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Biomedical subjects

K M Harris

Publications and source records attributed to K M Harris.

At least 91 records · Page 5Linked to original sources
PubMed1992

The computed tomographic appearances in pulmonary artery atresia.

Isolated pulmonary artery atresia is an uncommon congenital abnormality. Plain radiography and ventilation/perfusion lung scintigraphy may suggest the diagnosis but pulmonary angiography has traditionally been recommended for confirmation. The computed tomographic (CT) appearances of four patients with isolated atresia of a pulmonary artery are described. In each case the atretic segment of the abnormal vessel could be identified. Other CT findings included reduction of volume of the involved hemithorax, increased density of the affected lung, a small hilum, and an abnormal pulmonary vascular pattern thought to be due to the collateral systemic arterial supply to the intrapulmonary branches of the atretic pulmonary artery. The diagnosis of isolated pulmonary artery atresia can be made using dynamic, contrast enhanced CT without recourse to more invasive procedures.

Adolescent↗
PubMed1992

Augmentation mammoplasty: normal and abnormal findings with mammography and US.

A retrospective review of 133 patients who had undergone augmentation mammoplasty (n = 122), reconstructive mammoplasty (n = 10), and silicone injections (n = 1) was undertaken to establish the normal appearance of various types of implants, to establish a range of normal variations (wrinkles, valves, minor bulges), and to recognize true implant complications (collapse of a saline prosthesis, leakage of silicone gel, capsular contracture, capsular calcification, and deformities). The detection and evaluation of breast parenchymal abnormalities in the presence of a radiopaque implant are more difficult, and frequently ultrasound (US) or special mammographic views in conjunction with physical examination are required. Coned-down compression spot views are suggested for asymmetric opacities or ill-defined mammographic masses, and magnification views are recommended for microcalcifications: Both should be obtained with the Eklund implant displacement technique. Tangential or other special views combined with US are best for the evaluation of palpable abnormalities and suspected silicone implant rupture.

Adult↗
PubMed1992

Three-dimensional structure of dendritic spines and synapses in rat hippocampus (CA1) at postnatal day 15 and adult ages: implications for the maturation of synaptic physiology and long-term potentiation.

It has long been hypothesized that changes in dendritic spine structure may modify the physiological properties of synapses located on them. Due to their small size, large number, and highly variable shapes, standard light microscopy of Golgi impregnations and electron microscopy (EM) of single thin sections have not proved adequate to identify most spines in a sample or to quantify their structural dimensions and composition. Here we describe a new approach, the series sample, that was developed to classify by shape and subcellular composition all of the spines and synapses in a sample of neuropil by viewing them through serial EM sections. Spines in each class are then randomly selected for serial reconstruction and measurement in three dimensions. This approach was used to assess whether structural changes in hippocampal CA1 spines could contribute to the enhanced synaptic transmission and the greater endurance of long-term potentiation (LTP) that occur with maturation. Our results show a near doubling in the total density of synapses in the neuropil and along reconstructed dendrites between postnatal day 15 (PND 15) and adult ages. However, this doubling does not occur uniformly across all spine and synapse morphologies. Thin spines, mushroom spines containing perforated postsynaptic densities (PSDs) and spine apparatuses, and branched spines increase by about four-fold in density between PND 15 and adult ages. In contrast, stubby spines decrease by more than half and no change occurs in mushroom spines with macular PSDs or in dendritic shaft synapses. The stubby spines that remain are smaller in adults than at PND 15 and the mushroom spines are larger, while no change occurs in the three-dimensional structure of thin spines. Only a few spine necks at either age are constricted or long enough to attenuate charge transfer; therefore, the doubling in synapses should mediate the enhancement of synaptic transmission that occurs with maturation. In addition, LTP is not likely to be mediated by widening of spine necks at either age. However, the constricted spine necks could serve to concentrate specific molecules at activated synapses, thereby enhancing the specificity and endurance of LTP with maturation. These results demonstrate that the new series sample method combined with three-dimensional reconstruction reveals quantitative changes in the frequency and structure of spines and synapses that are not discernable by other methods and are likely to have dramatic effects on synaptic physiology and plasticity.

Aging↗
PubMed1991

High quality private long-term care insurance: can we get there from here?

The private long-term care insurance market has undergone rapid change in the last several years. Although the quality of policies has generally improved, problems remain. Consumer protection issues include the lack of adequate inflation protection features, how activities of daily living are measured, potentially high lapse rates and lack of nonforfeiture values, how home care benefits are defined, and the appropriate loss ratio standards. The concerns of consumer and elderly advocates about the quality of private long-term care insurance have prompted congress to consider the need for federal intervention. While there are numerous approaches that the federal government could take, mandatory standards substantially higher than the current model standards of the National Association of Insurance Commissioners may prove the most effective in improving the quality of policies on a nationwide basis.

