Biomedical subjects

E Grant

Publications and source records attributed to E Grant.

At least 19 recordsLinked to original sources

PubMed1992

Mechanism of magainin 2a induced permeabilization of phospholipid vesicles.

The magainins, peptide antibiotics secreted by the frog Xenopus laevis, have previously been shown to permeabilize phospholipid vesicles. To elucidate the mechanism of permeabilization, we have conducted detailed kinetic studies of magainin 2 amide (mgn2a)-induced release of 6-carboxyfluorescein from vesicles of phosphatidylserine. The results show that dye release occurs in (at least) two stages--an initial rapid phase, with t1/2 approximately 3 s, followed by a much slower phase that approaches zero leakage rate before all the dye is released. Light-scattering studies showed that mgn2a does not cause gross changes in vesicle structure. The peptide was found to rapidly equilibrate between vesicles; this was demonstrated by determining a binding isotherm for the peptide-lipid interaction, and by showing that addition of unloaded vesicles rapidly quenches peptide-induced leakage from loaded vesicles. Transient dye release in the presence of an equilibrating peptide can be explained in two ways: (1) the peptide exists only transiently in an active form; (2) the vesicles are only transiently leaky. Preincubation of mgn2a at assay concentrations in buffer alone or with unloaded vesicles did not inactivate the peptide. Therefore, rapid leakage is probably due to transient destabilization of the vesicle upon addition of mgn2a.

Animals↗

PubMed1992

Interleukin 4 induces the maturation of idiotype-specific regulatory B cell populations.

CD5+ B cells have been shown to be disproportionately associated with autoimmune diseases and transformation. In many cases, their apparent ability to bypass self-tolerance is manifested by the production of autoantibodies. These observations, plus the hypothesis that CD5+ B cells represent a distinct B cell lineage, encourage studies into the conditions and factors that influence their development. In the present study, we employed a well-established assay for murine CD5+ B cell function, i.e., their ability to augment the responses of IgHb-linked idiotypic determinants on anti-(4-hydroxy-3-nitrophenyl) acetyl (NP) antibody (Nbb) idiotype-bearing CD5- B cells to a T-independent antigen, together with multiple methods of cell surface phenotyping, to evaluate the potential for interleukin (IL) 4 to effect maturation of CD5+ B cells, CD5+, IgM+, Thy-1-, and NPb idiotype-specific cells panned on antibody-coated petri dishes or sorted by flow cytometry from spleen were capable of augmenting NPb idiotypic responses of NP-KLH-primed responder cells to NP-Ficoll. Splenic B cell populations depleted of CD5+ B cells failed to affect idiotype expression even after 2 days in culture, a time when a small percentage of CD5+ B cells appeared to be regenerated. However, idiotype-specific regulatory activity could be restored in CD5- splenic B cell populations by culture for 2 days with recombinant IL-4. Cells responsible for idiotype-specific regulatory activity after culture with IL-4 were in fact CD5+, IgM+, and Thy-1.2- B cells, demonstrating that IL-4 can drive the functional, if not the phenotypic, maturation of splenic B cells associated with the CD5+ B cell lineage. The results illustrate one possible mechanism by which T cells could control the maturation of cells belonging to the CD5+ B cell lineage.

Animals↗

PubMed1991

The effects of selenium deficiency on hepatic type-I iodothyronine deiodinase and protein disulphide-isomerase assessed by activity measurements and affinity labelling.

