Search PubMed⌕ Search

Biomedical subjects

M M Smith

Publications and source records attributed to M M Smith.

At least 181 records · Page 10Linked to original sources
PubMed1986

The effects of inhibiting oligosaccharide trimming by 1-deoxynojirimycin on the nicotinic acetylcholine receptor.

The nicotinic acetylcholine receptor has a subunit stoichiometry of alpha 2 beta gamma delta; all 5 subunits contain N-linked oligosaccharides. We investigated what role trimming of the oligosaccharides played in the post-translational processing of the subunits and assembly of the receptor by examining the receptor synthesized in the presence of an inhibitor of oligosaccharide trimming, 1-deoxynojirimycin. BC3H-1 cells express one-third fewer receptors when grown in the presence of 1-deoxynojirimycin. The receptor subunits that are expressed have decreased mobility by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating an inhibition of oligosaccharide trimming. In control cells, 40% of the translated alpha subunit acquires the capacity to bind alpha-bungarotoxin with a half-time of 40 min before assembly with the other subunits; the rest is rapidly degraded. In 1-deoxynojirimycin-treated cells approximately the same amount of alpha subunit is translated as in control cells, but that alpha subunit is degraded more rapidly, and only 25% acquires the capacity to bind alpha-bungarotoxin. From these results, we conclude that oligosaccharide processing either may aid in protecting the alpha subunit primary translation product from degradation or may be required for the conformational change or other post-translational modification(s) necessary for formation of the alpha-bungarotoxin binding form of the alpha subunit, which is then protected from proteolytic degradation. The cell surface receptor that is expressed in the presence of 1-deoxynojirimycin, however, is not altered in its affinity for cholinergic ligands. Thus, we conclude that differential N-linked oligosaccharide trimming of the 2 alpha subunits does not appear to play a part in the differences in affinities of the 2 alpha subunits for cholinergic ligands.

1-Deoxynojirimycin↗
PubMed1986

Evaluation of a modified castellated laryngofissure for alleviation of upper airway obstruction in dogs with laryngeal paralysis.

A modified castellated laryngofissure procedure (castellated laryngofissure, vocal fold resection, and bilateral arytenoid lateralization) was performed on 12 dogs with bilateral laryngeal paralysis. Clinical signs of airway obstruction were assessed and a pulmonary function test (tidal breathing flow volume loop) was used to evaluate the severity of obstruction. The dogs were evaluated before surgery and at various periods from 4 days to 15 months after surgery. One dog died immediately after surgery and 3 dogs died due to nonrelated or unknown causes 1, 9, and 11 months after surgery. Clinical signs of upper airway obstruction disappeared or decreased in severity in the 11 dogs that recovered from surgery. Tidal breathing flow volume loop values were normal in 7 of 10 dogs evaluated within 5 to 189 days after surgery. The modified castellated laryngofissure procedure provided successful long-term relief of upper airway obstruction associated with bilateral laryngeal paralysis.

Airway Obstruction↗
PubMed1986

Increased ketogenesis in hyperthyroid rats metabolizing ethanol.

The levels of various metabolites were measured in freeze-clamped samples of liver from triiodothyronine-treated and control rats to which either saline or ethanol (2.5 g/kg body weight) had been administered 2 hours earlier. It was found that ethanol led to a sharp increase in the hepatic acetate concentration in both hyperthyroid and euthyroid rats whereas lactate and pyruvate concentrations were lowered in both groups. The lactate/pyruvate ratio rose significantly in euthyroid animals that had received ethanol but the ratio remained relatively low in hyperthyroid rats. The adenine nucleotide phosphorylation potential, already low in hyperthyroid rats, was further lowered by ethanol. However, the most remarkable difference between the responses of euthyroid and hyperthyroid rats to ethanol was in the hepatic concentrations of ketone bodies, particularly 3-hydroxybutyrate. In control animals, administration of ethanol did not affect either the acetoacetate or 3-hydroxybutyrate concentration but, although the level of ketone bodies in the livers of hyperthyroid rats that had not received ethanol was the same as that of controls, there was a greater than fivefold increase in the 3-hydroxybutyrate level when ethanol was given. While this increase in ethanol-dependent ketogenesis is not explicable at this stage, hyperthyroidism did not increase the activity of cytoplasmic acetyl-CoA synthetase, an enzyme that is probably involved in the formation of ketone bodies from ethanol-derived acetate.

