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Biomedical subjects

J L Smith

Publications and source records attributed to J L Smith.

At least 199 records · Page 11Linked to original sources
PubMed1995

Assessment of intracranial primary collaterals using transcranial color-coded real-time sonography.

Transcranial color-coded sonography (TCCS) was used to assess primary willisian collaterals in 100 patients with extracranial internal carotid artery (ICA) stenosis. Their importance was determined during carotid endarterectomy (CEA) by transcranial Doppler measurement of blood flow velocity in the ipsilateral middle cerebral artery (MCAV) before and after carotid clamping. All patients had unilateral ICA disease of at least 60% stenosis. Twenty-nine ICAs (14.5%) were occluded, 70 vessels (35%) were stenosed by 80 to 99%, 43 vessels (21.5%) were stenosed by 60 to 79%, and 53 ICAs had stenosis of less than 60%. Temporal hyperostosis precluded TCCS in 15 patients (15%). Anterior cerebral/communicating artery collaterals were detected in 40 patients (49%) and posterior cerebral/communicating artery collaterals were detected in 22 patients (27%). No patients with ICA stenosis of less than 80% had established collateral pathways. Patients with willisian collaterals showed higher postclamp MCAVs as a proportion of the preclamp value during CEA (72% [62-81]; median with 95% confidence interval) than did those without primary collaterals (46% [34-58], p = 0.02). TCCS allows noninvasive assessment of intracranial primary collaterals whose functional importance is recognized during abrupt hemodynamic challenge. It may determine which patients are at greatest risk of ischemia during cerebral revascularization.

Aged↗
PubMed1995

Unexpected motor patterns for hindlimb muscles during slope walking in the cat.

1. Hindlimb kinematics and motor patterns were assessed from high-speed ciné film synchronized with electromyographic (EMG) data from cats trained to walk on a walkway placed at four grades (25, 50, 75, and 100%). 2. Flexor muscles of the hip (iliopsoas) and ankle (tibialis anterior) had similar activity patterns for the swing phase of up- and down-slope walking; both flexor muscles also had stance-related activity during down-slope walking and this was unexpected. Extensor muscles of the hip (anterior biceps femoris and anterior semimembranosus), knee [vastus lateralis (VL)], and ankle [lateral gastrocnemius (LG)] were active during the stance phase of up-slope walking. The VL and LG activity was reduced in duration during stance of down-slope walking and centered around paw contact. Hip extensors, however, were totally inactive during stance of down-slope walking, and this was not expected. 3. Flexor muscles at the hip and ankle (not extensor muscles) dominated the stance phase of down-slope walking, especially at the steeper slopes. This switch in motor patterns may be required to counterbalance external forces that produced extension at the hip and ankle joints during the stance phase of down-slope walking. Neural mechanisms for programming stance-related activity of flexor muscles are discussed.

Animals↗
PubMed1995

Interpretation of embolic phenomena during carotid endarterectomy.

BACKGROUND AND PURPOSE: Air and particulate emboli are a major source of morbidity during carotid endarterectomy (CEA); however, amplitude overload and poor time resolution have restricted the ability of transcranial Doppler ultrasound to differentiate between the two. METHODS: We have now overcome these two limitations by (1) rerouting embolic signals away from the audio frequency amplifier to avoid amplitude overload and (2) substituting the Wigner distribution function for the fast Fourier transform to improve time and frequency resolution. Thus, we can now accurately determine embolic duration and embolic velocity, the product of which is the sample volume length (SVL). This measurement represents the physical distance over which an embolic signal can be detected. The underlying hypothesis was that air reflected more ultrasound and would therefore be detected over a greater SVL. RESULTS: The median SVL (interquartile range) for 75 in vitro air emboli was 1.97 cm (range, 1.70 to 2.35) compared with 0.27 cm (range, 0.16 to 0.43) for 185 particulate emboli detected during the dissection phase of CEA. Off-line analysis on an additional 560 embolic signals detected during different phases of CEA suggested that 46 of 143 (32%) of emboli immediately after shunt insertion were particulate, as were 19 of 33 (58%) occurring during shunting, 28 of 78 (36%) after restoration of flow in the external carotid artery, 23 of 251 (9%) after restoration of flow in the internal carotid artery, and 55 of 55 (100%) of those emboli detected during the early recovery phase. CONCLUSIONS: This development provides objective physical criteria upon which embolus characterization (particulate/air) can be based. This could have major implications for future patient monitoring with respect to modification of surgical technique and pharmacological intervention.

