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Biomedical subjects

J M Erickson

Publications and source records attributed to J M Erickson.

At least 19 recordsLinked to original sources
PubMed2000

Possible role of endogenous retinoid (Vitamin A) toxicity in the pathophysiology of primary biliary cirrhosis.

Primary biliary cirrhosis (PBC) is a chronic, cholestatic disease of unknown etiology commonly affecting women. It is characterized by progressive destruction of the small intrahepatic bile ducts and portal inflammation, leading to fibrosis and cirrhosis. The major signs and symptoms of PBC, which include pruritus, lethargy, the sicca syndrome, and osteoporosis, closely resemble the manifestations of hypervitaminosis A. Based on a review of the literature and other observations connecting PBC with retinoid metabolism (vitamin A and its derivatives), the hypothesis is proposed that exposure to excess endogenous retinoids contributes to the pathogenesis of PBC and may be to the cause of some of the signs and symptoms associated with the disease.

Adult↗
PubMed1999

Lipids increase after solitary pancreas transplantation.

OBJECTIVE: The aims of this study were to determine 1) changes in lipids after solitary pancreas transplantation (SPTX) in patients with type 1 diabetes and 2) factors that influence those changes. RESEARCH DESIGN AND METHODS: Lipids were evaluated prospectively in 24 patients who underwent SPTX. Three were excluded because of early graft failure. The remaining patients (n = 21; 13 men, 8 women) were studied for changes in lipids over time (pre-SPTX, 0-2, 3-6, 7-12, and > 12 months). Glycohemoglobin, serum creatinine, BMI, and medications were also analyzed for their effects on lipid changes. RESULTS: Cholesterol, HDL, and LDL decreased in the immediate postoperative period (0-2 months), whereas triglycerides (TGs) increased (P < 0.05). At 3-6 months, cholesterol, HDL, and TG were higher than before the SPTX, whereas LDL returned to pre-SPTX levels. After 12 months, HDL and TG remained higher than their pre-SPTX levels (P < 0.05). During the study, systolic and diastolic blood pressure increased, renal function decreased, glyco-hemoglobin improved, and weight was unchanged. Changes in cholesterol/HDL ratio, HDL, and TG correlated with changes in prednisone dose (P < 0.05), and changes in TG correlated with changes in creatinine (P < 0.05). The same pattern of lipids occurred in patients prescribed or not prescribed hypolipidemic agents. CONCLUSIONS: Lipids do not improve within the 1st year after SPTX, despite improved glycemic control and blood pressure control, and renal function is worse. These results are in contrast to those reported for combined kidney-pancreas transplantation, where lipids, blood pressure, and renal function improved immediately after transplant. Further studies are needed to determine whether lipids continue to change with time after SPTX. The impact of these changes after SPTX on overall cardiovascular risk is unknown.

Blood Pressure↗
PubMed1996

Anemia.

OBJECTIVES: To provide an overview of the disorders that cause anemia and to review clinical and laboratory assessment and medical and nursing management of the anemic patient. DATA SOURCES: Published articles and book chapters that pertain to red blood cell physiology and the major causes and types of anemia. CONCLUSIONS: Advances in molecular and genetic aspects of anemia are leading to new developments in the diagnosis and management of all types of anemia. Symptomatic relief to maintain quality of life is essential for all anemic patients. IMPLICATIONS FOR NURSING PRACTICE: Nurses can play a major role in the supportive care of patients with anemia through interventions related to pharmacological therapy, blood transfusions, nutritional counseling, and symptom management.

Anemia↗
PubMed1995

Peripheral intravenous myocardial contrast echocardiography using a 2% dodecafluoropentane emulsion: identification of myocardial risk area and infarct size in the canine model of ischemia.

OBJECTIVES: This study assessed the accuracy of 2% dodecafluoropentane (EchoGen), an intravenous echocardiographic contrast agent, in identifying myocardial area at risk and infarct size in the canine model of myocardial ischemia. BACKGROUND: Myocardial contrast echocardiography allows determination of myocardial area at risk and infarct size but requires intracoronary injection in humans. The development of agents that can be delivered by peripheral intravenous injection could enable bedside myocardial contrast echocardiographic assessment of risk area, infarct size and reperfusion. METHODS: Two protocols were used. Protocol 1 assessed the accuracy of myocardial contrast echocardiography using intravenous dodecafluoropentane in defining myocardial area at risk and infarct size in the canine model of regional myocardial ischemia versus gross pathologic specimens stained with monastral blue to determine area at risk and triphenyltetrazolium chloride to determine the area of necrosis. Protocol 2 assessed the effects of repeated injections of dodecafluoropentane (0.5 ml/kg body weight, four doses 30 min apart or eight doses 10 min apart) on myocardial blood flow and hemodynamic variables. RESULTS: Myocardial contrast echocardiography accurately defined area at risk and infarct size (r = 0.96 vs. triphenyltetrazolium chloride). Myocardial blood flow remained stable after multiple serial injections of dodecafluoropentane. However, a significant increase in pulmonary artery pressure and pulmonary vascular resistance, along with a decrease in arterial oxygen saturation and cardiac output, was seen in dogs that received eight injections at 10-min intervals. CONCLUSIONS: Myocardial contrast echocardiography using intravenous dodecafluoropentane accurately defined myocardial area at risk and infarct size. Hemodynamic variables and regional myocardial blood flows remained stable when dodecafluoropentane was injected at 30-min intervals for up to four doses; more frequent administration led to cardiopulmonary deterioration. Dodecafluoropentane offers the potential for reliable, noninvasive assessment of reperfusion after therapeutic interventions.