3-Hydroxybutyric Acid↗
PubMed1986

Apparent translocation of glucose transport activity in rat epididymal adipocytes by insulin-like effects of high pH or hyperosmolarity.

The basal and plus insulin states of glucose transport activity in adipocytes are known to show different responses to changes in the pH or osmolarity of the incubation mixture. When the pH was raised from 7 to 8, the basal glucose transport activity (assessed from the rate of 3-O-methyl-D-glucose uptake) was increased approximately 3-fold while the plus insulin activity remained virtually unaffected. Likewise, when cells were exposed to 300 mM sorbitol, the basal glucose transport activity, but not the plus insulin activity, was considerably increased. In both cases, the change in the transport activity was ATP-dependent and was completed in approximately 60 min. The increase in the cellular glucose transport activity was accompanied, in both cases, by an increase in the glucose transport activity in the plasma membrane fraction and a decrease in the activity in the high-speed pellet fraction. The transport activity in the subcellular fractions was determined after reconstitution into egg lecithin liposomes. Both isotonic buffer at pH 8.0 and hypertonic buffer at pH 7.4 significantly stimulated membrane-bound cAMP phosphodiesterase in adipocytes. It is concluded that the above two experimental conditions may induce insulin-like effects in fat cells and may facilitate translocation of the glucose transport activity from an intracellular site to the plasma membrane.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

The effects of some polysulphated polysaccharides on hyaluronate (HA) synthesis by human synovial fibroblasts.

The in vitro synthesis of HA in synovial fibroblasts derived from normal and rheumatoid joints was investigated. Incubation of these cells with ArteparonR and a variety of sulphated dextrans showed that macromolecular HA synthesis could be modified by these drugs. ArteparonR and a dextran sulphate (DS1) of molecular weight 20,600 and 0.8 sulphate substitution stimulated HA synthesis in rheumatoid cells by approximately 150%. In contrast the dextrans with higher sulphate substitution but similar molecular weight were less effective. Gel filtration chromatography of media from drug-treated cells showed an increase in HA hydrodynamic size.

Arthritis, Rheumatoid↗
PubMed1986

Fine-structure analysis of the DNA sequence requirements for autonomous replication of Saccharomyces cerevisiae plasmids.

An autonomously replicating segment, ARS, is located 293 base pairs downstream from the histone H4 gene at the copy-I H3-H4 locus. The sequences needed for autonomous replication were defined by deletion analysis to include an ARS consensus sequence and an additional 3'-flanking region. External deletions into the 3'-flanking yeast sequences resulted in a loss of replication function. However, disruptions of the required 3'-flanking domain by either 10-base-pair linker-scanning substitutions or larger internal deletions did not impair autonomous replication. Thus, replication is dependent upon a flanking chromosome domain, but not an exact DNA sequence. The extent of the yeast sequences required in the 3'-flanking domain is variable depending on the nature of neighboring plasmid vector sequences. That is, there are certain vector sequences that prohibit replication when they are placed too close to the ARS consensus. These results suggest that the functional 3'-flanking domain of the H4 ARS is a specific DNA or chromatin structure or both.

Base Sequence↗
PubMed1986

Treatment of endometriosis in monkeys: effectiveness of continuous infusion of a gonadotropin-releasing hormone agonist compared to treatment with a progestational steroid.

The use of a GnRH agonist or a progestational steroid (levonorgestrel) for the treatment of endometriosis in monkeys was compared. Four monkeys with spontaneous endometriosis were treated for 6 months with a continuous infusion of a GnRH agonist (25 micrograms/day). Five animals with surgically induced endometriosis were treated with the same agonist for 3 months. An additional group of five monkeys with surgically induced endometriosis was treated orally with levonorgestrel (1 mg/kg X day), while a final group of four monkeys served as untreated controls. During agonist treatment, the four monkeys with spontaneous endometriosis gained body weight and had a greater than 80% decline in cyst size (representing a decline in secretory activity). Monkeys with surgically induced endometriosis had almost total resolution of endometrial lesions during agonist treatment, which was maintained throughout a 4-month posttreatment period. After initial stimulation at the onset of the GnRH agonist infusion, serum LH, FSH, estradiol, and progesterone levels decreased to near the levels of detection, where they remained until treatment was terminated. In comparison, levonorgestrel reduced endometrial lesion size, but the monkeys did not resume normal cycles as early as those treated with the agonist. Levonorgestrel-treated monkeys had normal serum LH and FSH levels, but low serum estradiol and progesterone levels. The results of this study indicate that either continuous infusion of a GnRH agonist or administration of levonorgestrel is effective for treating endometriosis in monkeys. The hormonal data suggest that the GnRH agonist acts at the level of the hypothalamus and pituitary, whereas levonorgestrel acts at the ovarian level.