Embolism, Air↗
PubMed1995

Heritability of ascites and the ratio of right to total ventricle weight in broiler breeder male lines.

The objectives of this study were to induce ascites in three pure male line populations by subjecting them to cold stress, and to calculate heritability estimates for ascites (ASCITES) and the ratio of right to total ventricle weight (RATIO) in these populations under cold stress. Data were collected during the winter of 1993 to 1994 from 3,436 cockerels representing three commercial broiler breeder male lines. The male lines used in this study were characterized by: rapid growth rate and good feed efficiency (RG), moderate growth, good conformation, and excellent livability (MG), and maximum white meat yield and rapid growth (YD). Birds were cold stressed and euthanatized at 8 wk of age. Ratios of right to total ventricle weight and ascites (birds with fluid in the abdominal cavity) were recorded on every bird. Line means for the incidence of ascites were 17.5, 18.7, and 33.5% for RG, MG, and YD, respectively. Lines RG and MG did not differ from each other for ascites, but both were less than YD (P < .05). Means and standard deviations for the ratio of right to total ventricle weight (RATIO) were .299 +/- 0.9, .297 +/- .08, and .294 +/- .09 for RG, MG, and YD, respectively. Line means for RATIO did not differ. Heritability estimates of RATIO were .21 +/- .09, .21 +/- .09, and .27 +/- .08 for RG, MG, and YD, respectively; and heritabilities of ascites were .36 +/- .10, .11 +/- .08, and .44 +/- .09, respectively. Phenotypic correlations of ASCITES with RATIO were .54, .43, and .50 in RG, MG, and YD and genetic correlations of ASCITES with RATIO were .69 +/- .13, .46 +/- .33, and .78 +/- .10 in RG, MG, and YD, respectively.

Animals↗
PubMed1995

Developmental expression of elements of hepatic cholesterol metabolism in the rat.

The expression of several key enzymes and receptors of rat hepatic cholesterol metabolism was studied during development. Among major findings were: acyl coenzyme A:cholesterol acyltransferase, the cholesteryl ester hydrolases, cholesterol-7 alpha-hydroxylase and the alpha 2-macroglobulin receptor (LRP) were very low in fetal livers, but all were induced shortly before birth, suggesting that these elements are important for extrauterine life. Although the other elements continued to increase, by day 6 of postnatal life, cholesterol-7 alpha-hydroxylase had reached undetectable levels. It reappeared by day 12 of suckling, placing it in the group of late-appearing activities necessary for the fully mature hepatic phenotype. Changes in acyl coenzyme A:cholesterol acyltransferase activity appeared due predominantly to changes in amount of active protein. The cholesteryl ester hydrolase (CEH) activities all showed different developmental patterns, suggesting that each was a unique activity. The bile salt-dependent CEH activity was much higher in the suckling period than in the adult where it was almost undetectable, suggesting that this CEH may have its major importance in the suckling period of development. Low density lipoprotein receptors exhibited a pattern very different from that of the alpha 2-macroglobulin receptors and did not show consistent correlation with any other elements. At some developmental time points, the relationships amongst the elements differed significantly from the adult pattern. These studies provide for the first time an integrated picture of developmental expression of key elements of hepatic cholesterol metabolism and set the stage for further studies on their modes of regulation.

Animals↗
PubMed1995

Simultaneous, multiple cranial neuropathies in diabetes mellitus.

Cranial mononeuropathies, particularly ophthalmoplegia and facial palsy, are common entities in the diabetic population. Simultaneous multiple cranial neuropathies due to diabetes are much less common, however. We present three patients with this entity.

Abducens Nerve↗
PubMed1994

Automated HLA-B27 testing using the FACSPrep/FACScan system.

