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Biomedical subjects

J L Carson

Publications and source records attributed to J L Carson.

120 records · Page 7Linked to original sources
PubMed1976

Surface features of cirrhotic liver.

The surface features of single cells and of multicellular tissue units in cirrhotic rat livers have been studied by scanning electron microscopy (SEM). Cirrhosis of the liver was produced in rats by simultaneously treating them with carbon tetrachloride and sodium phenobarbital. Connective tissue septa consisted of a losse mesh-work of fibers in which fibroblasts were embedded. The arrangement and surface features of hepatocytes in cirrhotic nodules differed from those found in parenchyma of normal livers. Hepatocytes in cirrhotic nodules universally formed plates two cells thick. The portion of the hepatocyte surface covered by microvilli was greatly increased in cells from cirrhotic livers, and this was reflected in a corresponding reduction in the area occupied by the smooth-surfaced narrow intercellular space. Canaliculi between hepatocytes in cirrhotic livers were reduplicated and frequently branched. hepatocyte surfaces covered by microplicae and flattened microvilli, typical of connective tissue-facing surfaces in normal livers, were greatly increased in cirrhotic livers corresponding to the increase in connective tissue. Where hepatocytes directly contacted fibroblasts (and not fibers), their surfaces were entirely smooth. Sinusoidal endothelial cells in cirrhotic livers contained only isolated, relatively sparse pores, and they lacked both sieve plates (pore complexes) and large fenestrations.

Animals↗
PubMed1976

Effect of hepatic venous outflow obstruction on pores and fenestration in sinusoidal endothelium.

The ultrastructure of pores and fenestrations in hepatic sinusoidal endothelial cells was examined following partial surgical occlusion of the suprahepatic portion of the inferior vena cava. Within 12 h after partial obstruction of hepatic venous outflow, endothelial pores (less than 0-1 mum in diameter) and sieve plates in the distal halves of sinusoids were greatly reduced in number or were totally absent, and they were replaced by large fenestration (less than 1-0 mum in diameter). These results suggest that pores forming sieve plates may fuse to form large fenestrations. The findings also indicate that sinusoidal hypertension and hypoxia associated with obstruction of hepatic venous outflow alter the distribution of pores and fenestrations in sinusoidal endothelium

Animals↗
PubMedDate not supplied

Epidemiological pitfalls using Medicaid data in reproductive health research.

The purpose of this report is to discuss methodologic issues in using Medicaid claims data to conduct epidemiologic analyses in reproductive health. We conducted case-control studies that used Medicaid claims data to evaluate two specific reproductive health questions. Case and control pregnancies were selected from among 106,000 women identified in a Medicaid claims file. Medical record review was conducted for randomly selected cases and controls. Several methodological issues were identified. Women could contribute multiple pregnancies that qualified as either case pregnancies, control pregnancies, or both. The results of the medical record review indicated that 25% of one case group (low-birthweight infants) could not be confirmed, and 70% of the second case group (CNS birth defects) were misclassified. Thirty-five percent of women classified as not having undergone diagnostic ultrasonography based on Medicaid claims data had evidence of having received diagnostic ultrasound during pregnancy on the basis of medical record review. Several problems were encountered with the use of Medicaid billing data to address epidemiologic questions in reproductive health. Although solutions to some of these problems could be identified, others could not be addressed without careful review of the medical records. These limitations may not apply to all state Medicaid databases or other claims data, but they should be carefully considered when planning claims-based analyses of reproductive health issues.

Adolescent↗
PubMedDate not supplied

The impact of the night float system on internal medicine residency programs.

OBJECTIVE: To study the design, method of implementation, perceived benefits, and problems associated with a night float system. DESIGN: Self-administered questionnaire completed by program directors, which included both structured and open-ended questions. The answers reflect resident and student opinions as well as those of the program directors, since program directors regularly obtain feedback from these groups. SETTING/PARTICIPANTS: The 442 accredited internal medicine residency programs listed in the 1988-89 Directory of Graduate Medical Education Programs. RESULTS: Of the 442 programs, 79% responded, and 30% had experience with a night float system. The most frequent methods for initiating a night float system included: decreasing elective time (42.3%), hiring more residents (26.9%), creating a non-teaching service (12.5%), and reallocating housestaff time (9.6%). Positive effects cited include decreased fatigue, improved housestaff morale, improved recruiting, and better attitude toward internal medicine training. The quality of medical care was considered the same or better by most programs using it. The most commonly cited problems were decreased continuity of care, inadequate teaching of the night float team, and miscommunication. CONCLUSION: Residency programs using a night float system usually observe a positive effect on housestaff morale, recruitment, and working hours and no detrimental effect on the quality of patient care. Miscommunication and inadequate learning experience for the night float team are important potential problems. This survey suggests that the night float represents one solution to reducing resident working hours.

