Biomedical subjects
M H Johnson
Publications and source records attributed to M H Johnson.
Neurofibroma manifested by spinal subarachnoid hemorrhage.
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Assessment of diabetes care by medical record review. The Indian Health Service model.
OBJECTIVE: To evaluate the adherence to minimum standards for diabetes care in multiple primary-care facilities using a uniform system of medical record review. RESEARCH DESIGN AND METHODS: In 1986, the Indian Health Service (IHS) developed diabetes care standards and an assessment process to evaluate adherence to those standards using medical record review. We review our assessment method and results for 1992. Charts were selected in a systematic random fashion from 138 participating facilities. Trained professional staff reviewed patient charts, using a uniform set of definitions. A weighted rate of adherence was constructed for each item. RESULTS: Medical record reviews were conducted on 6,959 charts selected from 40,118 diabetic patients. High rates of adherence (> 70%) were noted for blood pressure and weight measurements at each visit, blood sugar determinations at each visit, annual laboratory screening tests, electrocardiogram at baseline, and adult immunizations. Lower rates of adherence (< or = 50%) were noted for annual eye, foot, and dental examinations. CONCLUSIONS: IHS rates of adherence are similar to rates obtained from medical record reviews and computerized billing data, but are less than rates obtained by provider self-report. Medical record review, using uniform definitions and inexpensive software for data entry and reports, can easily be implemented in multiple primary-care settings. Uniformity of data definition and collection facilitates the aggregation of the data and comparison over time and among facilities. This medical record review system, although labor intensive, can be easily adopted in a variety of primary-care settings for quality improvement activities, program planning, and evaluation.
Iontophoretically applied potassium ions as an experimental pain stimulus for investigating pain mechanisms.
The present study investigated the psychophysical characteristics of potassium iontophoresis and its suitability as an experimental pain stimulus. Experiment 1 investigated the optimal duration of the pain stimulus for reliable reporting across repeated trials and whether the relationship between stimulus and subject response was linear, logarithmic, or a power function. In Experiment 2, the optimal interstimulus interval (ISI) was determined for reliable pain reporting, and stimulus history effects, both in terms of session effects and the effects of immediately preceding stimuli, were evaluated. In Experiment 3, potassium iontophoresis was compared with a sodium iontophoresis control. Linear functions described the stimulus-pain relationship best. No significant differences in the goodness-of-fit coefficients of determination, correlations, or coefficients of variation were found for the stimulus durations of 1, 2, and 4 sec. Significant stimulus history effects were found across a session, with adaptation and enhancement of responding for low- and moderate-intensity stimuli, respectively. The effects of the immediately preceding stimuli were suppression or enhancement of pain response, depending on the ISI, the preceding stimulus intensity, and the present stimulus intensity. Potassium iontophoresis was a significantly more effective pain stimulus than was sodium iontophoresis. It was concluded that potassium iontophoresis is a convenient and reliable experimental pain stimulus, which can be presented rapidly and repeatedly with minimal loss in consistency of subject pain report. Potassium iontophoresis provides a tool for investigating the neural modulation of pain in the relative absence of inflammation processes and tissue damage.
Lesions of the craniovertebral junction.
There has been a renewed interest in the normal and pathologic lesions of the CVJ with the growth of MR imaging. A host of pathologies, both congenital and acquired, may manifest at the CVJ. Basilar invagination and basilar impression and their impact on the CMJ are readily diagnosed using a variety of noninvasive imaging modalities. Evaluation of the CVJ on cranial and cervical MR examinations should be a routine part of image interpretation.
Cell-cycle control of a large-conductance K+ channel in mouse early embryos.
There have been few investigations into the role of ion channels in mammalian early embryonic development, despite studies showing that changes in ion channel activity accompany the early embryonic development of non-mammalian species and the proliferation of mammalian cells. Here we report that a large-conductance, voltage-activated K+ channel is active in unfertilized mouse oocytes but is rarely observed in later embryos. The channel activity is linked to the cell cycle, being active throughout M and G1 phases, and switching off during the G1-to-S transition. These changes in channel activity are accompanied by corresponding shifts in membrane potential. Inactivation of the channel during S/G2 can be prevented by exposing the oocytes to dibutyryl cyclic AMP or forskolin, an activator of adenylyl cyclase. Inhibition of protein synthesis with puromycin did not prevent inactivation of the channel at the end of G1 or its subsequent reactivation at the end of G2, indicating that the channel activity is not regulated by mitosis-promoting factor or cyclins.
Assessment of the cellular DNA content of whole mounted mouse and human oocytes and of blastomeres containing single or multiple nuclei.
