. RESULTS: The prevalence of unintended pregnancy resulting in a live-born infant ranged from 33.9% to 50.0% in the 13 states. From 1993 through 1997, data from Georgia demonstrated a significant decreasing trend (p = .01) in unintended pregnancy, whereas this trend significantly increased in New York (p = .03). In most states, women who were younger (aged <20 years), had less than 12 years of education, were black, and received Medicaid were more likely to report an unintended pregnancy. In 1997, 16.6%-30.7% of women entered prenatal care after the first 3 months of pregnancy. In most states, women who were younger (aged <20 years), black, had lower levels of education, and received Medicaid were more likely to enter prenatal care late or not at all. Georgia and Washington experienced significant decreasing trends in smoking during pregnancy. Across the 13 states, 11.0%-23.9% of women reported smoking during pregnancy. In seven of 13 states, white women were more likely to smoke during pregnancy than black women. In eight of 13 states, smoking was significantly more prevalent among women who delivered a low birthweight infant than women who delivered a normal weight infant. In seven states, the proportion of women who initiated breast-feeding significantly increased from 1993 through 1997; the prevalence in 1997 ranged from 48.1% to 86.8%. Women who were most likely to breast-feed were older, more educated, white, and did not receive Medicaid. The state-specific prevalence of physical abuse during pregnancy by a husband or partner ranged from 2.4% to 5.6%. In most of these states, women who had less than a high school education and women who received Medicaid were more likely to report having been abused. INTERPRETATION: Findings indicate that many women report high-risk behaviors or experience high-risk conditions before, during, and shortly after pregnancy. Furthermore, several specific groups of women were significantly more likely to report these behaviors or experience these conditions. In many states, women who were younger, less educated, and Medicaid recipients were more likely to experience unintended pregnancy, enter prenatal care after the first 3 months of pregnancy or not at all, smoke during the last 3 months of pregnancy, and never initiate breast-feeding. PUBLIC HEALTH ACTION: These findings are useful for state agencies to monitor trends in behaviors and experiences and to design public health programs and policies that addre

Adult↗

Isolation of a Histoplasma capsulatum cDNA that complements a mitochondrial NAD(+)-isocitrate dehydrogenase subunit I-deficient mutant of Saccharomyces cerevisiae.

A cDNA library was prepared from Histoplasma capsulatum strain G-217B yeast cells and an apparently full-length cDNA for a subunit of the citric acid cycle enzyme NAD(+)-isocitrate dehydrogenase was identified by sequence analysis. Its predicted amino acid sequence is more similar to the IDH1 regulatory subunit of S. cerevisiae NAD(+)-isocitrate dehydrogenase than to the IDH2 catalytic subunit. After expression in S. cerevisiae from an S. cerevisiae promoter, it was shown to functionally complement an S. cerevisiae idh1 mutant, but not an idh2 mutant, for growth on acetate as a carbon source and for production of NAD(+)-isocitrate dehydrogenase enzyme activity. These results confirm that the H. capsulatum cDNA encodes a homologue of subunit I of the S. cerevisiae mitochondrial isocitrate dehydrogenase isozyme that functions in the citric acid cycle.

Acetates↗

A bioluminescence resonance energy transfer (BRET) system: application to interacting circadian clock proteins.

We describe a method for assaying protein interactions that offers some attractive advantages over previous assays. This method, called bioluminescence resonance energy transfer (BRET), uses a bioluminescent luciferase that is genetically fused to one candidate protein, and a green fluorescent protein mutant fused to another protein of interest. Interactions between the two fusion proteins can bring the luciferase and green fluorescent protein close enough for resonance energy transfer to occur, thus changing the color of the bioluminescent emission. By using proteins encoded by circadian (daily) clock genes from cyanobacteria, we use the BRET technique to demonstrate that the clock protein KaiB interacts to form homodimers. BRET should be particularly useful for testing protein interactions within native cells, especially with integral membrane proteins or proteins targeted to specific organelles.

Bacterial Proteins↗

Renilla luciferase as a vital reporter for chloroplast gene expression in Chlamydomonas.

The use of luciferases as reporters of gene expression in living cells has been extended to the chloroplast genome. We show that the luciferase from the soft coral Renilla reniformis (Rluc) can be successfully expressed in the chloroplast of Chlamydomonas reinhardtii. Expression of the rluc cDNA was driven by the promoter and 5' untranslated regions of the atpA gene. Western analysis with an anti-Rluc antibody detected a single polypeptide of 38 kDa in the luminescent cells. This is 3 kDa larger than native Rluc, and suggests that translation of the chimeric mRNA begins at the atpA start codon, 29 codons upstream from the rluc start site. We also show that the luminescence of the transformants was sufficient to enable imaging of colonies using a cooled CCD camera.

5' Untranslated Regions↗

Isolation of Arcobacter butzleri from ground water.

Arcobacter butzleri was isolated from a contaminated ground water source. These organisms, previously designated as aerotolerant Campylobacter, were capable of surviving in the ground water environment. Specific DNA probes were used to characterize the isolates in the initial identification and survival studies. Arcobacter butzleri was found to be sensitive to chlorine inactivation.