Tissue typing can help in the diagnosis of the seronegative arthropathy ankylosing spondylitis. Using an automatic sample preparation system and flow cytometry (FACSPrep/FACScan) we have developed a test for HLA-B27 screening using whole blood which is both rapid, reproducible, and permits simultaneous screening of large numbers of samples. We have used both indirect (248 cases) and direct (126 cases) monoclonal antibody staining techniques. Results were assessed using median channel shift (CS) from the negative control and relative fluorescence intensity. There is known cross-reactivity between HLA-B27 and HLA-B7 with the monoclonal antibody (MoAb) HLA-ABC-m3. Using this antibody and indirect staining, HLA-B7 samples had a significantly lower CS value than HLA-B27 samples. In 60% of these cases there was a clear distinction between HLA-B27 and HLA-B7. All HLA-B27 and HLA-B7 negative samples had a CS of 0 (P < 0.001). Using direct dual staining with CD3 and HLA-B27, all HLA-B27 and HLA-B7 negative samples had a low CS value (15 maximum), HLA-B7 samples had an intermediate CS value (20-85), and HLA-B27 samples had the highest CS values (70 upward). This system permits large scale rapid negative screening of samples with the elimination of over 60% as negatives (CS < 15). Limitations as a definitive test for HLA-B27 are due to MoAb cross-reactivity with HLA-B7 which necessitates other confirmatory techniques. The substitution of the HLA-ABC-m3 with the recently available HLA-B27 specific MoAb FD705 would substantially increase the value of this technique for routine HLA-B27 typing.

Antibodies, Monoclonal↗
PubMed1994

Structure of the allosteric regulatory enzyme of purine biosynthesis.

Multi-wavelength anomalous diffraction (MAD) has been used to determine the structure of the regulatory enzyme of de novo synthesis of purine nucleotides, glutamine 5-phosphoribosyl-1-pyrophosphate (PRPP) amidotransferase, from Bacillus subtilis. This allosteric enzyme, a 200-kilodalton tetramer, is subject to end product regulation by purine nucleotides. The metalloenzyme from B. subtilis is a paradigm for the higher eukaryotic enzymes, which have been refractory to isolation in stable form. The two folding domains of the polypeptide are correlated with functional domains for glutamine binding and for transfer of ammonia to the substrate PRPP. Eight molecules of the feedback inhibitor adenosine monophosphate (AMP) are bound to the tetrameric enzyme in two types of binding sites: the PRPP catalytic site of each subunit and an unusual regulatory site that is immediately adjacent to each active site but is between subunits. An oxygen-sensitive [4Fe-4S] cluster in each subunit is proposed to regulate protein turnover in vivo and is distant from the catalytic site. Oxygen sensitivity of the cluster is diminished by AMP, which blocks a channel through the protein to the cluster. The structure is representative of both glutamine amidotransferases and phosphoribosyltransferases.

Adenosine Monophosphate↗
PubMed1994

Phospholipase D activation in fibroblast membranes by the alpha and beta isoforms of protein kinase C.

The regulation of phosphatidylcholine-hydrolyzing phospholipase D (PLD) by protein kinase C (PRC) in membranes of Chinese hamster lung fibroblasts (CCL39) was studied using conventional PKC isoforms alpha, beta and gamma isolated from rat brain and recombinant PKC isoforms. Cells were incubated with [14C]choline to label endogenous phosphatidylcholine before membranes were prepared and assayed for release of [14C]choline. PKC alpha was the most potent activator of PLD, producing a maximal effect at approximately 0.1 microgram/ml. PKC beta also stimulated PLD but was less potent and less efficacious, whereas PKC gamma was ineffective. Stimulation required addition of a PKC activator, but the isoform specificity was the same whether phorbol 12-myristate 13-acetate (PMA) or Ca2+ was used. Recombinant Ca(2+)-independent PKC isoforms delta, epsilon, and zeta failed to stimulate PLD, but recombinant PKC beta 1 stimulated PLD in a manner similar to the purified brain PKC beta. Immunoblot analysis of the soluble fraction of CCL 39 fibroblasts detected only the alpha and zeta isoforms of PKC. The results suggest that PKC alpha and beta are activators of PLD and that PKC alpha is responsible for the activation in these fibroblasts.

Animals↗
PubMed1994

Quantitative analyses of neuroepithelial cell shapes during bending of the mouse neural plate.