Animals↗
PubMed1995

Assembly of the Photosystem II oxygen-evolving complex is inhibited in psbA site-directed mutants of Chlamydomonas reinhardtii. Aspartate 170 of the D1 polypeptide.

Photosystem II catalyzes the photooxidation of water to molecular oxygen, providing electrons to the photosynthetic electron transfer chain. The D1 and D2 chloroplast-encoded reaction center polypeptides bind cofactors essential for Photosystem II function. Transformation of the chloroplast genome of the eukaryotic green alga Chlamydomonas reinhardtii has allowed us to engineer site-directed mutants in which aspartate residue 170 of D1 is replaced by histidine (D170H), asparagine (D170N), threonine (D170T), or proline (D170P). Mutants D170T and D170P are completely deficient in oxygen evolution, but retain normal (D170T) or 50% (D170P) levels of Photosystem II reaction centers. D170H and D170N accumulate wild-type levels of PSII centers, yet evolve oxygen at rates approximately 45% and 15% those of control cells, respectively. Kinetic analysis of chlorophyll fluorescence in the mutants reveals a specific defect in electron donation to the reaction center. Measurements of oxygen flash yields in D170H show, however, that those reaction centers capable of evolving oxygen function normally. We conclude that aspartate residue 170 of the D1 polypeptide plays a critical role in the initial binding of manganese as the functional chloroplast oxygen-evolving complex is assembled.

Animals↗
PubMed1994

Update on Hodgkin's disease.

Hodgkin's disease is a rare lymphoma usually diagnosed in adults presenting with painless lymphadenopathy. Treatment includes radiation therapy for early stages of the disease and chemotherapy for advanced stages. While the majority with Hodgkin's disease will be cured of their disease, patients must complete a period of therapy with risks of significant acute side effects and serious long-term complications. This article provides an overview of the natural history, diagnosis, and staging of Hodgkin's disease as well as a discussion about treatment modalities and associated complications.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

The eyespot of Chlamydomonas reinhardtii: a comparative microspectrophotometric study.

The eyespot of Chlamydomonas reinhardtii is believed to utilize a rhodopsin-like pigment in its responses to light. This paper examines its eyespot by means of microspectrophotometry with the finding of an absorption spectrum with two bands, an A-band in the blue, and a B-band in the green. This spectrum is identical to that previously recorded from the eyespot of Euglena gracilis. As with Euglena the B-band was found to have dichroic character and its spectrum was similar to the absorption curve of rhodopsin. This A-B-spectrum was always recorded from a single granule in each cell. It is concluded that both E. gracilis and C. reinhardtii may utilize a rhodopsin-like pigment as the photopigment associated with the eyespot response to light. In both these algae a few particles in each cell were found whose spectra consisted of two other bands, C and D, blue- and red-shifted, respectively, relative to the eyespot A-B-bands. There is some reason to believe that the C-D-granules may also be involved in certain light-controlled activities of the cells.

Animals↗
PubMed1989

Molecular and biophysical analysis of herbicide-resistant mutants of Chlamydomonas reinhardtii: structure-function relationship of the photosystem II D1 polypeptide.

Plants and green algae can develop resistance to herbicides that block photosynthesis by competing with quinones in binding to the chloroplast photosystem II (PSII) D1 polypeptide. Because numerous herbicide-resistant mutants of Chlamydomonas reinhardtii with different patterns of resistance to such herbicides are readily isolated, this system provides a powerful tool for examining the interactions of herbicides and endogenous quinones with the photosynthetic membrane, and for studying the structure-function relationship of the D1 protein with respect to PSII electron transfer. Here we report the results of DNA sequence analysis of the D1 gene from four mutants not previously characterized at the molecular level, the correlation of changes in specific amino acid residues of the D1 protein with levels of resistance to the herbicides atrizine, diuron, and bromacil, and the kinetics of fluorescence decay for each mutant, which show that changes at two different amino acid residues dramatically slow PSII electron transfer. Our analyses, which identify a region of 57 amino acids of the D1 polypeptide involved in herbicide binding and which define a D1 binding niche for the second quinone acceptor, QB of PSII, provide a strong basis of support for structural and functional models of the PSII reaction center.

Amino Acid Sequence↗
PubMed1988

Chromosome assignment of the owl monkey MOS and MYC gene loci.

