Search PubMed⌕ Search

Biomedical subjects

C J Johnson

Publications and source records attributed to C J Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Optimal gentamicin therapy in preterm neonates includes loading doses and early monitoring.

Recent studies have suggested the inadequacy of an initial gentamicin 2.5 mg/kg standard dose in neonates and the need for a loading dose. The purpose of this prospective, randomized study was to compare initial peak and initial trough serum gentamicin concentrations (SGC) in neonates after a standard dose (2.5 mg/kg) or a loading dose (4 mg/kg) on the first day of life. A secondary objective of the study was to evaluate the use of two SGC drawn after the first dose in designing individualized dosage regimens, despite the many changes in gentamicin disposition that occur over the first week of life. Forty infants admitted to the NICU were randomized to receive either 2.5 or 4 mg/kg gentamicin. Individual gentamicin pharmacokinetic parameters were determined after the first dose. Initial peak SGC were > 5 mcg/ml in only 6% of neonates receiving 2.5 mg/kg, versus 94% of neonates receiving 4 mg/kg. The initial trough after the first dose was < 2 mcg/ml in 100% of patients receiving 2.5 mg/kg and only 39% of patients receiving 4 mg/kg. Using two SGC after the first dose successfully predicted steady state peaks in 13/16 infants and steady state troughs in 14/16 infants. Thus, standard treatment of 2.5 mg/kg gentamicin yields initial peak serum gentamicin concentrations < 5 mcg/ml in neonates while a 4 mg/kg gentamicin loading dose, combined with pharmacokinetic monitoring after the first dose, optimizes gentamicin therapy in neonates.

Anti-Bacterial Agents↗
PubMed1996

Hormone therapy.

Explore the source record for details and available documents.

Cerebrovascular Disorders↗
PubMed1996

Technical results from the eversion technique of carotid endarterectomy.

A total of 167 carotid endarterectomies by the eversion technique were completed in 158 patients at a teaching hospital during the 6-year period ending July 1995. The average patient age was 66 years with a range of 39 to 89 years, and 99 (63%) were male. General anesthesia was employed routinely, and temporary indwelling shunts, were not used. Indications for endarterectomy included hemispheric transient ischemic attack (43), amaurosis fugax (20), stroke (41), and asymptomatic stenosis (63). Associated patient risk factors were not significantly different for men and women, and included diabetes mellitus (22%), tobacco abuse (72%), hypertension (69%), hypercholesterolemia (76%), cardiac disease (54%), and renal disease (21%). One (0.6%) permanent operative stroke and two (1%) 30-day hospital deaths occurred. Vascular laboratory follow-up was accomplished by duplex scanning with a documented sensitivity of 98 per cent in detecting a > or = 40 per cent stenosis. Eighty-nine per cent (148) of the 167 endarterectomies were tested at least once postoperatively. Overall laboratory follow-up averaged 17 months and ranged from one to 69 months. Residual stenosis, included perioperative thrombosis, occurred in 8 (5%) arteries. Recurrent stenosis was detected in four (2%) cases at 9, 24, 54, and 66 months after endarterectomy. Statistical analyses failed to implicate any specific patient risk factor, age, sex, or operative indication relevant to recurrent stenosis. Residual stenosis was correlated with younger patient age (P = 0.002), female gender (P = 0.12), and endarterectomy on the right side (P = 0.008). Carotid eversion endarterectomy appears to be a universally applicable, safe, and durable operative technique.

Adult↗
PubMed1995

Methylphenidate in the 'hard to wean' patient.

Patients on mechanical ventilation are occasionally hard to wean because of fatigue and/or depression. It is difficult to diagnose depression in this population, and treatment with traditional antidepressants has too slow an onset to be useful. Two cases are presented which suggest the possible utility of psychostimulants in this setting.

Aged↗
PubMed1995

Qualitative developments in the content and form of children's definitions.

This research examined qualitative developments in school-age children's (N = 96) expressible knowledge of a sample of 434 words selected to represent the contents of a large unabridged dictionary. Definitions were classified according to the quality of both semantic content and syntactic form. Analyses revealed developmental increases in the proportions of known words and in the relative proportions of definitions credited for high-quality content and/or form. Children generally were more successful in expressing precise semantic content than in using conventional syntactic form. The work characteristics of part of speech and morphological composition also affected definitional quality, with coordination of high-quality content and form achieved earlier for root and compound nouns than for inflected and derived nouns for verbs and adjectives of all morphological types. Both lexical organization and differential experience may support the earlier use of conventional definitional form for root and compound nouns than for other word types. The results provide a more complete picture of the development of definitional skills.