Animals↗
PubMed1986

The simplified HF E-800 high-frequency audiometer: clinical applications.

In a prior study (Gauz and Smith, J. Aud. Res., 1985, 25, 101-122) threshold tracings were collected at 8-20 kc/s on 108 Ss using a Bekesy-type Simplified High-Frequency Audiometer (SHF E-800) set in the fixed-frequency mode. Of these, 23 Ss did not meet screening criteria for a normative study; their data are reported here. Examples are given of HF audiometric results on Ss with one or more conditions affecting hearing thresholds, including age, conductive pathologies, noise exposure, cardiovascular disorders, hearing loss in the conventional audiometric frequencies, and a miscellaneous category. Results were obtained generally in line with expectations based on literature review. The present case studies provide information useful in the clinical application of HF audiometry.

Adult↗
PubMed1986

Upper airway obstruction in canine laryngeal paralysis.

The type and the severity of airway obstruction in 30 dogs with bilateral laryngeal paralysis was assessed, using tidal breathing flow-volume loop (TBFVL) analysis. The dogs had clinical evidence of mild-to-severe upper airway obstruction (ie, respiratory distress, exercise intolerance, stridor). Seventeen dogs had TBFVL consistent with a nonfixed (inspiratory) obstruction, 10 had TBFVL indicative of a fixed (inspiratory/expiratory) obstruction, and 3 had normal TBFVL. Analysis of TBFVL confirmed that dogs with laryngeal paralysis have upper airway obstruction that differs in type and severity. Use of TBFVL provided a quantitative evaluation of airway obstruction and demonstrated the effects of bilateral laryngeal paralysis on the breathing patterns of dogs.

Airway Obstruction↗
PubMed1985

Effect of triiodothyronine on alcohol dehydrogenase and aldehyde dehydrogenase activities in rat liver. Implications for the control of ethanol metabolism.

Treatment of rats with 20 micrograms of 3,3',5-triiodo-L-thyronine (T3) per 100 g body wt for a period of 6 days led to a 45% decrease in total liver alcohol dehydrogenase and a 36% decrease in total liver aldehyde dehydrogenase. Most of the latter decrease was directly attributable to a 57% fall in the level of the physiologically-important low Km mitochondrial isoenzyme. The high Km isoenzyme of the postmitochondrial and soluble fractions was much less affected by T3-treatment. T3, at concentrations up to 0.1 mM, did not inhibit the activity of aldehyde dehydrogenase in vitro. Despite these large losses of the two enzymes most intimately involved in ethanol metabolism, the rate of ethanol elimination in vivo was the same in T3-treated and control animals. Moreover, there was no difference between the two groups in the susceptibility of ethanol elimination to inhibition by 4-methylpyrazole, making it unlikely that an alternative route of ethanol metabolism had been significantly induced by treatment with T3. As it had been suggested that T3 might create a "hypermetabolic state" in which constraints normally imposed on alcohol dehydrogenase and aldehyde dehydrogenase are removed thereby compensating for any loss in total enzymic activity, 2,4-dinitrophenol (0.1 mmoles/kg body wt) was administered to rats in order to raise the general metabolic rate. However, the uncoupler proved to be lethal to T3-treated animals and did not stimulate ethanol elimination in controls. The results do not support the notion that ethanol elimination in vivo is normally governed either by the level of alcohol dehydrogenase or by that of hepatic aldehyde dehydrogenase. However, the mode of control remains unclear.

Alcohol Dehydrogenase↗
PubMed1985

Clinical evaluation of dogs after surgical and nonsurgical management of osteochondritis dissecans of the talus.