Despite a wealth of information about cell behaviors contributing to neurulation in chick embryos, similar behaviors in mouse embryos have yet to be well characterized. This study examines cell behaviors occurring during bending of the mouse neural plate, in particular, qualitative and quantitative changes in neuroepithelial cell shape. Our current results demonstrate that in mouse embryos 1) the median hinge point (MHP), a localized region of neural plate that becomes anchored to the underlying prechordal plate mesoderm or notochord/notochordal plate and forms a midline longitudinal furrow around which folding of the remaining neural plate (i.e., the part of the neural plate not involved in MHP formation) occurs, develops during stages of neural fold elevation; 2) the MHP is enriched with wedge-shaped neuroepithelial cells but has significantly fewer spindle-shaped, inverted wedge-shaped, and globular neuroepithelial cells than do the adjacent paired lateral areas of the neuroepithelium (L); and 3) each L is enriched with spindle-shaped, inverted wedge-shaped, and globular neuroepithelial cells but has significantly fewer wedge-shaped neuroepithelial cells than does the MHP. Thus wedging of neuroepithelial cells occurs during bending of the mouse neural plate and is localized to the MHP during neural fold elevation. Similarly, previous studies in the chick have shown that neuroepithelial cells become wedge shaped during bending of the neural plate and that such cell wedging is localized to the MHP during neural fold elevation. Such studies also have shed light on the roles of MHP formation and localized wedging of neuroepithelial cells within the MHP in the chick; however, such roles have yet to be elucidated in the mouse.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Binding of purine nucleotides to two regulatory sites results in synergistic feedback inhibition of glutamine 5-phosphoribosylpyrophosphate amidotransferase.

Glutamine 5-phosphoribosylpyrophosphate amidotransferase from Escherichia coli is subject to synergistic feedback regulation by adenine and guanine nucleotides. Inhibition assays and equilibrium binding measurements have established that synergistic inhibition by AMP and GMP results from synergistic binding to two sites/enzyme subunit in the homotetramer. Although each nucleotide can bind to both sites, analyses of the wild type and mutant enzymes indicate that binding of GMP to an A (allosteric) site and AMP to a proximal C (catalytic) site are necessary for synergistic inhibition. K326Q and P410W amino acid replacements result in decreased binding affinity for GMP and AMP and lead to corresponding reductions in feedback inhibition. The K326Q A site mutation results not only in decreased affinity of GMP for the mutant A site but also has an adverse effect on AMP affinity for the C site. Similarly, the P410W C site mutation has a detrimental effect on binding of AMP to the mutant C site and also on affinity of GMP to the A site. The fact that a mutation in one site affects binding of nucleotides to both sites provides further evidence for synergistic binding of nucleotides.

Adenosine Monophosphate↗
PubMed1994

Crystal structure of chloroplast cytochrome f reveals a novel cytochrome fold and unexpected heme ligation.

BACKGROUND: Cytochrome f is the high potential electron acceptor of the chloroplast cytochrome b6f complex, and is the electron donor to plastocyanin. The 285-residue cytochrome f subunit is anchored in the thylakoid membrane of the chloroplast by a single membrane-spanning segment near the carboxyl terminus. A soluble redox-active 252-residue lumen-side polypeptide with native spectroscopic and redox properties, missing the membrane anchor and carboxyl terminus, was purified from turnip chloroplasts for structural studies. RESULTS: The crystal structure of cytochrome f, determined to 2.3 A resolution, has several unexpected features. The 252-residue polypeptide is organized into one large and one small domain. The larger heme-binding domain is strikingly different from known structures of other c-type cytochromes and has the same fold as the type III domain of the animal protein, fibronectin. Cytochrome f binds heme with an unprecedented axial heme iron ligand: the amino terminus of the polypeptide. CONCLUSION: The first atomic structure of a subunit of either the cytochrome b6f complex or of the related cytochrome bc1 complex has been obtained. The structure of cytochrome f allows prediction of the approximate docking site of plastocyanin and should allow systematic studies of the mechanism of intra- and inter-protein electron transfer between the cytochrome heme and plastocyanin copper, which are approximately isopotential. The unprecedented axial heme iron ligand also provides information on the sequence of events (i.e. cleavage of signal peptide and ligation of heme) associated with translocation of the cytochrome across the membrane and its subsequent folding.

Amino Acid Sequence↗
PubMed1994

Prospective fate map of the mouse primitive streak at 7.5 days of gestation.