Child↗
PubMed1995

Advanced verb form production in story retelling.

This study investigated the rate at which 60 elementary school children produced three advanced verb forms--past progressive, past perfect progressive, and past perfect--when asked to retell literate narratives, a discourse genre that originates from written prose and frequently contains these advanced verb forms. The three verb forms were embedded in nine story episodes and told to the children. The children were then asked to retell the stories. Verb form production by the children was scored as either "borrowed" or substituted spontaneous production. During their story-retelling episodes, the 6-, 7-, and 8-year-old children borrowed all verb forms under investigation from the stimuli stories. They significantly preferred to borrow the past progressive over the past perfect progressive and past perfect forms. Rate of verb form production by 8-year-old children was significantly higher than for the younger age groups. These data suggest that advanced verb form production is influenced by the children's sensitivity to the type of narrative register (i.e., 1st or 3rd person perspective), the propositional ability associated with narrative development, and the progressive meaning of the -ing suffix.

Child↗
PubMed1995

Interrater reliability of an etiologic classification of ischemic stroke.

BACKGROUND AND PURPOSE: Precise identification of the cause of stroke is critical to research and clinical practice. Published series of ischemic stroke show considerable variation in the proportion of cases classified as atherosclerotic large-vessel disease, lacunar infarct, cardioembolic stroke, stroke of other known cause, and stroke of undetermined etiology. We describe the development and use of an etiology-specific classification of ischemic stroke. The interrater reliability of the classification is then evaluated. METHODS: A total of 160 cases of ischemic strokes in young adults were reviewed by paired neurologists who assigned cases to prioritized categories. The results of paired ratings were evaluated for each of the potential causes. Interrater agreement was assessed by means of kappa, which is the chance-adjusted percent agreement. RESULTS: For standard pairs, kappa was fair to good for all causes except lacunar stroke (kappa = 0.31); however, pair-to-pair variation was greatest for lacunar strokes. Strokes of undetermined cause and hematologic/other cause were of borderline fair reliability. CONCLUSIONS: The utility of a stroke classification system is dependent on its intended use. An etiologic classification is useful in studies of the epidemiology and pathophysiological basis of stroke. Fair to good reliability for an etiologic classification of stroke can be obtained when criteria are explicit.

Adolescent↗
PubMed1995

Effects of color on children's naming of pictures.

Two experiments assessed possible effects of memory for the typical colors of objects on children's naming of pictures. Children, 5 to 10 yr. old (N = 54 per experiment), named pictures of familiar objects in uncolored, typically colored (red for apple), and atypically colored (blue for apple) versions. Presentation of the three types of pictures was mixed in Exp. 1 and blocked in Exp. 2. With mixed presentation, reaction times for naming were unaffected by typical colors but slowed by atypical colors. With blocked presentation, naming was speeded by typical colors, but only for younger children, and was unaffected by atypical colors. Implications are discussed for understanding the processes by which objects are identified and named and the development of knowledge regarding the color of objects.

Association Learning↗
PubMed1994

Retrieval mechanisms in the development of instance and superordinate naming of pictures.

Children's use of superordinate names lags behind their use of instance names, and production lags behind comprehension. The hypothesis that both of these developmental delays reflect underlying retrieval difficulties predicts an interaction between name generality (instance vs. superordinate) and task (comprehension vs. production). Specifically, production of superordinate names should be more difficult for children than the separate name generality and task effects would predict. To examine this hypothesis, 32 junior kindergarten and 32 Grade 1 children in Experiment 1 performed an instance and superordinate name comprehension task for 96 single-exemplar pictures from 12 categories, and 32 junior kindergarten and 32 Grade 1 children in Experiment 2 produced instance or superordinate names for the same pictures. As predicted, the combination of superordinate names and language production was particularly difficult, especially for junior kindergarten children. High rates of instance name intrusions and other findings suggest that superordinate name production may be interfered with by more readily available instance names. Weak inhibition of competing instance names and other mechanistic explanations for the effects are considered.

