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Biomedical subjects

M E Adams

Publications and source records attributed to M E Adams.

At least 127 records · Page 7Linked to original sources
PubMed1989

Two classes of channel-specific toxins from funnel web spider venom.

1. The paralytic effects and neuromuscular actions of Agelenopsis aperta venom on insects were analyzed biochemically and electrophysiologically. 2. Paralysis caused by Agelenopsis venom is correlated with two effects on neuromuscular transmission: postsynaptic inhibition and presynaptic excitation. These effects are explained by the actions of two classes of toxins purified by RPLC, the alpha- and mu-agatoxins. 3. The alpha-agatoxins are low molecular weight, acylpolyamines which cause rapid, reversible paralysis correlated with use-dependent postsynaptic block of EPSPs and ionophoretic glutamate potentials. The mu-agatoxins are cysteine-rich polypeptides which cause irreversible paralysis and repetitive action potentials originating in presynaptic axons or nerve terminals. 4. The joint actions of the alpha- and mu-agatoxins lead to significantly higher rates of paralysis than are obtained by either toxin class alone, and this may relate to enhancement by excitatory mu-agatoxins of use-dependent block caused by alpha-agatoxins.

Action Potentials↗
PubMed1989

The effect of maturation and anterior cruciate ligament transection on the level of keratan sulfate in the serum of dogs.

The reactivity of 2 monoclonal antibodies, D1B2 and 7D1, to keratan sulfate is described. The reaction of both monoclonal antibodies to intact A1D1 proteoglycans was inhibited by isolated keratan sulfate chains. However, 7D1 was less reactive with the keratan sulfate chains bound to ELISA plates than it was to intact proteoglycan. The amount of keratan sulfate was determined in sera of 27 dogs (8 nonoperated, 6 sham operated and 13 ligament transected) between the ages of 305 and 691 days using these monoclonal antibodies in an inhibition ELISA. The level of keratan sulfate as measured by D1B2 but not that by 7D1 decreased significantly with age. The concentration of keratan sulfate was relatively constant between the ages of 450 and 691 days. When controlled for age, no apparent difference could be shown in the level of keratan sulfate in the serum of the dogs as a result of the procedure (ligament transection or sham operation) or time after operation.

Aging↗
PubMed1989

Cartilage hypertrophy following canine anterior cruciate ligament transection differs among different areas of the joint.

Transection of the canine anterior cruciate ligament is used widely as a model of osteoarthritis (OA). The results from studies using this model have sometimes differed, but various areas of the joint have been compared. In other studies, the exaggerated chondrocyte synthetic response in the medial femoral condyle in this model which leads to hypertrophic repair was characterized. In this study the magnitude of this reaction was analyzed in 8 anatomically defined areas of the joint using 28 dogs followed from 3 days to 64 weeks after transection of the anterior cruciate ligament, 8 nonoperated control animals and 7 sham operated control animals. The results show that the in vivo reaction differs markedly among different anatomical areas of the joint. This suggests that the response is modulated by differences in the biomechanics of the joint. Furthermore, it suggests caution in comparing results of studies of OA cartilage if different areas of the joint have been used.

Animals↗
PubMed1988

Properties of purified actin depolymerizing factor from chick brain.

Actin depolymerizing factor (ADF) from 19-day embryonic chick brains has been purified to greater than 98% homogeneity with a yield of 7.2 mg/100 g of brain. Quantitative immunoblotting with a monospecific antibody to ADF indicated that ADF comprises 0.3% of the total brain protein, resulting in an actual purification yield of about 20%. Brain ADF migrates as a single polypeptide of 19,000 kDa on SDS-containing polyacrylamide gels. The molecular weight of the native protein determined from sedimentation equilibrium in buffers containing from 50 to 200 mM KCl is 20,000. The secondary structure of ADF calculated from the circular dichroic spectrum consists of about 22% alpha-helix, 24% beta-sheet, and 18% beta-turn. ADF contains a blocked N-terminus, a single tryptophan residue located about one-third of the way from one end of the protein, and six cysteine residues (all in reduced form in the native protein). All six cysteine residues could be chemically modified with eosinylmaleimide under nondenaturing conditions; however, ADF activity was lost when more than one cysteine residue was modified. ADF microheterogeneity has been observed upon nonequilibrium pH gradient electrophoresis in polyacrylamide gels containing 9 M urea, the major isoform having a pI of congruent to 7.9-8.0. ADF can interact with either monomeric or filamentous actin to give a complex which can be isolated by gel filtration chromatography. Both major and minor isoforms of the ADF are found in the complex. Assembly-competent actin and active ADF can both be recovered from the complex by chromatography on ATP-saturated DEAE-cellulose.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Depolymerizing Factors↗
PubMed1988

Effect of fatiguing resistive loads on the level and pattern of respiratory activity in awake goats.