Osteochondritis dissecans of the medial aspect of the talus was diagnosed in 17 joints in 11 dogs. In 10 of the 11 dogs, intermittent lameness had persisted after initial diagnosis and therapy. Radiographs made during the initial examination showed a widening of the medial tarsocrural joint space, with osteophyte formation involving the medial and caudal tarsocrural joint. The follow-up radiographs showed greatest change in the increase in reactive bone formation, especially involving the medial and caudal aspects of the tarsocrural joint and the medial aspect of the talus. Arthrotomy for flap removal and curettage was performed on 11 joints; 6 joints did not receive surgery. After a mean period of 34 months following diagnosis, the dogs were examined clinically and the affected joints were radiographed. The degree of lameness, range of motion, and stability of the tarsocrural joint were graded for each limb. Radiographic determinants that were assessed included: width of the medial tarsocrural joint space, medial tarsocrural osteophyte formation, lateral tarsocrural osteophyte formation, caudal tarsocrural osteophyte formation, medial talus osteophyte formation, lateral talus osteophyte formation, intertarsal osteophyte formation, subchondral sclerosis of the distal end of the tibia, presence of joint bodies, and periarticular soft-tissue thickness. On the basis of clinical and radiographic evaluations, the surgical procedures described in this report did not modify progression of osteoarthritic changes.

Animals↗
PubMed1985

A correlative study of the clinical and radiographic signs of periodontal disease in dogs.

Twenty-four dogs admitted for routine teeth cleaning were selected arbitrarily to undergo a periodontal examination and a dental radiographic examination before the dental procedure. Data pertaining to the physical and radiographic manifestations of periodontal disease of 783 teeth were collected. All dogs had lesions consistent with periodontal disease, ranging from mild gingivitis and minimal plaque accumulation to severely inflamed gingiva, exuberant calculus formation, and root exposure. Of the 783 teeth examined, 153 (20%) had a pocket depth greater than or equal to 4 mm and less than or equal to 9 mm. Data regarding these teeth were subjected to statistical analysis. The clinical signs of plaque, calculus, mobility, pocket depth, and furcation were positively associated with radiographic signs of periodonta disease. The association between grossly evident gingivitis and radiographic signs of periodontal disease was not significant. Conditional probability analysis was applied to determine confidence intervals for the probability of a radiographic sign of periodontal disease occurring given that a clinical sign of periodontal disease occurs.

Animals↗
PubMed1985

Effects of monensin on insulin processing in adipocytes. Evidence that the internalized insulin-receptor complex has some physiological activities.

In the presence of 10-100 microM monensin (a monovalent cation ionophore), a considerable amount of 125I activity of iodoinsulin accumulated in isolated rat epididymal adipocytes during a 30-min incubation. The accumulation was secondary to the action of monensin to inhibit dissociation of a certain fraction of the cellbound 125I activity. This monensin effect was reversible. The accumulation of 125I activity was ATP dependent and so was the discharge of the accumulated radioactivity. Approximately 91% of the accumulated radio-activity was precipitable with trichloroacetic acid, and at least 84% was reactive to anti-insulin antibody. Monensin at 100 microM appeared to have only mild effects on the cellular activities of glucose transport and cAMP phosphodiesterase. Nevertheless, when cells were first exposed to 10 nM insulin in the presence of 100 microM monensin and then transferred into a hormone-free buffer that contained monensin, the phosphodiesterase activity in cells remained partially activated as if cells were kept exposed to approximately 0.5 nM insulin. Under similar conditions, glucose transport activity remained partially activated as if cells were incubated with approximately 70 pM insulin. Monensin did not inhibit the reversal of the insulin effect per se. Like monensin, 20-100 microM chloroquine (a lysosomotropic inhibitor) induced a considerable accumulation of [125I] iodoinsulin. However, cells that had been exposed to insulin in the presence of chloroquine retained little hormonal effect after washing. Based on these observations and on the reported biological effects of monensin, it is suggested (a) that monensin may induce intracellular accumulation of the insulin-receptor complex by blocking the acidification of endocytic vesicles and (b) that the accumulated insulin-receptor complex may retain a weak, but significant, capacity to stimulate both glucose transport and phosphodiesterase activities.

Adenosine Triphosphate↗
PubMed1985

Use of an oligonucleotide probe to detect transplacement of an amber mutation into a yeast histone H3 gene.

We have used a synthetic 17-mer to direct mutagenesis of the cloned yeast histone H3 gene HHT2, creating an amber mutation at amino acid 41. This point mutation did not alter the restriction pattern of the HHT2 gene nor was it expected to provide an easily scorable phenotype in vivo. Therefore, nucleic acid hybridization was used to detect this point mutation during strain construction. The oligonucleotide was used to probe yeast genomic Southern blots to detect integration of the plasmid bearing the mutant HHT2 gene into the genome, and then to score the eventual excision of the plasmid vector with retention of the mutant gene on the chromosome. This technique can be used to score virtually any engineered point mutations in yeast.

