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Biomedical subjects

C Baker

Publications and source records attributed to C Baker.

At least 55 records · Page 3Linked to original sources
PubMed1997

Crystalluria and urinary tract abnormalities associated with indinavir.

BACKGROUND: Indinavir, a protease inhibitor widely used to treat patients with HIV infection, has been associated with nephrolithiasis. Distinctive urinary crystals and a spectrum of urologic disorders were noted in patients receiving indinavir. OBJECTIVE: To determine the composition of urinary crystals and the frequency of asymptomatic crystalluria and urinary tract symptoms in patients receiving indinavir. PATIENTS: Patients with HIV infection who were enrolled in studies conducted at the National Institutes of Health. MEASUREMENTS: Microscopic urinalysis, high-performance liquid chromatography (HPLC) and mass spectrometry of urinary crystals and stones, and clinical evaluation of patients with urologic symptoms. RESULTS: Of 240 patients receiving indinavir, 142 provided urine specimens for analysis. Twenty-nine (20%) had crystals consisting of plate-like rectangles and fan-shaped or starburst forms. Mass spectrometry and HPLC confirmed that these crystals were composed of indinavir. Of 40 patients who were not receiving indinavir, none had similar crystals (P < 0.001). Nineteen of the 240 patients receiving indinavir (8%) developed urologic symptoms. Of these, 7 (3%) had nephrolithiasis and the other 12 (5%) had previously undescribed syndromes: crystalluria associated with dysuria and crystalluria associated with back or flank pain. Four of the patients with the latter syndrome had radiographic evidence of intrarenal sludging. CONCLUSIONS: Indinavir forms characteristic crystals in the urine. This crystalluria may be associated with dysuria and urinary frequency, with flank or back pain associated with intrarenal sludging, and with the classic syndrome of renal colic.

Adult↗
PubMed1997

Release of RANTES from nasal and bronchial epithelial cells.

RANTES is a chemokine with eosinophil attractant and activating activities. This study was undertaken to determine whether primary cultures of human nasal and primate bronchial epithelial cells produce RANTES and the effect of various cytokines and dexamethasone on the release of this chemokine. Nasal epithelial cells from 32 patients (HNE) and bronchial epithelial cells from 17 Macaca nemestrina monkeys (PBE) were cultured in vitro for 24 to 72 h with LPS, TNF-alpha, IL-1 beta, IFN-gamma and TNF-alpha combined with IFN-gamma and/or dexamethasone at 10 to 1000 micrograms/ml. Culture supernatants were assayed for RANTES by ELISA. RANTES synthesis was measured by immunoprecipitation. HNE and PBE released modest constitutive amounts of RANTES (350 to 1000 pg/ml) which did not increase with time in culture. Release of RANTES was stimulated by all activators except LPS in a time-dependent manner, with the greatest synthesis induced by the combined addition of TNF-alpha and IFN-gamma. The combination of these activators also increased RANTES synthesis as determined by immunoprecipitation. Dexamethasone at 100 and 1000 micrograms/ml produced significant inhibition of stimulated RANTES release. These data indicate that normal nasal and bronchial epithelial cells release RANTES which is upregulated by various cytokines and inhibited by dexamethasone. The enhanced release is due to stimulation of both synthesis and secretion. Production of RANTES by epithelial cells could contribute to the inflammation that characterizes the respiratory tract in asthma and rhinitis and downregulation of RANTES by glucocorticoids may be one mechanism of the therapeutic effect of these agents.

Adult↗
PubMed1997

Cultural relativism and cultural diversity: implications for nursing practice.

This article examines the doctrine of cultural relativism in nursing practice. To introduce the issue, an overview of the intellectual history of cultural relativism is presented. The academic themes of the debate surrounding cultural relativism are illustrated with an example of the social controversy in France involving cultural relativism as used to defend the practice of female genital excision among immigrant communities. The dilemma faced by nursing in making cross-cultural judgments is then examined in the light of the academic and social debates. The article concludes with a theoretical resolution of the issue of cultural relativism for nursing practice that is based on hermeneutic philosophy.

Africa↗
PubMed1997

High affinity binding of pyrethroids to the alpha subunit of brain sodium channels.