The effect of respiratory muscle fatigue on inspiratory muscle electrical activity (EMG), transdiaphragmatic pressure and ventilation during spontaneous breathing was examined in three awake goats. Studies were performed during progressive hypercapnia before and immediately after inspiratory muscle fatigue induced by flow resistive loading (IRL). IRL caused a decrease in the high-low ratio of the diaphragm and intercostal EMG and a decrease in Pdi during electrophrenic stimulation. After IRL, inspiratory time, the breathing duty cycle (inspiratory time/total breath cycle time), peak integrated activity of the diaphragm and external intercostal EMG per breath and per minute were all decreased at any given level of PCO2. Changes in the timing of respiratory motor activity and reduced muscle performance after IRL resulted in a decrease in transdiaphragmatic pressure and ventilation during hypercapnia. In conscious goats studied during spontaneous, chemically stimulated breathing, inspiratory muscle fatigue is associated with reductions in diaphragm and external intercostal muscle electrical activity and reductions in transdiaphragmatic pressure and ventilation.

Animals↗
PubMed1988

Interactions between entorhinal axons and target hippocampal neurons: a role for glutamate in the development of hippocampal circuitry.

A coculture system consisting of input axons from entorhinal cortex explants and target hippocampal pyramidal neurons was used to demonstrate that glutamate, released spontaneously from afferent axons, can influence both dendritic geometry of target neurons and formation of presumptive synaptic sites. Dendritic outgrowth was reduced in hippocampal neurons growing on entorhinal axons when compared with neurons growing off the axons. Presumptive presynaptic sites were observed in association with hippocampal neuron dendrites and somas. HPLC analysis showed that glutamate was released from the explants in an activity- and Ca2(+)-dependent manner. The general glutamate receptor antagonist D-glutamylglycine significantly increased dendritic outgrowth in pyramidal neurons associated with entorhinal axons and reduced presumptive presynaptic sites. Tetrodotoxin and reduction of extracellular Ca2+ also promoted dendritic outgrowth and reduced the formation of presumptive synaptic sites. The results suggest that the neurotransmitter glutamate may play important roles in the development of hippocampal circuitry.

Animals↗
PubMed1988

Ultrastructural changes in the femoral condylar cartilage of mature American foxhounds following transection of the anterior cruciate ligament.

Skeletally mature male American foxhounds were subjected to surgical transection of the right anterior cruciate ligament; they developed osteoarthritis of this stifle joint. The results were compared with joints from sham operated and nonoperated controls. Articular cartilage from each lateral femoral condyle was viewed by transmission electron microscopy. The ultrastructure of control and of experimental tissues was compared with that of similar, previous studies made in beagles. Both forms of foxhound control tissue were indistinguishable from normal beagle femoral condylar cartilage. Ultrastructural changes observed in the foxhound up to 16 weeks after cruciate ligament surgery were closely similar to those recorded in the beagle; they included alterations of chondrocyte morphology and the deposition of an electron dense cartilage surface coat. However, the degree of cartilage disorganization after 64 weeks was greater than, and qualitatively distinct from, that observed in the beagle.

Animals↗
PubMed1987

Structures and biological activities of three synaptic antagonists from orb weaver spider venom.

The venom of Argiope aurantia, an orb weaver spider, contains a mixture of low molecular weight "argiotoxins", which block neuromuscular transmission in insects. Complete structure elucidation of three argiotoxins reveals common features; a hydrophilic, basic domain of arginine, a polyamine and asparagine is connected to an aromatic moiety contributed either by 4-hydroxyindole-3-acetic acid or 2,4-dihydroxyphenylacetic acid. Structural assignments of two argiotoxins are verified by chemical synthesis. The argiotoxins cause reversible paralysis when injected into insects and this is correlated with a stimulus-dependent inhibition of skeletal neuromuscular transmission at submicromolar concentrations.

