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R L Davis

Publications and source records attributed to R L Davis.

At least 379 records · Page 21Linked to original sources
PubMed1966

Electrophoretic and Immunological Comparisons of Soluble Root Proteins of Medicago sativa L. Genotypes in the Cold Hardened and Non-Hardened Condition.

Electrophoretic and immunological properties of the soluble root protein complement of 6 Medicago sativa L. genotypes in the cold hardened and non-hardened physiological condition were compared. These 6 genotypes were chosen to represent a range of abilities to survive exposure to subfreezing temperatures when in the cold hardened condition.A zone of highly charged and/or low molecular weight protein components were found to be more prevalent in the protein complements of the cold-hardened material than the non-hardened material.Immunodiffusion plate tests were not so definitive as the electrophoretic patterns for identifying the genotypes or physiological conditions, but did corroborate the electrophoretic interpretations.

Journal Article↗
PubMedDate not supplied

Universal newborn hearing screening: summary of evidence.

CONTEXT: Each year, approximately 5000 infants are born in the United States with moderate-to-profound, bilateral permanent hearing loss (PHL). Universal newborn hearing screening (UNHS) has been proposed as a means to speed diagnosis and treatment and thereby improve language outcomes in these children. OBJECTIVES: To identify strengths, weaknesses, and gaps in the evidence supporting UNHS and to compare the additional benefits and harms of UNHS with those of selective screening of high-risk newborns. DATA SOURCES: We searched the MEDLINE, CINAHL, and PsychINFO databases for relevant articles published from 1994 to August 2001, using terms for hearing disorders, infants or newborns, screening, and relevant treatments. We contacted experts and reviewed reference lists to identify additional articles, including those published before 1994. STUDY SELECTION: We included controlled and observational studies of (1) the accuracy, yield, and harms of screening using otoacoustic emissions (OAEs), auditory brainstem response (ABR), or both in the general newborn population and (2) the effects of screening or early identification and treatment on language outcomes. Of an original 340 articles identified, 19 articles, including 1 controlled trial, met these inclusion criteria. DATA EXTRACTION: Data on population, test performance, outcomes, and methodological quality were extracted by 2 authors (D.C.T., H.M.) using prespecified criteria developed by the US Preventive Services Task Force. We queried authors when information needed to assess study quality was missing. DATA SYNTHESIS: Good-quality studies show that from 2041 to 2794 low-risk and 86 to 208 high-risk newborns were screened to find 1 case of moderate-to-profound PHL. The best estimate of positive predictive value was 6.7%. Six percent to 15% of infants who are missed by the screening tests are subsequently diagnosed with bilateral PHL. In a trial of UNHS vs clinical screening at age 8 months, UNHS increased the proportion of infants with moderate-to-severe hearing loss diagnosed by age 10 months (57% vs 14%) but did not reduce the rate of diagnosis after age 18 months. No good-quality controlled study has compared UNHS with selective screening of high-risk newborns. In fair- to poor-quality cohort studies, intervention before age 6 months was associated with improved language and communication skills by ages 2 to 5 years. These studies had unclear criteria for selecting subjects, and none compared an inception cohort of low-risk newborns identified by screening with those identified in usual care, making it impossible to exclude selection bias as an explanation for the results. In a mathematical model based on the literature review, we estimated that extending screening to low-risk infants would detect 1 additional case before age 10 months for every 1441 low-risk infants screened, and result in treatment before 10 months of 1 additional case for every 2401 low-risk infants screened. With UNHS, 254 newborns would be referred for audiological evaluation because of false-positive second-stage screening test results vs 48 for selective screening. CONCLUSIONS: Modern screening tests for hearing impairment can improve identification of newborns with PHL, but the efficacy of UNHS to improve long-term language outcomes remains uncertain.

Evidence-Based Medicine↗
PubMedDate not supplied

The cyclic AMP system and Drosophila learning.