Na+ channels are the primary molecular targets of the pyrethroid insecticides. Na+ channels consisting of only a type IIA alpha subunit expressed in Chinese hamster ovary cells responded to pyrethroid treatment in a normal manner: a sustained Na+ current was induced progressively after each depolarizing pulse in a train of stimuli, and this Na+ current decayed slowly on repolarization. These modified Na+ channels could be reactivated at much more negative membrane potentials (V0.5 = -139 mV) than unmodified Na+ channels (V0.5 = -28 mV). These results indicate that pyrethroids can modify the functional properties of the Na+ channel alpha subunit expressed alone by blocking their inactivation, shifting their voltage dependence of activation, and slowing their deactivation. To demonstrate directly the specific interaction of pyrethroids with the alpha subunit of voltage-gated Na+ channels, a radioactive photosensitive derivative, [3H]RU58487, was used in binding and photolabeling studies. In the presence of a low concentration of the nonionic detergent Triton X-100, specific pyrethroid binding to Na+ channels in rat brain membrane preparations could be measured and reached 75% of total binding under optimal conditions. Binding approached equilibrium within 1 hr at 4 degrees, dissociated with a half-time of approximately 10 min, and had K(D) values of approximately 58-300 nM for three representative pyrethroids. Specific pyrethroid binding was enhanced by approximately 40% in the presence of 100 nM alpha-scorpion toxin, but no allosteric enhancement was observed in the presence of toxins acting at other Na+ channel receptor sites. Extensive membrane washing increased specific binding to 89%. Photolabeling with [3H]RU58487 under these optimal binding conditions revealed a radiolabeled band with an apparent molecular mass of 240 kDa corresponding to the Na+ channel alpha subunit. Anti-peptide antibodies recognizing sequences within the alpha subunit were able to specifically immunoprecipitate the covalently modified channel. Together, these results demonstrate that the pyrethroids can modify the properties of cells expressing only the alpha subunit of Na+ channels and can bind specifically to a receptor site on the alpha subunit.

Amino Acid Sequence↗
PubMed1997

Adolescent TMJ tomography and magnetic resonance imaging: a comparative analysis.

The predictive value of radiographic tomography was assessed using magnetic resonance imaging as a definitive test of TMJ soft-tissue status in a predominantly asymptomatic adolescent sample. Eighty-two TMJs in 41 subjects (mean age = 12.5 years, range = 10 to 17 years) were independently evaluated using axially corrected tomography and magnetic resonance imaging. Tests of comparison and correlation were performed. Correspondence of tomographic classification to magnetic resonance imaging classification of nondisplacement (55%), reducing internal derangement (35%), or nonreducing internal derangement (10%) showed a significant relationship (P < .05). Tomography as a diagnostic test of abnormal disc position had a sensitivity of 0.43, a specificity of 0.80, a positive predictive value of 0.64, and a negative predictive value of 0.63. Tomography is inappropriate as a diagnostic test for TMJ internal derangement.

Adolescent↗
PubMed1996

Inhibition of neurotransmission by peptides containing the synaptic protein interaction site of N-type Ca2+ channels.

N-type Ca2+ channels bind directly to the synaptic core complex of VAMP/synaptobrevin, syntaxin, and SNAP-25. Peptides containing the synaptic protein interaction ("synprint") site caused dissociation of N-type Ca2+ channels from the synaptic core complex. Introduction of synprint peptides into presynaptic superior cervical ganglion neurons reversibly inhibited synaptic transmission. Fast EPSPs due to synchronous transmitter release were inhibited, while late EPSPs arising from asynchronous release following a train of action potentials were increased and paired-pulse facilitation was increased. The corresponding peptides from L-type Ca2+ channels had no effect, and the N-type peptides had no effect on Ca2+ currents through N-type Ca2+ channels. These results are consistent with the hypothesis that binding of the synaptic core complex to presynaptic N-type Ca2+ channels is required for Ca2+ influx to elicit rapid, synchronous neurotransmitter release.

Animals↗
PubMed1996

An investigation into the attitudes and practices of intensive care nurses towards verbal communication with unconscious patients.