Attitude of Health Personnel↗
PubMedDate not supplied

Computer-assisted analysis of radial symmetry in human airway epithelial cilia: assessment of congenital ciliary defects in primary ciliary dyskinesia.

The ultrastructural analysis of cilia and diagnosis of primary ciliary dyskinesia (PCD) in biopsies of airway epithelium is sometimes confounded by poor sampling, inconsistencies in tissue quality and processing, and other technical problems. Although clinical findings may lead to a presumptive diagnosis, ultrastructural analysis of ciliary axonemes is the standard for confirmation of PCD. The ultrastructural features of the cilium when viewed in cross section by transmission electron microscopy confer a radial symmetry to the axoneme. Current digital image processing techniques can be applied to such images to reinforce signal, diminish noise, and confirm consistency of position of axonemal structures, a process that can augment ultrastructural analysis for PCD. In this study, computer-assisted digital image processing was used to evaluate cross sections of cilia in airway epithelial biopsies from patients previously diagnosed with PCD as well as in control subjects with normal cilia. These studies supported the original diagnoses and provided some new insights into axonemal organization in PCD. This technique is simple and may be useful in providing a supporting means for confirming or ruling out a diagnosis of PCD in cases that appear equivocal.

Chronic Disease↗
PubMedDate not supplied

Pathogenesis of respiratory infections due to influenza virus: implications for developing countries.

The influenza viruses have an important and distinctive place among respiratory viruses: they change antigenic character at irregular intervals, infect individuals of all ages, cause illnesses characterized by constitutional symptoms and tracheobronchitis, produce yearly epidemics associated frequently with excess morbidity and mortality, and predispose the host to bacterial superinfections. Much is known about influenza viruses, but their role in respiratory infections among children in developing countries is poorly understood, and the risk factors that lead to the excess morbidity and mortality have not been identified clearly. Among the many risk factors that may be important are alterations in host immunity, malnutrition, prior or coincident infections with other microorganisms, inhaled pollutants, and lack of access to medical care. There is a great need for research that can establish more precisely the role these and other unidentified factors play in the pathogenesis of influenza infections in children in the developing world.

Air Pollution↗
PubMedDate not supplied

Host-pathogen interactions in experimental Mycoplasma pneumoniae disease studied by the freeze-fracture technique.

The application of freeze-fracture and organ culture technology to the study of disease caused by Mycoplasma pneumoniae provided a new perspective on host-pathogen interactions. Structural variations of the M. pneumoniae membrane and alterations of the host cell membrane that are induced by this pathogen during experimental infection were observed. Study of freeze-fracture preparations of M. pneumoniae revealed the presence of numerous membrane-associated particles embedded in the inner aspect of the bimolecular leaflet. However, areas of the fractured membrane of cells sometimes had particle-free zones and/or blebs. These particle-free areas were sometimes closely aligned to host tracheal epithelium in organ culture. In addition, marked changes in the membrane integrity of the host epithelium during experimental infection were observed. Deterioration of luminal surface membranes and alterations in the distribution of ciliary intramembranous particles were frequently noted. Ciliary dysfunction was also suggested by observations of abnormally aligned and clumped adjacent cilia. These findings correlated well with biochemical data demonstrating altered host macromolecular synthesis and observations of ciliostasis during experimental M. pneumoniae infection.

Animals↗
PubMedDate not supplied

Microtubular discontinuities as acquired ciliary defects in airway epithelium of patients with chronic respiratory diseases.