Aged↗
PubMed1991

Regulation of private long-term care insurance.

There has been a significant improvement in the quality of private long-term care insurance policies in the past five years. As the market continues to mature, national standards need to be assessed and strengthened to protect the consumer.

Aged↗
PubMed1991

Will paid home care erode informal support?

One of the main barriers to the expansion of paid home care for the chronically disabled is the fear that policymakers have that it will cause friends and relatives to curtail their informal caregiving efforts. Using the first wave of the National Long-Term Care Survey, we examine whether the amount of paid home care used by disabled elderly persons had a significant influence on the amount of informal support they were receiving. Results from a two-stage least squares regression analysis suggest that the amount of informal home care received was not significantly affected by the level of formal care. This conclusion held for subgroups of formal care users most likely to exhibit substitution: those without cognitive problems, the disabled elderly with above average income, and persons who lived alone. Even the more severely disabled elderly, who are the target of most proposals to expand paid home care, did not substitute paid care for unpaid. Thus, our study suggests that an increase in paid home care will not erode informal support.

Aged↗
PubMed1991

Mineral spirits inhalation associated with hemolysis, pulmonary edema, and ventricular fibrillation.

A previously healthy 42-year-old woman developed severe dyspnea, chest discomfort, and malaise several hours after prolonged exposure to concentrated vapors from mineral spirits. On the way to the hospital, she sustained a cardiopulmonary arrest; on arrival several minutes later, she was found to be in ventricular fibrillation and was resuscitated. Her hospital course included slowly resolving cardiac abnormalities, amnesia, noncardiogenic pulmonary edema, abrupt hemolytic anemia, sustained rhabdomyolysis, and other metabolic abnormalities. It is highly probable that this syndrome represented acute and near-lethal toxicity caused by the inhalational exposure to the petroleum distillate known as mineral spirits. It is important that physicians be aware of this syndrome in order to recognize it on presentation and to warn patients of the risk of such toxic exposure.

Administration, Inhalation↗
PubMed1990

Receiver operating characteristic analysis of chest image interpretation with conventional, laser-printed, and high-resolution workstation images.

The differences among radiologists in interpreting conventional and digitized images obtained with different radiologic procedures is an important research issue in these times of implementation and growth of the digital modalities. The authors performed a multiobserver study to determine the performance of radiologists reading posteroanterior conventional radiographs, digitized radiographs laser printed onto film, and images displayed on a high-resolution workstation (video monitor). A total of 300 images were evaluated by seven radiologists who recorded their ordinal confidence rating of the presence or absence of one or more of the following abnormalities: interstitial disease, nodule, and pneumothorax. Receiver operating characteristic analysis showed statistically significant differences for the detection of different abnormalities by individual readers. The group as a whole showed a significant reduction in observer performance for the detection of interstitial disease and pneumothorax when the laser-printed radiographs or the workstation was used rather than conventional radiographs.

Computer Systems↗
PubMed1989

CNQX (6-cyano-7-nitroquinoxaline-2,3-dione) antagonizes NMDA-evoked [3H]GABA release from cultured cortical neurons via an inhibitory action at the strychnine-insensitive glycine site.

The novel glutamate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) inhibited glutamate stimulated [3H]GABA release from cortical neurons in vitro. Kainate-induced release was blocked in a competitive fashion but N-methyl-D-aspartate (NMDA)-induced release was blocked non-competitively by CNQX. 7-Chlorokynurenate (7-CK) also inhibited NMDA evoked [3H]GABA release non-competitively, but had no effect on kainate induced release. The effects of both CNQX and 7-CK on NMDA-induced release were reversed by addition of exogenous glycine but the effects of CNQX on kainate-induced release were not altered by glycine. This suggests that both CNQX and 7-CK may interact with the glycine regulatory site of the NMDA receptor.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1989

Excitatory amino acid-evoked release of [3H]GABA from hippocampal neurons in primary culture.