We determined protein disulphide-isomerase (PDI) and iodothyronine deiodinase (ID-I) activities in liver homogenates from rats subjected to selenium (Se) and/or iodine deficiencies and food restriction. Additionally, the effects of propylthiouracil (PTU) on the enzymes were studied in vivo and in vitro. Selenium deficiency markedly inhibited ID-I activity, but had no significant effects on PDI. Iodine deficiency resulted in a 1.6-fold stimulation in ID-I and a 1.2-fold stimulation in PDI activities. ID-I was much more sensitive than PDI to the inhibitory effects of PTU both in vitro and in vivo. By using a 3,3',5'-tri[125I]iodothyronine affinity label, two major protein bands were identified when hepatic microsomal fractions from Se-sufficient rats were subjected to SDS/PAGE and autoradiography. These bands had molecular masses of 55 and 27.5 kDa, which are similar to those of PDI and ID-I respectively. Selenium deficiency resulted in the loss of the 27.5 kDa band, but did not affect the intensity of the 55 kDa band. These results are consistent with the changes in PDI and ID-I enzyme activities. Previous studies have shown that 75Se may be incorporated in vivo into the 27.5 kDa protein band. This, taken together with our observation that Se is required for the expression of ID-I and the 27.5 kDa protein band, strongly suggests that ID-I is a selenoprotein.

Affinity Labels↗

PubMed1990

Brief screening tests versus clinical staging in senile dementia of the Alzheimer type.

Several brief screening tests of cognitive function were compared with a reliable and valid global rating of the presence and severity of senile dementia of the Alzheimer type, the Washington University Clinical Dementia Rating (CDR). The six-item Short Blessed Test, the Short Portable Mental Status Questionnaire, the 26-item Blessed Information-Memory-Concentration Test, the Blessed Dementia Scale, and the Blessed Dementia Scale-Cognitive were able to discern both the presence of dementia and its severity. The six-item Short Blessed Test is preferred as a screening test because of its brevity, administration to the subject only, inclusion of a learning task, reliability, and neuropathologic validity. Evidence is presented for the convergent validity of the Initial Subject Protocol, used to derive the Clinical Dementia Rating.

Aged↗

PubMed1990

Assurance of consistent peak-velocity measurements with a variety of duplex Doppler instruments.

To assess the need for quality control when measuring peak velocities with Doppler ultrasonography, 17 duplex Doppler instruments from six manufacturers were compared by using a flow phantom that had been calibrated for peak velocities ranging from 23 to 75 cm/sec. Variations in peak-velocity measurements among machines averaged 23% when tested at the same flow rate with a Doppler flow phantom, indicating that scientific articles that document peak velocities for various disease processes should be accompanied by equipment calibration data. Doppler string and flow phantoms were compared, and each was found to have deficiencies. Techniques for quality assurance procedures for Doppler measurements are given that should achieve consistent peak-velocity measurements on serial scans of patients undergoing treatment for vascular conditions.

Blood Flow Velocity↗

PubMed1989

Reliability of clinical nurse specialists in the staging of dementia.

We studied the reliability of master's-prepared clinical nurse specialists for the identification and staging of dementia, using videotapes of physician assessments of both healthy older persons and those with senile dementia of the Alzheimer type. The Washington University (St Louis, Mo) Clinical Dementia Rating system was the staging instrument. The results from three nurses, each reviewing 25 videotaped assessments, indicate that agreement is high between clinical nurse specialists and physicians for the presence and severity of dementia (kappa = .75). This study suggests that clinical nurse specialists can use the Clinical Dementia Rating scale effectively, and thus reliably identify and stage dementia.

Aged↗

PubMed1987

Recurrent cerebral ischemia and mitral valve vegetation in a patient with antiphospholipid antibodies.

A 37-year-old woman presented with a history of acute loss of vision in her left eye and a history of recurrent transient ischemic attacks. Subsequent investigations revealed a prolonged PTT. The lupus anticoagulant and anticardiolipin antibodies (aCL) were identified in her serum. A cardiac murmur was heard and echocardiography demonstrated a mass on the mitral valve. Extensive studies for infection were negative. Cardioembolic phenomena were considered a possible cause of her cerebral ischemic events. The occurrence of nonbacterial endocardial verrucae is well described in systemic lupus erythematosus. The pathogenesis of this lesion remains speculative, however, its occurrence in our patient, with a lupus anticoagulant and aCL suggests a possible association. The clinical manifestations of thrombosis in patients with antiphospholipid antibodies are varied, and may include the development of thrombotic endocardial lesions.

Adult↗

PubMed1984