Fluorescent dyes were used in the present study to map three rostrocaudal levels of the primitive streak of mouse embryos at 7.5 days of gestation. Injections at the most rostral level, the 1/4 streak level, principally labeled cells of the paraxial mesoderm, including mesenchyme in the head, and somites and segmental plate mesoderm in the trunk. Injections at the intermediate level, the 1/2 streak level, principally labeled cells of the lateral plate mesoderm of the trunk. Injections at the most caudal level, the 3/4 streak level, principally labeled cells of the extraembryonic mesoderm at the periphery (i.e., caudolateral portion) of the embryo adjacent to the developing amnion, yolk sac, and allantois. However, injections placed at all three primitive-streak levels provided some labeled cells to the areas of the ingressed mesoderm derived from immediately adjacent levels, suggesting that prospective mesodermal areas are not fully spatially segregated from one another at this stage. These data combined with those from a companion study in which the structure of the node was defined and its derivatives were mapped (Sulik et al. [1994] Dev. Dyn. 201:260-278) allowed us to construct a prospective fate map of the mouse primitive streak at 7.5 days of gestation. This map revealed that mediolateral subdivisions of the ingressed mesoderm were arrayed in rostrocaudal sequence within the primitive streak, such that more rostral levels of the streak contained prospective medial cells (e.g., notochord and paraxial mesoderm), intermediate levels contained prospective intermediate cells (e.g., intermediate mesoderm or nephrotome and lateral plate mesoderm), and more caudal levels contained prospective lateromost cells (e.g., extraembryonic mesoderm). Prospective mesodermal cells, with the exception of those of the notochord, ingressed bilaterally from the primitive streak, contributing to the mesoderm on both the right and left sides of the axis. Our prospective fate map of the mouse primitive streak at 7.5 days of gestation, when compared to a map of the avian primitive streak at a comparable stage of development (Schoenwolf et al. [1992] Dev. Dyn. 193:235-248), demonstrates that considerable congruity exists between the locations of mesoderm precursor cells in birds and mammals. Thus, similar morphogenetic movements underlie mesoderm formation during avian and mammalian gastrulation. Moreover, prospective mesodermal locations within the mouse primitive streak correspond to recently described patterns of early gene expression (Sasaki and Hogan [1993] Development 118:47-59; Takada et al. [1994] Genes Dev. 8:174-189; Rossant, person communication).

Animals↗
PubMed1994

Clinical relevance of intraoperative embolization detected by transcranial Doppler ultrasonography during carotid endarterectomy: a prospective study of 100 patients.

A study was performed to investigate the clinical significance of microembolization detected by transcranial Doppler ultrasonography (TCD) by determining the quantity and character of emboli and correlating these with neurological and psychometric outcome, fundoscopy, automated visual field testing and computed tomographic brain scans in 100 consecutive patients undergoing carotid endarterectomy. Embolization was detected in 92 per cent of successfully monitored operations. Most emboli were characteristic of air and not associated with adverse clinical outcome. However, more than ten particulate emboli during initial carotid dissection correlated with a significant deterioration in postoperative cognitive function. A relationship between persistent particulate embolization in the immediate postoperative period, and both incipient carotid artery thrombosis and the development of major neurological deficits was observed. Immediate intervention, based on TCD evidence of embolization, has the potential to avert neurological deficits resulting from particulate embolization.

Aged↗
PubMed1994

Detection of T-cell receptor beta chain mRNA in frozen and paraffin-embedded biopsy tissue using digoxigenin-labelled oligonucleotide probes in situ.

In situ hybridization techniques using a cocktail of digoxigenin-labelled T-cell receptor (TcR) constant (C) region beta oligonucleotide probes were used to detect TcR beta mRNA in frozen and paraffin-embedded tissue sections. The specificity of the C beta cocktail was confirmed by Northern blot analysis. The TcR C beta cocktail successfully hybridized to T cells in frozen and paraffin-embedded tissue obtained from patients with inflammatory arthropathies, B- and T-cell non-Hodgkin's lymphoma (NHL), and reactive tonsillitis, and showed staining patterns comparable to those obtained by conventional immunohistological detection of T cells. This is the first report of in situ studies using labelled TcR C beta oligonucleotide probes and may indicate the feasibility of investigating clonal T-cell populations using digoxigenin-labelled clonospecific probes in clinical samples in situ.

Biopsy↗