We investigated the release of gamma-[2,3-3H(N)]aminobutyric acid ([3H]GABA) from hippocampal neurons in primary cell culture. [3H]GABA release was stimulated by the excitatory amino acid neurotransmitter glutamate as well as by N-methyl-D-aspartate (NMDA) and kainate. Cell depolarization induced by raising [K+]o or by veratridine also stimulated [3H]GABA release. NMDA-induced release was completely blocked by 3-((+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP+), Mg2+ and Zn2+ whereas the release induced by glutamate and kainate was much less susceptible to inhibition by these substances. Furthermore, removal of external Ca2+ inhibited NMDA-induced release, but not that induced by glutamate, kainate, veratridine or 50 mM K+. Removal of external Na+ reduced [3H]GABA release evoked by all stimuli, but to different extents. All of the excitatory amino acids tested increased [Ca2+]i within hippocampal neurons as assessed by fura-2 based microspectrofluorimetry. This increase in [Ca2+]i was completely dependent on the presence of external Ca2+. These results suggest that Ca2+-dependent and -independent forms of GABA release from hippocampal interneurons may occur. [3H]GABA release evoked by glutamate, kainate, veratridine or 50 mM K+, appeared to be mediated by the reversal of electrogenic, Na+-coupled GABA uptake. Release was inhibited by nipecotic acid, an inhibitor of the Na+-coupled GABA uptake system. However, release induced by NMDA may also include a Ca2+-dependent component.

Animals↗
PubMed1989

NMDA receptor antagonists that bind to the strychnine-insensitive glycine site and inhibit NMDA-induced Ca2+ fluxes and [3H]GABA release.

We have examined the actions of putative antagonists of the strychnine-insensitive glycine-mediated modulation of the N-methyl-D-aspartate (NMDA) receptor using [3H]MK801 binding, Ca2+ influx and [3H]GABA release assays. Kynurenic acid and HA-966 inhibited [3H]MK801 binding, NMDA and glycine induced Ca2+ influx measured using fura-2 and NMDA and glycine simulated [3H]GABA release. The effects of kynurenic acid could be partially overcome by the addition of excess glutamate and glycine, indicating limited selectivity for the glycine binding site. In addition, a component of the action of kynurenic acid was insensitive to agonist concentration, indicating a third action of kynurenic acid at high concentrations. In contrast, HA-966 was 100-fold selective for the glycine compared to the NMDA site. HA-966 only partially inhibited [3H]MK801 binding (IC50 19.7 microM), NMDA-induced Ca2+ influx and neurotransmitter release. The failure of HA-966 to completely block NMDA responses, even at high concentrations, suggests that glycine may not be an absolute requirement for the activation of NMDA receptors under these experimental conditions.

Animals↗
PubMed1989

The development of long-term potentiation in hippocampus and neocortex.

The development of long-term potentiation (LTP), an enduring alteration in synaptic efficacy following afferent activation, was examined in CA1 hippocampus and primary visual cortex of rat. Both regions show little LTP prior to postnatal day 5, demonstrate a maximal potentiated response around postnatal day 15, and a subsequent decline to adult levels. These results are discussed with respect to the underlying mechanism of action and behavioral significance of these critical-period phenomena.

Aging↗
PubMed1989

Preservation of neuronal ultrastructure in hippocampal slices using rapid microwave-enhanced fixation.

The goal of this study was to obtain fixation as rapidly as possible and to achieve preservation of neuronal ultrastructure to a depth in hippocampal slices where electrophysiological responses are optimal. This study demonstrates that perfusion quality preservation of in vitro hippocampal slices can be achieved within seconds after removal from the incubation chamber by using microwave (MW)-enhanced immersion in mixed aldehydes. The optimal method was determined to be MW irradiation of the slice for 8-11 s, to a tissue temperature of 35-50 degrees C, during immersion in fixative containing 6% glutaraldehyde and 2% paraformaldehyde. Electron microscopy of these slices revealed ultrastructural preservation that was comparable to hippocampi from animals perfused with mixed aldehyde fixative containing 2.5% glutaraldehyde and 2% paraformaldehyde. Excellent ultrastructural preservation extended to 100-175 microns from the hippocampal slice surface after MW-enhanced fixation and therefore was much deeper than the 8-20 microns that can be obtained by rapid freezing. Hippocampal slices are routinely maintained in vitro for electrophysiological or pharmacological studies. This method of MW-enhanced fixation preserves tissue within seconds after removal from incubation, and should provide good preservation of the hippocampal anatomy that might be associated with in vitro physiology.

Aldehydes↗
PubMed1989

The mammographic features of the postlumpectomy, postirradiation breast.

Lumpectomy with radiation therapy is becoming widely accepted as an alternative treatment for breast carcinoma in place of radical mastectomy. This article illustrates the spectrum of mammographic changes seen at various intervals after lumpectomy with irradiation to help the mammographer distinguish postoperative scar from a recurrent carcinoma.

Breast Neoplasms↗