The cyclic AMP (cAMP) system plays a critical role in olfactory learning in the fruit fly, Drosophila melanogaster, as evidenced by the following: [1] The dunce gene encodes a form of cAMP phosphodiesterase (PDE). Flies carrying mutations at this gene show reduced PDE activity, high cAMP levels, and deficits in olfactory learning and memory [2]. The rutabaga gene encodes one type of adenylyl cyclase (AC) similar in properties to the Type I AC characterized from vertebrate brain. This enzyme is activated by G-protein and Ca++ and has been postulated to be a molecular coincidence detector, capable of integrating information from two independent sources such as the conditioned stimulus (CS) and the unconditioned stimulus (US) delivered to animals during Pavlovian conditioning. Rutabaga mutant flies are deficient in AC activity and show behavioral defects similar to those exhibited by dunce mutants [3]. Flies carrying mutations in the gene (DC0) that encodes the catalytic subunit of protein kinase A (PKA), the major mediator of cAMP actions, show alterations in learning performance and a loss in PKA activity. All three genes are expressed preferentially in mushroom bodies, neuroanatomical sites that mediate olfactory learning. Interestingly, the PDE and the catalytic subunit of PKA are found primarily in axonal and dendritic compartments of the mushroom body cells, whereas the AC is found primarily in the axonal compartment. The reason for this differential compartmentalization is unclear, although the hypothetical role of AC as coincidence detector would predict that CS and US stimuli are integrated in the axonal compartment. These observations suggest that cAMP is a dominant second messenger utilized by mushroom body cells to modulate their physiology while the animal is learning and consolidating memory. However, many other types of molecules are likely involved in the physiological alterations that occur in these cells during learning, including cell surface proteins, transcription factors, and synaptic proteins.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMedDate not supplied

Bioavailability of selenium from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine, and sodium selenite assessed in selenium-deficient rats.

The bioavailability of selenium (Se) from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine (SeMet), and sodium selenite was assessed in Se-deficient Fischer-344 rats. Se as veal, chicken, beef, pork, lamb, flounder, tuna, SeMet, and sodium selenite was added to torula yeast (TY) basal diets to comprise Se-inadequate (0.05 mg Se/kg) diets. Se as sodium selenite was added to a TY basal diet to comprise a Se-adequate (0.10 mg Se/kg), Se-control diet. The experimental diets were fed to weanling Fischer-344 rats that had been subjected to dietary Se depletion for 6 wk. After 9 wk of the dietary Se repletion, relative activity of liver glutathione peroxidase (GSHPx) from the different dietary groups compared with control rats (100%) was: flounder 106%, tuna 101%, pork 86%, sodium selenite 81%, SeMet 80%, beef 80%, chicken 77%, veal 77%, and lamb 58%. Se from flounder was the most efficient at restoring Se concentrations in the liver and skeletal muscle. Se from sodium selenite, SeMet, beef, veal, chicken, pork, lamb, and tuna was not dietarily sufficient to restore liver and muscle Se after 9 wk of recovery following a 6-wk period of Se depletion.

Animals↗
PubMedDate not supplied

Definitive classes of childhood supratentorial neuroglial tumors. The Childhood Brain Tumor Consortium.

Our objective in this study was to identify histologically homogenous classes of childhood supratentorial neuroglial tumors. Previously, we identified five quantitative histologic factors (differing linear combinations of 17 reliably recognized histologic features in neuroglial tumors). They account for much of the histologic variance in the 703 supratentorial tumors in the Childhood Brain Tumor Consortium (CBTC) database. In this study, we used the scores on the factors in cluster analyses and identified eight classes of neuroglial tumors. Each of these classes had significant differences in histology, allowing the separation of many of the conventional types of neuroglial tumors into two or more classes. For instance, fibrillary astrocytoma, pilocytic astrocytoma, subependymal giant cell astrocytoma, anaplastic astrocytoma, oligodendroglioma, and ependymoma were represented in two or more classes. Often these classes had statistically significant differences in survival distributions. For instance, the two classes of "anaplastic astrocytomas" have widely discrepant 5-year survival probabilities of 0.7 and 0.2. Use of the classes identified in this study ensures relatively homogeneous histologic subsets of tumors. We suggest that these classes will be useful for the selection of children for therapeutic clinical trials.

Astrocytoma↗
PubMedDate not supplied

Fatality after report to a child abuse registry in Washington State, 1973-1986.

Between 1973 and 1986, 11,085 children born in Washington State were reported to the state child abuse registry. We analyzed the fatality rate subsequent to reported abuse for this cohort of children compared to a population of nonabused children matched on sex, county of birth, and year of birth. Children reported to the child abuse registry had an almost threefold greater risk of death than the comparison population. A report of physical abuse carried the greatest risk of subsequent death. However, the relative risks were also elevated for children who suffered neglect or sexual abuse. Children reported to the registry were almost 20 times more likely than the comparison population to die from homicide. Children less than 1 year of age at time of reported abuse had the highest fatality rate subsequent to abuse, but adolescents had the highest relative risk for fatality after abuse, compared to the population of nonabused children. Rates of fatality subsequent to abuse were equal for males and females. Although this study could not measure the extent to which any given intervention reduced the risk of subsequent fatality in abused children, registries can serve a valuable function in identifying subpopulations at risk and quantifying that risk relative to the general population.