Animals↗
PubMed1987

Magnetic resonance imaging of osteoarthritis: correlation with gross pathology using an experimental model.

Conventional radiography has several limitations in the study of osteoarthritis (OA): changes occur late, they are restricted to bone, and they do not correlate well with the patient's symptoms. Magnetic resonance imaging (MRI) can visualize with great detail the soft tissue changes in and around joints. We have obtained MR images of knees using an experimental model of OA in order to study the early changes of OA, to correlate the images with the gross pathology, and to compare MR images with radiographs. The changes on MRI correlated with the gross pathological changes as assessed by Kendall's rank correlation test as follows: meniscal changes, tau = 0.58 (p less than 0.01); osteophytes, tau = 0.59 (p less than 0.05); capsular fibrosis, tau = 0.55 (p less than 0.05); and overall, tau = 0.68 (p less than 0.001). Abnormalities were evident on MRI as early as 4 weeks after the onset of the disease, which is 8 weeks before they appear on radiographs. Thus, MRI can show changes in OA earlier than radiography can, and the images correlate with the gross pathology.

Animals↗
PubMed1987

Degeneration and the chemical composition of the human lumbar intervertebral disc.

Fifteen lumbar spines were collected postmortem. The intervertebral discs were assigned morphological grades and were analyzed for water, collagen, and proteoglycan. In order of increasing degeneration, five grade 0, four grade 1, 45 grade 2, 12 grade 3A, and nine grade 3B discs were identified. The proteoglycan concentration fell progressively with increasing grade, although the concentrations of each component overlapped extensively among the grades. Grade 2 discs showed no consistent differences from adjacent grade 3A or 3B discs in the same spine. All discs in seven of the eight spines with grade 3A or 3B discs and all discs in three spines with no grade 3A or 3B discs had proteoglycan concentrations below 52 mg/g fresh weight. Four of five spines with at least one disc of proteoglycan concentration above this value contained no grade 3A or 3B discs. These observations support the hypothesis that low proteoglycan concentrations in all the discs of a spine precede degeneration.

Adult↗
PubMed1987

Localization of glycosaminoglycans in human and canine menisci and their attachments.

The semilunar meniscal body, horns and peripheral attachment were dissected from human and canine knee joints. The concentrations of hyaluronate, chondroitin sulfate, dermatan sulfate and keratan sulfate differed markedly among the tissues. The meniscal body was fibrocartilaginous but showed marked histological microheterogeneity with hyalinized areas intermixed with fibrous areas and contained mostly chondroitin sulfate and keratan sulfate. On the other hand, the fibrous peripheral attachment contained mostly dermatan sulfate and hyaluronate and almost no keratan sulfate and the ligamentous horns contained mostly dermatan sulfate and chondroitin sulfate. Human menisci contained more dermatan sulfate and less chondroitin sulfate than did canine menisci. From morphometric measurements of canine menisci, an estimate was made of the amount of peripheral tissue which had been included with the body when dissections were based on gross appearance and how much this might influence analysis of the composition. This local variation emphasises the need for careful anatomical description in studies of the composition of menisci, but suggests that previously noted changes in the composition of menisci in osteoarthritis result from the disease, not dissection differences.

Aged↗
PubMed1987

Cartilage proteoglycan changes in experimental canine osteoarthritis.

Articular cartilage contains at least 2 proteoglycans (PGs) which aggregate with hyaluronate: one larger, richer in chondroitin sulphate (CSRPG); the other smaller, relatively richer in keratan sulphate (KSRPG). With maturation the ratio of CSRPG/KSRPG decreases. In order to test the hypothesis that osteoarthritic cartilage contains an increased amount of proteoglycans characteristic of immature cartilage, experimental osteoarthritis (OA) was induced in 11 dogs by transection of the anterior cruciate ligament. Proteoglycan populations were assessed by composite agarose polyacrylamide gel electrophoresis (CAPAGE). The OA cartilage had more proteoglycan and an increased proportion of the slower migrating band on CAPAGE, which corresponds to the CSRPG, supporting the hypothesis that OA cartilage contains an increased amount of proteoglycans characteristic of immature cartilage.