Southern blot hybridizations of rodent x owl monkey hybrid DNAs with human cDNA probes allowed the mapping of the MOS and MYC gene loci to owl monkey chromosome 16 of karyotype VI (2n = 49 male/50 female) and to the homologous chromosome 15 of karyotype V (2n = 46). Synteny of MOS and MYC gene loci in both man and owl monkey suggests this chromosome segment's conservation in primates, contrasting with its disruption in the mouse.

Animals↗
PubMed1987

Permissible limits of flexor digitorum profundus tendon advancement--an anatomic study.

Lacerations of the profundus tendon distal to the superficialis insertion can be treated by advancement of the proximal cut end of the tendon to its insertion. In the English-language literature, limits cited for the distance a profundus tendon can be safely advanced vary from 0.75 to 2.5 cm and appear to be based on clinical impressions. Our cadaver model suggested the degree of tendon advancement tolerable was 1 cm. A delicate balance exists in the profundus tendon system, and this should be considered when surgical advancement is contemplated.

Adult↗
PubMed1985

Variation among human 28S ribosomal RNA genes.

We report the complete 5025-base sequence of the human 28S rRNA gene. Variability within the species has been demonstrated by sequencing a variable region from six separately cloned genes. This region is one of three large subunit rRNA regions that show extreme sequence and size variation among species. The interspecies differences suggest species-specific functions for these sections, while the intraspecies heterogeneity indicates differences among ribosomes. Comparison of the human gene with a partial sequence from the chimpanzee 28S gene yields divergence rates for the two species: 0.8% for conserved regions of the gene and 3.7% for a variable region. The rapid divergence rates of variable regions in the ribosomal gene may permit answers to the question of time of separation of closely related species.

Animals↗
PubMed1985

A molecular basis for discrete size variation in human ribosomal DNA.

The tandemly repeated human ribosomal RNA (rRNA) genes contain a region of size heterogeneity that is present in the nontranscribed spacer of every individual examined. This heterogeneity has been previously examined by Southern analysis of BamHI-digested human DNA. Using a ribosomal DNA (rDNA) probe specific for the 3' end of the 28S rRNA gene, at least four discrete sizes of BamHI fragments were seen in human populations. Molecular analysis of the cloned DNA from this region reveals tandem duplication of a segment of spacer rDNA located 388 base pairs (bp) 3' to the end of the 28S ribosomal RNA gene. Five hundred fifty bp of DNA, flanked on either side by a 150-bp repeated element, is either duplicated or deleted to produce a series of spacers that differ in size by 850 bp. These duplications/deletions appear to be the product of unequal homologous exchange, mediated by the small repeated element. Thus, human rDNA fragments cloned in lambda vectors and propagated in E. coli generate the same apparent size variation seen in genomic DNA. This study suggests that unequal homologous exchange is the molecular basis for the observed length heterogeneity in the spacer rDNA and may be a common mechanism for the generation of human genetic diversity.

Bacteriophage lambda↗
PubMed1981

Structure and variation of human ribosomal DNA: molecular analysis of cloned fragments.

Eco-RI-A fragments of the human ribosomal RNA gene family from two types of tissue and three individuals were cloned in lambda vectors and compared by restriction enzyme digestion and electron microscopy. The EcoRI fragment A contains (i) 0.2 kb of the 3' end of the 18S rDNA, (ii) 2.5 kb of internal transcribed spacer and the 5.8S rDNA, and (iii) 4.6 kb of the 28S rDNA gene. All of the six cloned rDNA fragments isolated are identical by these analyses. Moreover, all contain a HincII site that is absent in about 50% of the rDNA identified by genomic blotting. Polymorphism in the nontranscribed spacer rDNA was studied in genomic blots of BamHI-digested DNA, using the 3' end of the 28S rDNA as a probe. The boundaries between the 18S rDNA, internal transcribed spacer, 28s rDNA, and external nontranscribed spacer were determined by R-loop analysis, further defining the organization of the ribosomal RNA precursor.

Bacteriophage lambda↗
PubMed1980

Further evidence for haploid gene expression during spermatogenesis: heterogeneous, poly(A)- containing RNA is synthesized post-meiotically.

Mouse testicular cells labelled in vivo with 3H-uridine for 1 hour were separated into enriched cell populations representing different stages of spermatogenesis by centrifugation in an Elutriator rotor. RNA extracted with phenol and chloroform was sized by electrophoresis on 2.4% acrylamide gels. The percentage of newly synthesized RNA which was not ribosomal RNA (or its precursors) and was not transfer RNA, was higher in early postmeiotic, as compared to late premeiotic, stages. RNA was also extracted from fractionated cells in the presence of guanidinium chloride and the proportion of total 3H-RNA-containing poly(A) sequences was determined by binding to an oligo-(dT)-cellulose column. RNA that bound in 0.5 NaCl was eluted with low salt buffer and reapplied twice more, after heating each time in DMSO to disaggregate any non-poly(A)-containing RNA. The percentage of newly synthesized RNA which contained poly(A) did not decrease in early postmeiotic, as compared to late premeiotic, stages. We suggest that at least some part of the 6-15S 3H-RNA and 3H-poly(A)-containing RNA represents mRNA(s) transcribed postmeiotically in haploid germ cells.

Animals↗