Accidents↗
PubMedDate not supplied

Prospective randomized study comparing the efficacy and safety of ciprofloxacin with cefaclor in the treatment of patients with purulent bronchitis.

We compared safety and efficacy of ciprofloxacin and cefaclor in the treatment of patients with purulent bronchitis. Fifty-five patients were randomized prospectively to receive ciprofloxacin with a dose of 500 mg orally twice daily or cefaclor 250 mg over 8 hr for 5 days or longer. Patient groups did not differ with respect to age, duration of illness, severity of infection, or number of other concomitant disease states. A significantly larger number of patients in the ciprofloxacin group had poor health status (39.3% vs 7.4% for the ciprofloxacin and cefaclor groups, respectively, p = 0.02). The response to therapy did not differ between groups. Infection was completely resolved in 71.4% vs 66.7% and markedly improved in 7.1% and 11.1% for the ciprofloxacin and cefaclor groups, respectively. The response to therapy and adverse reaction rate did not differ between groups. Seven patients treated with ciprofloxacin and five patients treated with cefaclor developed adverse reactions. We conclude that ciprofloxacin is a useful agent for the treatment of purulent bronchitis.

Adult↗
PubMedDate not supplied

At least two genes reside within a large intron of the dunce gene of Drosophila.

The dunce locus of Drosophila melanogaster is considered to house a gene involved in memory, because flies carrying lesions at the locus have shortened memory of several different conditioned behaviours. Our recent partial characterization of the gene at the molecular level, along with prior genetic and biochemical evidence, recently provides compelling evidence that the gene codes for the enzyme cAMP phosphodiesterase. The observation that the gene encodes at least six overlapping poly(A)+ RNA molecules ranging in size from 4.2 to 9.5 kilobases (kb) (ref. 8), suggests that the gene is extraordinarily complex. Here we provide the sequence of a dunce complementary DNA clone and the corresponding genomic coding regions which show that the organization of the gene is elaborate. The cDNA clone defines dunce exons which are separated by a large intron of 79 kb. More importantly, at least two other genes are shown to reside within the large intron, including the well-defined glue protein gene, Sgs-4. The location of dunce exons relative to the molecular breakpoints of chromosomal aberrations with defined cytological positions indicates that the dunce gene extends over more than five polytene chromosome bands.

Animals↗
PubMedDate not supplied

Neuropathology of acquired immunodeficiency syndrome.

The nervous system is involved in the acquired immunodeficiency syndrome (AIDS) by infections and infestations, by neoplasms, and by several diseases of uncertain pathogenesis. The most common pathological abnormalities are the changes associated with the HIV agent itself, the 'HIV subacute encephalitis'; the most specific change is demyelination with multinucleate giant cells. Cytomegalovirus (CMV) is the most common secondary virus, but progressive multifocal leucoencephalopathy (PML) is more frequently seen at biopsy. Toxoplasmosis is the most common cause of abscess formation, but fungal infections, especially by cryptococcus, are more often the cause of meningitis. Mycobacterial infections and other opportunistic organisms are relatively rarely seen in the CNS. A vacuolar myelopathy of unknown pathogenesis is seen in AIDS; it involves the dorsal and lateral columns and the thoracic spinal cord most prominently. Endarteritis of unknown cause with resultant infarction is seen in children. Primary CNS lymphoma accounts for a major percentage of the lymphomas seen in AIDS; they are high grade tumours, are most often multiple, and are of B-cell origin. Metastatic Kaposi's sarcoma is very rare. Several peripheral neuropathies occur in AIDS, and recently a myopathy with small rod bodies has been reported.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

The AutoCyte preparation system for gynecologic cytology.

OBJECTIVE: To determine if thin-layer processing of cervicovaginal samples improves detection of cytologic abnormalities by reducing problems related to direct smear preparation. STUDY DESIGN: Eight hundred fifty-two cervical samples were collected as part of a multicenter trial of the CytoRich/AutoCyte system. The Cervex Brush was used for specimen collection. Following preparation of a conventional Papanicolaou smear, the brush was placed in a vial of fixative. A thinlayer CytoRich preparation was prepared by sedimentation following centrifugation through a density gradient and then stained by the AutoCyte Preparation System according to the manufacturer's guidelines. The two preparations were masked and screened, and a diagnosis was rendered. Abnormal results from were reviewed by a pathologist. The specimens were later unmasked and the diagnoses compared. RESULTS: CytoRich and conventional cervical cytologic smears detected an equivalent number of squamous intraepithelial lesions (SILs) (27 vs. 29) and atypical squamous cells of undetermined significance (ASCUS) (19 vs. 21). Both methods missed an equivalent number of SILs (four vs. five). CytoRich detected more infections (151 vs. 115) and had 66% fewer nonspecific inflammatory diagnoses. CytoRich also had fewer "limited" adequacy evaluations (211 vs. 236). CONCLUSION: CytoRich preps improve adequacy; increase detection of infections, such as candidiasis and trichomoniasis; and are accurate in the diagnosis of SILs. CytoRich appears to be an equivalent and possibly better preparation for cervicovaginal cytology.