This study attempted to investigate the attitudes and practices of intensive care nurses towards verbal communication with unconscious patients. A sample of five staff nurses working in an intensive care unit in Northern Ireland formed the basis for the study. The research design was non-experimental and descriptive-exploratory in nature, incorporating 4-hourly observational periods and structured interviews. Qualitative and quantitative analysis indicated that intensive care nurses spend on average 5% of their time verbally communicating with unconscious patients. Most of this communication involves informing the patient of immediate procedural matters or providing reassuring statements. Most intensive care nurses claim that verbal communication with unconscious patients is very important, and some ambiguity is apparent as to the unconscious patient's level of awareness. Major factors influencing communication are the patient's level of consciousness, the amount of physical care being given and the presence of relatives.

Coma↗
PubMed1996

An amino-terminal truncated progesterone receptor isoform, PRc, enhances progestin-induced transcriptional activity.

Previously we reported the identification of two unique progesterone receptor (PR) messenger RNA transcripts that encode a smaller PR isoform, termed the C-receptor (PRc). These two PR transcripts encode a protein that is N-terminally truncated, so that it lacks the first zinc finger of the DNA binding domain, but still contains a complete hormone binding region with sequences for dimerization and nuclear localization. We also have demonstrated the existence of a 60-kDa progestin-specific binding protein in progestin target cells using a monoclonal antibody directed to the C-terminus of PRs, suggesting that these two novel transcripts generate a truncated form of PR. In this paper, we address the hypothesis that the C-receptor arises from the initiation of translation of a methionine C-terminal to the methionine start sites that generate the larger 94-kDa A and 116-kDa B human PR isoforms. The studies shown here support the postulate that another downstream in-frame methionine within the PR-coding region can serve as a translation initiation site for the generation of a third PR protein. A partial PR complementary DNA, lacking the translation start sites for B- and A-receptors was translated in vitro. The synthetic protein product bound [3H]progestins and unlabeled progestins. The antiprogestin RU486 also competed for this binding. Transfection of this partial PR complementary DNA into PR-negative HeLa cells resulted in progestin-specific binding activity. Because the third PR isoform lacks the first zinc finger of the DNA binding domain, but contains sequences for dimerization, we reasoned that the C-receptor isoform would be transcriptionally in-active and not bind DNA directly. Surprisingly, however, in the presence of A- and/or B-receptors, we found that C-receptors can modulate the transcriptional activity of A- and/or B-receptors using a reporter gene. These studies emphasize that multiple receptor isoforms may have distinct biological properties, and that the truncated C-receptor may play a role in explaining some of the pleiotropic effects of progestins.

Antineoplastic Agents↗
PubMed1996

Subjective experience of symptoms in schizophrenia.

A qualitative study using the interpretive interactionism method was conducted to investigate the inner experiences of individuals with schizophrenia that surround, mobilize, and shape their awareness of, and responses to, the symptoms of their illness. Biographical data were collected from a purposive sample of 15 respondents suffering from this illness. Their narratives indicated that psychic pain dominated their lives; this theme was intertwined with the themes of lack of control, failure, and loss. Psychic pain was the key factor in informants' developing recognition of fluctuations in the course of their illness. The findings suggest that nurses may facilitate symptom monitoring in individuals who have schizophrenia, by attending to the emotional distress permeating every facet of their existence and by helping them look inward, to heighten their consciousness of specific components of psychic distress.

Adaptation, Psychological↗
PubMed1996

The surface morphology of the omasum of the African goat.

The microstructure of the omasum of the African goat was investigated macroscopically, as well as by scanning electron microscopy to determine how the omasum is anatomically specialised to enable the goat to graze and browse so successfully in the harsh environments of Africa. The omasum of the African goat was found to be more simple in structure than that of other domesticated ruminants. The omasal laminae were arranged in only 3 orders with the number of laminae varying between 27 and 33, considerably fewer than previously described for other goats, sheep or cattle. The large conical and unguiculiform papillae surrounding the reticulo-omasal orifice, as well as the hooked papillae present on the laminae, were more similar to those of wild ruminants that browsed than domestic grazing species. The papillae on the laminae were also found to be directionally orientated towards the orifices, which may suggest a "sieve mechanism' at the reticulo-omasal orifice and interlaminar spaces. In addition, it may suggest a directional movement of ingesta between the laminae. The stratified squamous epithelium lining the laminae and papillae was lightly keratinised which, along with the microplicae-like surface folds and pits of the superficial cells, indicated that it was functionally structured for absorption. These morphological specialisations of the omasal surfaces of the indigenous African goat demonstrated similarities with that of wild ruminants that are able to graze and browse.