Gene Conversion↗
PubMed1985

Effect of a gonadotropin-releasing hormone agonist on luteinizing hormone and testosterone secretion and testicular histology in male rhesus monkeys.

Three adult male rhesus monkeys were treated for 20 weeks with a gonadotropin-releasing hormone (GnRH) agonist (Ag; Wy-40972; Wyeth Laboratories, Philadelphia, PA) using osmotic minipumps. Ag administration resulted in a transient increase and then a precipitous decrease in the concentration of luteinizing hormone (LH) and testosterone (T). After 5 weeks, serum levels of LH were undetectable (less than 0.2 microgram/ml), while serum T was always detectable, but continued to fall throughout the period of Ag administration. The serum LH and T response to 50 micrograms of GnRH was abolished by 4 weeks of Ag treatment, and this effect persisted through the treatment period. Testicular histology at 20 weeks of Ag treatment exhibited diffuse atrophy of seminiferous tubules, suppressed germinal cell division, and the absence of spermatids or spermatozoa. There was no evidence of testicular necrosis or calcification of the seminiferous tubules. Following the termination of Ag infusion, serum LH and T concentrations rebounded to levels that exceeded pretreatment values for a 5-week period before falling back to baseline levels. A complete restoration of spermatogenesis and testicular volume occurred by 12 weeks after treatment. These data suggest that continuous Ag administration is an effective method of reversibly disrupting spermatogenesis in the male rhesus monkey.

Animals↗
PubMed1985

Behavioral cohabitation: increasing satisfaction among nonmarried dyads?

The present study reports upon a standard behavior therapy treatment package applied to three clinically referred cohabitating couples. Multidimensional assessment measures included reports by self, partner, and external observers of couples' interactions. Moreover, a multiple-baseline design across couples was employed as a means of evaluating treatment efficacy. Therapy involved the weekly administration of bibliotherapy and exercise material, with therapist contact purposely minimized. An analysis of results indicates modest treatment success with considerable between-subject variability. These findings are discussed with regard to gender differences, ceiling effects, and utilization of standardized therapy packages. Recommendations are made for future behavioral cohabitation research.

Adult↗
PubMed1985

Regulation of cyclic AMP metabolism by muscarinic cholinergic receptors.

The occurrence of muscarinic cholinergic receptor-mediated activation of phosphodiesterase in 1321N1 cells does not represent an isolated phenomenon, since a similar response to cholinergic stimuli is observed in thyroid slices (45) and WI-38 fibroblasts (1,42). Both muscarinic-receptor-mediated inhibition of adenylate cyclase and activation of phosphodiesterase occur in WI-38 fibroblasts (42). Work currently under way in our laboratory is directed toward determining if a guanine nucleotide regulatory protein is involved in the activation of phosphodiesterase in these cells and whether common or separate populations of muscarinic receptors are coupled to these two mechanisms of cyclic AMP metabolism. The analysis of acute hormonal regulation of phosphodiesterase in intact cells is sufficiently complicated to have previously discouraged investigators from pursuing this question in mammalian tissues. The 1321N1 cell line provides a simple model system in which at least one mechanism of hormonal regulation of phosphodiesterase can be examined. In light of the widespread occurrence of muscarinic-receptor-mediated effects on Ca2+ mobilization, it would not be surprising to find that this mechanism represents an important part of cholinergic action in both the peripheral and central nervous systems. Indeed, this system could provide an important regulatory link between Ca2+ -mediated and cyclic-AMP-mediated events in target cells. The potential importance of such a mechanism also need not be restricted to the muscarinic receptor system, since any neurotransmitter or hormone receptor system coupled to events involved in Ca2+ mobilization might produce phenomena similar to that observed for muscarinic receptors in 1321N1 cells. Our studies emphasize that two mechanisms for regulation of cyclic AMP accumulation by muscarinic cholinergic receptors exist. The data to date suggest that separate receptor subtypes are involved in these mechanisms of cholinergic regulation and provide another biochemical basis whereby the well-known interaction of Ca2+ with the cyclic AMP system can be effected. Thus, identification of the molecular events involved in the regulation of PI turnover and its consequences may be crucial in defining the basis of this aspect of cholinergic action. In addition, more extensive analyses of the phosphodiesterase system using cell-free preparations have the potential of providing clues to the molecular basis of this mechanism.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Diphosphate Ribose↗