Automation↗
PubMedDate not supplied

Rat middle cerebral artery occlusion: evaluation of the model and development of a neurologic examination.

We have examined the incidence and size of infarction after occlusion of different portions of the rat middle cerebral artery (MCA) in order to define the reliability and predictability of this model of brain ischemia. We developed a neurologic examination and have correlated changes in neurologic status with the size and location of areas of infarction. The MCA was surgically occluded at different sites in six groups of normal rats. After 24 hr, rats were evaluated for the extent of neurologic deficits and graded as having severe, moderate, or no deficit using a new examination developed for this model. After rats were sacrificed the incidence of infarction was determined at histologic examination. In a subset of rats, the size of the area of infarction was measured as a percent of the area of a standard coronal section. Focal (1-2 mm) occlusion of the MCA at its origin, at the olfactory tract, or lateral to the inferior cerebral vein produced infarction in 13%, 67%, and 0% of rats, respectively (N = 38) and produced variable neurologic deficits. However, more extensive (3 or 6 mm) occlusion of the MCA beginning proximal to the olfactory tract--thus isolating lenticulostriate end-arteries from the proximal and distal supply--produced infarctions of uniform size, location, and with severe neurologic deficit (Grade 2) in 100% of rats (N = 17). Neurologic deficit correlated significantly with the size of the infarcted area (Grade 2, N = 17, 28 +/- 5% infarction; Grade 1, N = 5, 19 +/- 5%; Grade 0, N = 3, 10 +/- 2%; p less than 0.05). We have characterized precise anatomical sites of the MCA that when surgically occluded reliably produce uniform cerebral infarction in rats, and have developed a neurologic grading system that can be used to evaluate the effects of cerebral ischemia rapidly and accurately. The model will be useful for experimental assessment of new therapies for irreversible cerebral ischemia.

Animals↗
PubMedDate not supplied

Evaluation of 2,3,5-triphenyltetrazolium chloride as a stain for detection and quantification of experimental cerebral infarction in rats.

We have evaluated the use of 2,3,5-triphenyltetrazolium chloride (TTC) as an histopathologic stain for identification of infarcted rat brain tissue. The middle cerebral artery (MCA) of 35 normal adult rats was occluded surgically. At various times after surgical occlusion, rats were sacrificed and brain slices were obtained and stained with TTC or hematoxolin and eosin (H & E); the size of the area of infarcted tissue stained by each method was quantified. In rats sacrificed 24 hr after occlusion of the MCA, the size of the area of infarction was 21 +/- 2% of the coronal section for TTC, and 21 +/- 2% for H & E (mean +/- S.D., N = 13). The size of areas of infarction determined by either staining method was not significantly different in area by the paired test, and a significant correlation between sizes determined by each method was found by linear regression analysis (r = 0.91, slope = 0.89, and the y intercept = 4.4%). Staining with TTC is a rapid, convenient, inexpensive, and reliable method for the detection and quantification of cerebral infarction in rats 24 hr after the onset of ischemia.

Animals↗
PubMedDate not supplied

Developing a patient information brochure.

In light of increasing consumer demands for information and the growing complexity of healthcare facilities, the need has arisen to present the public with useful information concerning your medical group. A patient information brochure can be a valuable public relations device as well as a time saver. It can serve as a written record of key policies and procedures and can also be a morale builder for patients and staff. If your medical group has not yet developed a patient information brochure, you will be able to glean many practical tips from this article. Drawing from experience, the author traces through the steps of developing the brochure--from exploring current models and choosing an appropriate team for the project, through production details.

Group Practice↗
PubMedDate not supplied

Advice leads to success. The Durwood Medical Clinic, Inc.

When the Durwood Medical Clinic, Inc. of Charlotte, North Carolina, decided to either expand its existing facility or construct a new clinic, it sought the advice of administrators who had experienced the same situation. The group was advised to obtain assistance from experienced facility planners early in the project. By following the advice of consultants and builders, the group created not only a beautiful new building, but one that also was completed ahead of time and within budget.

Facility Design and Construction↗