Animals↗
PubMed1996

Observations on the micromorphology of the tropical rat mite Ornithonyssus bacoti (Hirst) as revealed by scanning electron microscopy.

Ornithonyssus bacoti (Hirst) is an important parasite of rodents. The characteristic shape of the dorsal and sternal shields and gnathosoma used as taxonomic characteristics was confirmed by scanning electron microscopy. The anal plate is distinctly pear-shaped with a pair of adanal setae lateral to the anal valves, a single postanal seta and a distinct dentate cribrum formed by peg-like projections. In the adult mites a peritreme extends anteriorly to the 1st coxa from the spiracle situated laterally between the 3rd and 4th coxa. The peritreme is an open canal protected by an overhanging dorsal ridge and lined with short peg-like aciculae. The gnathosoma includes a pair of pedipalps, a pair of protrusile chelicerae retracted into the hypostoma, and a serrate tritosternum ventrally. A unique feature to the normal setae of the pedipalps is a golf club-shaped seta which is found medially on the palp genu. A distinctive double-bladed 'palpal claw' or apotele is directed medially from the palp tibia. The pincer-like chela consists of a spear-like prong forming the moveable digit and a curved stylus-like fixed digit used to pierce the skin. Each leg ends with a pair of hooked tarsal claws and a pair of lateral comblike pretarsal appendages adjacent to the pulvillus. The pulvillus may be retracted, allowing the pretarsal operculum to function as a 'clasping organ' that enables the mite to clasp the hairs of the host during feeding.

Animals↗
PubMed1995

Longevity and Medicare expenditures.

BACKGROUND: In the United States, the elderly account for over one third of health care spending. The total population over the age of 65 is projected to increase, as is life expectancy beyond the age of 65. We studied current patterns of Medicare expenses according to age at death and the possible effect of future demographic changes on Medicare spending. METHODS: We used data from the Medicare program to estimate lifetime Medicare expenses for a sample of 129,166 beneficiaries, 65 or older, who died in 1989 and 1990, according to age at death. Spending for nursing home care not covered by Medicare was excluded. (Nursing home costs represent about 20 percent of total health care spending for the elderly and increase with age.) Through simulation, we assessed the lifetime payments by Medicare for enrollees who turned 65 in 1990 and those who will do so in 2020. RESULTS: Estimated lifetime Medicare payments (in 1990 dollars) ranged from $13,044 for persons who died at 65 years of age, to $56,094 for those who died at 80, to $65,633 for those who died at 101 or older. The payments associated with an additional year of life and the average annual payments over an enrolle's lifetime both decreased as the age at death increased. The estimated 7.9 percent increase in life expectancy beyond 65 years that will have taken place between 1990 and 2020 (19.1 years past the age of 65 in 2020, as compared with 17.7 years in 1990) was associated with an estimated increase of 2.0 percent in lifetime Medicare payments. Of the estimated $98 billion increase in total lifetime payments (in 1990 dollars) from the 1990 group to the 2020 group, 74.3 percent was due to the larger size of the original birth cohort who will reach the age of 65 in 2020, 22.5 percent to an increase in the proportion of that birth cohort projected to survive to 65 years of age, and 3.2 percent to improved life expectancy beyond 65. CONCLUSIONS: The effect on Medicare spending of increased longevity beyond the age of 65 may not be great. Total Medicare payments will be more substantially affected by the expected increase in the absolute number of elderly people.

Aged↗
PubMed1995

Temporary back and leg pain after bupivacaine and morphine spinal anaesthesia.

Transient neurological symptoms have been reported after hyperbaric lidocaine 5% spinal anaesthetics. We report a patient with neurogenic back and leg pain after uncomplicated bupivacaine and morphine spinal anaesthesia. A healthy 39-yr-old woman received 1.6 ml hyperbaric bupivacaine 0.75% and 250 micrograms morphine intrathecally. Two hours later, the patient experienced discomfort during suturing of the peritoneum and surgery was completed under general anaesthesia. Recovery was uncomplicated until 13 hr after intrathecal injection, when the patient complained of burning pain in her back extending to the front of the abdomen and similar pain in her thighs. Neurological consultation was obtained. Treatment was started with amitriptyline and the symptoms resolved slowly. Complete recovery occurred over three months. Further studies to assess symptoms after spinal anaesthesia are indicated.