Campylobacter↗

Circadian programs in cyanobacteria: adaptiveness and mechanism.

At least one group of prokaryotes is known to have circadian regulation of cellular activities--the cyanobacteria. Their "biological clock" orchestrates cellular events to occur in an optimal temporal program, and it can keep track of circadian time even when the cells are dividing more rapidly than once per day. Growth competition experiments demonstrate that the fitness of cyanobacteria is enhanced when the circadian period matches the period of the environmental cycle. Three genes have been identified that specifically affect circadian phenotypes. These genes, kaiA, kaiB, and kaiC, are adjacent to each other on the chromosome, thus forming a clock gene cluster. The clock gene products appear to interact with each other and form an autoregulatory feedback loop.

Adaptation, Physiological↗

Forty years of PRCs--what have we learned?

What are phase-response curves (PRCs)? How can they be measured? How should they be plotted? These questions and many other fascinating facets of PRCs are addressed in this review, including research topics in which phase-resetting data have provided crucial insights: entrainment, phototransduction, pacemaker mechanism, phase markers of the pacemaker, and gauges of oscillator amplitude. PRCs have enlightened us and will continue to be a valuable tool in clock research.

Activity Cycles↗

Expression of a gene cluster kaiABC as a circadian feedback process in cyanobacteria.

Cyanobacteria are the simplest organisms known to have a circadian clock. A circadian clock gene cluster kaiABC was cloned from the cyanobacterium Synechococcus. Nineteen clock mutations were mapped to the three kai genes. Promoter activities upstream of the kaiA and kaiB genes showed circadian rhythms of expression, and both kaiA and kaiBC messenger RNAs displayed circadian cycling. Inactivation of any single kai gene abolished these rhythms and reduced kaiBC-promoter activity. Continuous kaiC overexpression repressed the kaiBC promoter, whereas kaiA overexpression enhanced it. Temporal kaiC overexpression reset the phase of the rhythms. Thus, a negative feedback control of kaiC expression by KaiC generates a circadian oscillation in cyanobacteria, and KaiA sustains the oscillation by enhancing kaiC expression.

Amino Acid Sequence↗

Resonating circadian clocks enhance fitness in cyanobacteria.

In some organisms longevity, growth, and developmental rate are improved when they are maintained on a light/dark cycle, the period of which "resonates" optimally with the period of the endogenous circadian clock. However, to our knowledge no studies have demonstrated that reproductive fitness per se is improved by resonance between the endogenous clock and the environmental cycle. We tested the adaptive significance of circadian programming by measuring the relative fitness under competition between various strains of cyanobacteria expressing different circadian periods. Strains that had a circadian period similar to that of the light/dark cycle were favored under competition in a manner that indicates the action of soft selection.

Circadian Rhythm↗

Adaptive significance of circadian programs in cyanobacteria.

Prokaryotic cyanobacteria express robust circadian (daily) rhythms, even when growing with doubling times that are considerably faster than once every 24 h. This biological clock orchestrates cellular events to occur in an optimal temporal program. Competition experiments demonstrate that fitness is enhanced when the circadian period resonates with the period of the environmental cycle.

Adaptation, Physiological↗

The cyanobacterial circadian system: a clock apart.

Several new molecular components of the circadian clocks of animals, fungi, and bacteria have been unveiled in the past two years. Enough parts are now identified to indicate that there is more than one way to build a biological clock, although there are parallels in the cycling molecular events among disparate groups of organisms.

Animals↗

Live births resulting from unintended pregnancies: an evaluation of synthetic state-based estimates.

OBJECTIVES: Most states lack information on the proportion of live births resulting from unintended pregnancies. We evaluated a potential solution to the lack of data, a synthetic state-based estimate of the percentage of live births resulting from unintended pregnancies for the state of Georgia. METHODS: We constructed the synthetic estimate by standardizing the 1995 National Survey of Family Growth data by the race, marital status, and age distribution of Georgia residents ages 15-44 years who delivered a live birth during 1990-1994. Two surveys conducted in Georgia during the same period that collected information on unintended pregnancies were used for comparison: the Georgia Women's Health Survey (GWHS) and the Georgia Pregnancy Risk Assessment Monitoring System (PRAMS). RESULTS: The synthetic estimate (35.2%, 95% CI = 33.5%-36.7%) was not statistically different from the GWHS estimate (39.6%, 95% CI = 35.7%-43.5%), but was significantly lower than the Georgia PRAMS estimate (49.0%, 95% CI = 45.5%-52.5%). When we stratified by race, marital status, and age, the synthetic and GWHS estimates were statistically similar except for married females and females ages 25-34 years, for whom the synthetic estimates were lower. For all groups of females, the synthetic estimates were statistically lower than the Georgia PRAMS estimates. CONCLUSIONS: The synthetic estimate can be a useful method for states that need to know the overall magnitude of the percentage of live births resulting from unintended pregnancy for purposes such as program planning.

Adolescent↗