The nuclear DNA content of intact, live or fixed, human and mouse oocytes and blastomeres has been measured rapidly and reliably. Chromosomal DNA has been stained with DAPI, the fluorescent emission from which has been measured photocytometrically. In vitro fertilised mouse oocytes and embryos at various stages of development were assessed for their DNA content. The mean values of 1C, 2C and 4C DNA content were clearly different, and it was possible to assign correctly individual values for DNA content to each class with 92%, 61% and 81% confidence respectively. Maintaining the cells as whole mounts allowed other morphological and structural features to be examined. When formation of multiple micronuclei was induced in mouse oocytes by their insemination in the presence of nocodazole, the additive signal from all the micronuclei in one zygote was equivalent to the expected DNA content. Application to early human blastomeres of this photocytometric technique for measurement of the total cellular DNA content revealed that multinucleated blastomeres contained 2C to 4C DNA levels, consistent with a diploid DNA content.
Staurosporine advances interblastomeric flattening of the mouse embryo.
Staurosporine, an inhibitor of protein kinase activity, causes premature intercellular flattening of blastomeres but does not induce their premature polarisation. The flattening induced is calcium dependent, is reversed transiently at mitosis and requires the continuing presence of the drug. Staurosporine also blocks the decompacting effect of phorbol ester on 8-cell embryos.
Cell surface localisation and stability of uvomorulin during early mouse development.
We have examined immunocytochemically the subcellular distribution of the cell adhesion molecule uvomorulin in cleavage stage mouse embryos using conventional and confocal microscopy, under a range of detergent extraction and fixation regimes. Only traces of uvomorulin were detectable on the surface of unfertilised oocytes, whereas between 6 and 11 h after activation detergent-resistant surface expression was evident. This shift correlates with previously demonstrated changes in the pattern of synthesis and accumulation of uvomorulin from precursor state in unfertilised oocytes to mature protein after fertilisation. Embryos at subsequent stages up to the 8-cell stage exhibited a uniform distribution of uvomorulin on free surfaces and its concentration in regions of contact between blastomeres. At the 8-cell stage, during compaction, there was increased intercellular adhesion with concomitant accumulation of uvomorulin at intercellular contacts, whilst free surface uvomorulin was reduced and became relatively more susceptible to detergent extraction. When compact 8-cell embryos were decompacted in calcium-free medium, uvomorulin at contacts decreased while free surface and cytoplasmic staining increased. Blastomeres disaggregated from 4- and 8-cell embryos showed traces or 'footprints' of anti-uvomorulin staining in regions previously in apposition. These footprints disappeared over 45-60 min, during which time uvomorulin distribution became uniform. Possible mechanisms underlying the rearrangements which take place both at fertilisation and during compaction and experimental decompaction are discussed.
Identification of the renal erythropoietin-producing cells using transgenic mice.
Regulation of erythropoietin production by the kidneys is central to the control of erythropoiesis. Uncertainty about the identity of the renal cells involved has been a major obstacle to understanding this mechanism. We have used sequence from the mouse erythropoietin locus to direct expression of a marker gene, SV40 T antigen, to these cells in transgenic mice. The transgenic constructs contained an oligonucleotide marker (Epo-M) or SV40 sequence (Epo-TAg) in the 5' untranslated region of the mouse erythropoietin gene, flanked on each side by 9 and 7.5 kb of DNA from the mouse erythropoietin locus. Anemia-inducible expression of Epo-M and Epo-TAg was observed in the kidney. In one of thirteen lines, homologous integration of Epo-TAg into the mouse erythropoietin locus occurred. In transgenic mice bearing Epo-TAg at homologous and heterologous insertion sites, renal expression was restricted to a population of cells in the interstitium of the cortex and outer medulla. Immunohistochemical characterization by light and electron microscopy shows that these are the fibroblast-like type I interstitial cells.
Use of fetal bovine serum substitutes for the protection of the mouse zona pellucida against hardening during cryoprotectant addition.
The addition of 20% fetal bovine serum (FBS) to media used for mouse oocyte cryopreservation prevents hardening of the zona pellucida that otherwise can occur due to premature release of cortical granule contents (George et al., Hum. Reprod., 7, 401-412, 1992). Protection of human oocytes would ideally be achieved by using a human macromolecular source or a more defined bovine source than total FBS. Here we investigate whether FBS can be replaced by human serum, human cord serum, human serum albumin or fetuin, the major protein component of FBS. Only fetuin was found to be effective.
Are failed-fertilized human oocytes useful?
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Cytoskeletal organization and zona sensitivity to digestion by chymotrypsin of frozen-thawed mouse oocytes.