Child↗
PubMed1993

Diagnosis of prostatic carcinoma: value of random transrectal sonographically guided biopsies.

OBJECTIVE: We studied the efficacy of random, transrectal sonographically guided biopsies in the diagnosis of prostatic carcinoma in a high-risk population. SUBJECTS AND METHODS: During a 2-year period, 570 transrectal sonographically guided prostatic biopsies were done because of clinical findings suggestive of prostatic carcinoma. Biopsies of hypoechoic lesions that were suggestive of carcinoma and segmental random biopsies of normal-appearing lobes of the prostate were performed. Transrectal sonographic findings were correlated with results of pathologic examination of the biopsy specimen and with surgical results, when available. RESULTS: Of the 202 patients found to have carcinoma, the carcinoma was detected with directed biopsy in 145 patients (72%). One hundred twenty (71%) of 169 carcinomas were detected with random biopsy when that procedure was performed. Random biopsies were the only method of diagnosing 57 (28%) of the 202 carcinomas, increasing the yield by 39%. CONCLUSION: Yield of carcinoma on transrectal sonographically guided biopsies increases significantly when segmental random biopsies are performed. Transrectal sonographically guided biopsies should include cores through hypoechoic lesions that are suggestive of carcinoma and bilateral segmental random biopsies.

Biopsy, Needle↗
PubMed1993

Black-white differences in stroke risk among young adults.

BACKGROUND AND PURPOSE: Little information is available regarding black-white differences in stroke incidence in young adults. METHODS: Cerebral infarction and intracerebral hemorrhage rates among adults 15 to 44 years of age were studied in Baltimore City and Baltimore County for 1988. Diagnoses were based on neurologist review of data obtained from medical records at 41 hospitals by neurological nurses. RESULTS: The cerebral infarction rates per 100,000 were 22.8 for black males, 10.3 for white males, 20.7 for black females, and 10.8 for white females. The intracerebral hemorrhage rates per 100,000 were 14.2 for black males, 4.6 for white males, 4.8 for black females, and 1.5 for white females. CONCLUSIONS: Blacks had significantly (P < .05) higher rates than whites for both cerebral infarction and intracerebral hemorrhage. Cerebral infarction rates are high in Baltimore compared with Florence, Italy, or Stockholm, Sweden.

Adolescent↗
PubMed1993

Development of a pharmaceutical care system in a neonatal intensive care satellite pharmacy.

The development of a pharmaceutical care system for a neonatal intensive care unit satellite pharmacy from existing integrated clinical, distributive, and quality assurance activities is described. Components of practice already in place included pharmacotherapeutic monitoring, evaluations for childhood immunizations, monthly medication summaries, and daily follow-up on scheduled doses returned in the unit dose exchange carts. Pharmacists documented patient drug therapy consultations on a standard form. New elements of practice emphasized organization of patients' clinical data by problem, development of specific outcome-oriented standards of care for common neonatal conditions and disease states, and quality improvement activities that evaluated the appropriateness of patient monitoring and patient outcomes. Written standards of care for specific disease states improved clinical decision-making, documentation of pharmacists' performance, and communication about patient care with other health care professionals. Elements of pharmacy practice already in place may provide a good foundation for a structured pharmaceutical care system.

Documentation↗
PubMed1992

Cloning and expression of a cellular high density lipoprotein-binding protein that is up-regulated by cholesterol loading of cells.

Plasma membranes of cultured cells contain high affinity receptors for high density lipoprotein (HDL) that appear to mediate removal of excess intracellular cholesterol. Recent studies using ligand blot analysis have identified a 110-kDa membrane protein which has features predicted for an HDL receptor, in that it preferentially binds HDL apolipoproteins and undergoes up-regulation in response to cholesterol loading of cells. In this study, we isolated a cDNA clone from an expression library using an antibody raised against partially purified 110-kDa HDL-binding protein. This clone encodes a novel cell protein, designated HBP, comprised mostly of 14 imperfect tandem repeats of approximately 70 amino acids in length. Each repeat appears to contain two amphipathic helices. Expression of HBP in cultured cells was increased severalfold when cells were loaded with cholesterol, as evident by increases in both HBP mRNA and membrane-associated protein. Overexpression of HBP in mammalian cell transfectants was associated with higher HDL binding to isolated cell protein and with modest increases in HDL binding to the cell surface. Proteins identified by ligand blot analysis had lower apparent M(r) than the primary HBP gene product and varied in M(r) and in HDL binding activity between cell types, suggesting that HBP undergoes cell-specific processing. These results provide preliminary evidence that HBP is a component of a cellular pathway that facilitates removal of excess cholesterol from cells, perhaps through its interaction with HDL. However, the predicted structure of HBP does not conform to that of any known receptor, suggesting that it does not function as a classic plasma membrane receptor.