Adult↗
PubMed1995

Comparison of case-finding methodologies for endometritis after cesarean section.

BACKGROUND: Endometritis is a possible complication of delivery among patients undergoing cesarean section, resulting in increased costs and patient morbidity. However, traditional case-finding methods for endometritis may not identify most cases. We compared various case-finding methods with a reference method to determine a simple and accurate method for collecting data on endometritis after cesarean section. METHODS: We reviewed charts of all patients undergoing cesarean section (N = 167) during March 1 through July 31, 1991. These data were compared with study case-finding methods that used microbiology data, infection report forms from nursing, and computerized reports linking patients undergoing cesarean section with intravenous antibiotic use data and admission and discharge diagnoses. RESULTS: Each case-finding method was compared separately with the reference method ("gold standard"), which was designed to capture all cases among the patients in the study population (N = 145). This review yielded nine cases of endometritis (infection rate of 5.4/100 procedures). The computerized report method linking patients who underwent cesarean section with antibiotic use had a positive predictive value of 0.53. Methods that used microbiology data and nursing report forms had lower positive predictive values of 0.18 and 0.20, respectively. CONCLUSIONS: In our institution, case finding for postcesarean endometritis by means of a computerized report linking patients undergoing cesarean section with i.v. antibiotic use data and admission and discharge diagnoses is the most effective method of detecting postcesarean endometritis. It also represents the most efficient use of the infection control department's resources.

Anti-Bacterial Agents↗
PubMed1995

Feasibility, accuracy and safety of magnetic resonance imaging in acute aortic dissection.

Magnetic resonance imaging (MRI) is the most accurate method of defining the morphology and haemodynamic features of thoracic aortic dissection. However, because of doubts about its safety in acute situations, its use has so far been confined to imaging chronic dissections. We present a prospective study of 50 patients thought clinically to have acute thoracic aortic dissection in which a rapid diagnosis was made by MRI.

Acute Disease↗
PubMed1995

Carotid artery trauma: a review of contemporary trauma center experiences.

PURPOSE: Many issues surrounding the management and outcome of carotid artery injuries remain controversial. The purpose of this study was to review a large contemporary experience with such injuries in the setting of designated trauma centers. METHODS: A statewide computerized trauma registry was used to identify all patients with injuries to the common or internal carotid arteries from October 1987 to June 1993. The records of 82 such patients were retrieved and analyzed. RESULTS: Overall mortality and stroke rates were 17% and 28%, respectively. Patients presenting with coma or shock had a particularly bad prognosis (50% and 41% mortality, respectively). Internal carotid injuries resulted in mortality and stroke rates of 21% and 41%, respectively, compared with 11% each for common carotid injuries. Patients with blunt injuries had a much higher stroke rate (56% vs 15%) but had lower mortality (7% vs 22%) than did patients with penetrating injuries. Airway compromise and associated injuries did not affect prognosis. Operative repair and percutaneous balloon occlusion had the best survival and functional outcomes. CONCLUSIONS: Operative repair offers the best chances for recovery in all categories of patients regardless of injury mechanism. Ligation is useful only as a last-resort lifesaving effort. Shock and neurologic impairment are poor prognostic factors but should not negate repair.

Adolescent↗
PubMed1995

The development of the self-care ability to detect early signs of relapse among individuals who have schizophrenia.

A qualitative study using interpretive interactionism investigated how individuals with schizophrenia develop an ability to detect early signs of relapse. A purposive sample of 15 respondents were interviewed about their illness experiences. Three sequential processes were identified. Responding reactively to psychic pain, initiated by a desire to escape from overwhelming distress, resulted in the differentiation of tolerable and intolerable pain. Refining perceptions of psychic pain followed and resulted in the identification of specific thoughts, feelings and behaviors associated with different levels of distress. Finally, actively reducing psychic pain resulted in a proactive surveillance for specific signs of increasing distress.

Adolescent↗