Mouse oocyte-cumulus masses were added to 1.5 dimethyl sulphoxide (DMSO) + 20% fetal bovine serum (FBS) that had been precooled at +4 degrees C, were frozen by slow cooling to an intermediate temperature of -60 degrees C before being plunged into liquid nitrogen at -196 degrees C, subjected to a controlled thaw, expelled into 1.5 M DMSO + FBS at 4 degrees C, and then washed in medium + FBS at 37 degrees C. Of 7733 oocytes treated, 78.4% were viable (controls; no treatment: 94.2% of 2764 oocytes; cryoprotectant only: 92.2% of 2991 oocytes). The oocyte losses were not due to complete loss of all oocytes from some straws or mice, since analysis of individual straws containing oocytes from a single mouse revealed considerable inter-straw/mouse variation. Amongst surviving oocytes, no significant differences between frozen and control oocytes in spindle, chromosomal or microfilament organization were recorded. Two significant differences were observed: (i) fewer frozen-thawed oocytes had zonae resistant to chymotrypsin digestion, and (ii) spindle organization in control oocytes, but not frozen-thawed oocytes, was improved by 3 h incubation at 37 degrees C. More of the abnormal than the normal frozen-thawed and control oocytes were surrounded by zonae which were resistant to digestion by chymotrypsin.
Fertilisation and thimerosal stimulate similar calcium spiking patterns in mouse oocytes but by separate mechanisms.
Exposure of freshly ovulated mouse oocytes to a fertilising spermatozoon, thimerosal, Sr2+ or acetylcholine induced similar Ca2+ spiking responses. We propose that each of the four agents reduces the threshold for Ca2+ release from internal stores, but by different mechanisms. All agents except thimerosal stimulated oocyte activation, but thimerosal caused dissassembly of the meiotic spindle and thus prevented progress into interphase. Dithiothreitol (DTT) completely blocked and reversed the spiking responses induced by thimerosal, but facilitated and accelerated those induced by spermatozoa, Sr2+ and acetylcholine. The stimulatory effect of DTT was not simply a consequence of progress into interphase, but was attributable, at least in part, to an enhancement of divalent cation entry, as measured by Mn2+ quench analysis of fura-2 in both fertilised and unfertilised oocytes. Possible mechanisms by which DTT might achieve its effects are discussed.
Prolonged neurological disability following OKT3 therapy for acute renal transplant rejection.
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Chemotherapy: thoughts and images of patients with cancer.
Cognitive therapists believe that an individual's emotional reaction to a stressful situation is influenced by his or her perception of that situation. This article reports the findings of a cross-sectional survey comparing thought and image patterns in patients with cancer receiving first-time chemotherapy with patients receiving subsequent treatments. The 30 patients in each sample listed their thoughts and images before, during, and after chemotherapy. In both samples, a higher percentage of positively rated self-talk units were expressed; most negative thoughts took place before the chemotherapy. Qualitative content analysis revealed that, in first-time chemotherapy recipients, the most frequently reported thought categories were questions and concerns about chemotherapy, positive evaluations of treatment, positive coping, and negative feelings. In the subsequent-treatment recipients, they were positive coping, physiologic reactions, hope, and positive evaluations of treatment. Nursing implications and future research directions also are discussed.
The effect of the neurotoxin DSP4 on the development of a predisposition in the domestic chick.
Under certain conditions, dark-reared chicks preferentially approach objects resembling conspecifics. In the current study we investigated the effect of the catecholaminergic neurotoxin DSP4 on this predisposition. After hatching, chicks received an intraperitoneal injection of either DSP4 or vehicle (controls). The chicks were individually placed in running wheels for 2 x 1 hr, 24 hr before testing. The chicks were maintained in darkness until given a preference test, which involved the simultaneous presentation of an illuminated red box and a stuffed fowl at 36, 48, 60, 66, or 72 hr after hatching. The approach of each chick toward the two objects was recorded over 5 min and a preference score calculated. Control chicks placed in the running wheels at 24 and 36 hr posthatch and tested 24 hr later showed a significant preference for the fowl compared to the red box. In contrast, DSP4-treated chicks did not show such a preference at corresponding ages, but did express a greater preference for the fowl when placed in the running wheels at 42 and 48 hr posthatch and tested 24 hr later. These results suggest that experience of the running wheel or of associated factors, e.g., handling, must occur during a restricted period of time to influence the emergence of the predisposition to approach the stuffed fowl. DSP4 treatment delays the onset of this period.
Use of fetal bovine serum to protect against zona hardening during preparation of mouse oocytes for cryopreservation.
Addition of 20% fetal bovine serum (FBS) to media used for cryopreservation does not reduce the premature release of cortical granules but does prevent their action on the zona pellucida and thereby prevents zona hardening. In this paper, it is shown that the washing period required for removal of FBS is less than 12 min for cumulus-free oocytes and between 150 and 170 min for cumulus-intact oocytes. When these washing periods are observed after exposure of oocytes to the cryoprotectant dimethylsulphoxide (DMSO; 1.5 M) in the presence of 20% FBS, a subsequent exposure to calcium ionophore A23187 or a second exposure to 1.5 M DMSO both lead to zona hardening. This result suggests that sufficient cortical granules remain to elicit a block to polyspermy at fertilization. Oocytes, which had been exposed to DMSO and FBS and then washed free of both, were fertilized in vitro; the incidence of polyspermy was not found to be elevated over the level found in controls.