Amino Acid Sequence↗
PubMed1992

Cognitive components of naming in children: effects of referential uncertainty and stimulus realism.

The ease of picture naming in children was assessed as a function of two stimulus characteristics: (a) the number of available correct names for a picture (referential uncertainty) and (b) the degree to which a picture realistically represents the depicted object (stimulus realism). Two experiments employing different methods demonstrated that: (a) children named low uncertainty objects (those with a single dominant name, e.g., key, elephant) faster than high uncertainty objects (those with multiple possible correct names, e.g., lamp/light, stove/oven) and (b) this uncertainty effect arose at a stage of naming subsequent to object identification. Possible underlying mechanisms for the uncertainty effect include passive diffusion of activation over multiple object-name pathways or active inhibition among competing candidate names. Stimulus realism (colored photographs vs uncolored line drawings) did not consistently influence naming performance. Implications for understanding children's naming behavior are discussed.

Attention↗
PubMed1991

Non-dialogue speech during preschool interactions.

Young children's skilfulness in conversational interaction is of great importance in understanding pragmatic aspects of language development. The purpose of this investigation was to describe the portion of preschool verbal interaction which could not be considered successful dialogue. Ten dyads of four-year-olds were videotaped during free play. Segments of talk were identified as dialogue or non-dialogue. Non-dialogue was coded when one child did not appear to direct his/her utterances to the other or when an attempted topic failed to capture the interest of the other child. Thirteen types of non-dialogue were identified. Results revealed that all dyads exhibited non-dialogue, but differences were noted in regard to amount and type. Dyads labelled as less co-operative displayed greater amounts of self-directed talk (monologue).

Child Language↗
PubMed1990

Continuing importance of nitrate contamination of groundwater and wells in rural areas.

The contamination of groundwater and rural drinking water supplies by nitrates from livestock and human excrement, other organic waste, or chemical fertilizers is a potential hazard throughout the world. Infant illness and death from nitrate-induced methemoglobinemia is probably often misdiagnosed, perhaps as sudden infant death syndrome, and certainly contributes to the national infant death rate statistics. A 1950 report listed 144 cases of infant methemoglobinemia with 14 deaths in one 30-month period in Minnesota. Infant deaths resulting from misdiagnosis of this preventable, treatable intoxication were still occurring as recently as 1986 in South Dakota. In this state, about 39% of dug or bored wells were unsafe due to high nitrate content, compared with 22% of drilled wells and 16% of driven wells. Properly constructed wells more than 30 m deep are more likely to be safe. Groundwater concentrations of nitrate may be unsafe for consumption, and standards are needed to regulate such contamination. Such standards could serve as guidelines and could be enforceable in the case of water systems dependent on wells.

Agriculture↗
PubMed1990

Lateral striatal cholinergic mechanisms involved in oral motor activities in the rat.

These experiments were undertaken to determine if local injection of pilocarpine in the neostriatum of the rat produces oral motor activities that are similar to those produced by systemic administration. In the first experiment, IP administration of 2.0-8.0 mg/kg pilocarpine increased chewing movements and tongue protrusions. In the second experiment, chronic guide cannulae were implanted bilaterally in ventromedial or ventrolateral striatum, and rats were injected with saline, 30, and 60 micrograms pilocarpine (per side). A dose-related increase in vacuous chewing was induced by injections of pilocarpine in the ventrolateral but not the ventromedial striatum. Tongue protrusions were induced by injections of pilocarpine into the ventromedial and the ventrolateral striatum. A third experiment demonstrated that this response was blocked completely by 10 micrograms scopolamine co-administered via the same cannulae, but the response was not reduced significantly by 10 micrograms haloperidol. These results indicate that ventrolateral striatal cholinergic mechanisms are involved in oral motor activities in the rat. This syndrome may provide a model for human clinical phenomena such as parkinsonian tremor.

Animals↗