A critical relationship exists between ordered ciliary ultrastructure and optimal mucociliary clearance in the respiratory airways. Structurally defective cilia derived from heritable syndromes or from epithelial cell injury may promote or exacerbate chronic disease processes. A lesion of airway epithelial cilia characterized by microtubular discontinuities and previously associated with primary ciliary dyskinesia (PCD) has been documented in other forms of chronic airways diseases, including cystic fibrosis (CF). Nasal cilia obtained by curettage of the inferior nasal turbinate from 89 patients without CF but exhibiting symptoms favoring PCD were evaluated by transmission electron microscopy. Of the 89 patients in the study group, 19 (21.4%) were diagnosed with PCD. Among the PCD patients, 16 (84.2%) exhibited microtubular discontinuities. Nine patients from this group without ultrastructural evidence of PCD also exhibited these defects, however. Furthermore, seven of eight nasal biopsy specimens from patients with CF in a separate disease control group exhibited microtubular discontinuities. Microtubular discontinuities were quantitatively negligible among control groups of healthy human subjects and individuals experimentally and naturally subjected to acute airway injury. These data provide evidence that ciliary microtubular discontinuities represent acquired ciliary defects reflective of chronic airway disease injury and are not components of a primary structural abnormality in PCD.

Adult↗
PubMedDate not supplied

Evaluation of penicylinders used in disinfectant testing: bacterial attachment and surface texture.

Two possible deficiencies in the AOAC use-dilution method for registration of chemical disinfectants by the Environmental Protection Agency are examined: (1) the physical disparities among brands of penicylinders and (2) the variability of bacterial numbers on penicylinders depending upon test strain and penicylinder surface texture. Textural differences of 2 brands of stainless steel penicylinders, one brand of porcelain, and one brand of glass were assessed by scanning electron microscopy. A considerable variation in smoothness of both inner and outer surfaces of stainless steel and porcelain penicylinders was observed. Glass penicylinders were very smooth. Numbers of bacteria attached to a penicylinder were assessed by vortexing the penicylinders 30 s at No. 4 after using the AOAC method of bacterial inoculation and drying 40 min at 37 degrees C. With this methodology, stainless steel carriers retained the 3 AOAC-recommended bacterial test strains differentially: ca 10(7) for Pseudomonas aeruginosa, 5 X 10(6) for Staphylococcus aureus, and 10(6) for Salmonella choleraesuis; glass retained 10(6)-10(7) organisms of all 3 test strains; porcelain retained about that amount of S. aureus but 10(5)-10(6) P. aeruginosa and 10(3)-10(4) S. choleraesuis. These data suggest that disinfectants are not similarly challenged with the AOAC-recommended test bacteria and that an alternative method should be considered to ensure comparable numbers of bacteria on penicylinders.

Bacteria↗
PubMedDate not supplied

Gastrointestinal tract bleeding associated with naproxen sodium vs ibuprofen.

BACKGROUND: The risk of gastrointestinal tract bleeding requiring hospitalization associated with naproxen sodium was compared with that with ibuprofen, using a prescription database to approximate over-the-counter dosing. OBJECTIVE: To evaluate the safety of naproxen sodium. METHODS: A claims database containing Ohio Medicaid data from January 1986 through February 1993 and Michigan Medicaid data from April 1983 through July 1993 was used to compare 101,318 patients dispensed naproxen sodium with 277,601 patients dispensed ibuprofen. Using a case-cohort design, all 59 patients from the full cohort who had been hospitalized with upper gastrointestinal tract bleeding (UGIB) that developed within 14 days after the first prescription for the study drugs were compared with a subcohort made up of a 10% random sample of subjects selected from the combined drug cohorts. RESULTS: The incidence of UGIB occurring within 14 days after the first prescription in the naproxen sodium cohort was 26 (0.026%) of 101,318 (95% confidence interval [CI], 0.017%-0.038%), compared with 33 (0.012%) of 277,601 patients (95% CI, 0.008%-0.017%) in the ibuprofen cohort. Overall, the use of naproxen sodium vs ibuprofen was associated with an adjusted relative risk of 2.0 (95% CI, 1.1-3.8). Among people with multiple prescriptions, the crude relative risk for those receiving therapy in a dose typical of over-the-counter use was 4.1 (95% CI, 1.2-13.8). CONCLUSIONS: The overall incidence of UGIB is low with both drugs. There is little additional absolute risk posed by the use of low-dose naproxen sodium, compared with low-dose ibuprofen, despite an increased relative risk. However, given the widespread use of these drugs, a substantial number of additional cases of UGIB could result from use of naproxen sodium. This increased risk should be considered, especially for patients whose baseline risk of UGIB is elevated.

Adolescent↗