Animals↗
PubMed1986

Peptidergic innervation of insect reproductive tissue: the association of proctolin with oviduct visceral musculature.

The visceral muscles of the oviducts of Locusta migratoria are sensitive to the pentapeptide proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH). Amounts of proctolin as low as 2 fmol induce a tonic contraction that is dose-dependent up to 200 fmol. By use of this bioassay we have quantified the amount of material showing proctolinlike bioactivity associated with the oviducts. Reversed-phase high performance liquid chromatography of tissue extracts indicates that material with proctolinlike bioactivity and co-eluting with proctolin is present in the oviducts, the oviducal nerve, and the VIIth abdominal (penultimate) ganglion. The proctolin is present in areas of oviduct that receive extensive innervation. There is tenfold less proctolin in areas of oviduct that receive little or no innervation. Proctolinlike immunoreactivity is present in axons of the oviducal nerve as well as in a number of cell bodies in the VIIth abdominal ganglion. Three of these neurons lie in a position similar to that of the previously described oviduct motoneurons. Neuropilar axons and processes, as well as axons in the median nerve, also show proctolinlike immunoreactivity. The results indicate that proctolin, which has previously been identified as a neurotransmitter of insect hindgut visceral muscle, is also associated with visceral muscle of the reproductive system.

Animals↗
PubMed1986

Magnetic resonance imaging of the ligaments and menisci of the knee.

Although the technique is still developing and the data are preliminary, MRI will likely be the best noninvasive method for evaluating the ligaments and menisci of the knee. It can provide valuable and accurate information, especially in the acutely injured knee. The presence, extent, and exact location of cruciate ligament disruption can be visualized. This is useful in patients in whom the clinical diagnosis is uncertain and provides valuable information in preoperative planning. Equally important is the ability of MRI to provide diagnostic information about associated injuries to the collateral ligaments, capsule, menisci, articular cartilage, and subchondral bone. Proper pulse sequence selection is important. T2-weighted spin-echo sequences are best for visualizing injuries to the ligaments and menisci, and T1-weighted sequences (inversion-recovery or spin-echo with a short TR and a short TE) are more helpful in evaluating cartilaginous and bony abnormalities.

Arthroscopy↗
PubMed1986

Isolation and characterization of high-buoyant-density proteoglycans from semilunar menisci.

Proteoglycans were extracted from adult canine menisci in high yield and were purified, and the major species were characterized biochemically. Most proteoglycans in menisci were isolated in the high-buoyant-density fraction. By agarose-acrylamide composite gel electrophoresis, two proteoglycans were seen in this fraction. Although they were smaller than those from porcine laryngeal hyaline cartilage and had shorter chondroitin sulphate and keratan sulphate chains and a lower carbohydrate-to-protein ratio, they were functionally similar to those in hyaline cartilage in their specific interaction with hyaluronate.

Animals↗
PubMed1985

Automation of 1,9-dimethylmethylene blue dye-binding assay for sulfated glycosaminoglycans with application to cartilage microcultures.

The 1,9-dimethylmethylene blue dye-binding assay for sulfated glycosaminoglycans has been modified and adapted for use on a Technicon autoanalyzer. The assay was linear for chondroitin sulfate from 2.5 to 500 micrograms/ml and used only 2.5 microliters sample. Interference by salts and solvents commonly used in proteoglycan research was minimal and could be compensated for by using standards in the appropriate solvent. High concentrations of albumin and serum interfered strongly but most of the inhibition could be overcome by papain digestion.

Animals↗
PubMed1985

Model peptidergic systems at the insect neuromuscular junction.

The emergence of neuropeptides as a prominent neurotransmitter class raises fundamental new questions about modes of chemical signaling in the nervous system. These relate to the large number of peptides, their co-localization in neurons and to novel actions at innervated targets. Synaptic preparations in insects offer excellent experimental models for studies of multiple transmitters and their joint actions at uniquely identified nerve-muscle junctions. Peptidergic systems in insects are reviewed with particular reference to two identified neuromuscular preparations which demonstrate cotransmitter actions of peptides and "classical" neurotransmitter substances.

Animals↗