Biomedical subjects

R J Martin

Publications and source records attributed to R J Martin.

At least 19 recordsLinked to original sources

PubMed1992

Detection of alveolar macrophage-derived IL-1 beta in asthma. Inhibition with corticosteroids.

This study investigated alveolar macrophage function in asthma as assessed by the presence and source of the cytokine IL-1 beta. Bronchoalveolar lavage (BAL) fluid and cell pellets were obtained at 4 a.m. from a cohort of asthmatic subjects. Normal subjects were used as controls. Asthmatic BAL fluid contained 57.0 +/- 5.9 pg/ml of IL-1 beta as determined by ELISA. No IL-1 beta could be identified in the BAL fluid of the control group. This IL-1 represented synthesis by cells of the airway as assessed by the presence of IL-1 beta-specific mRNA transcripts in the BAL cell pellets. Inasmuch as IL-1 beta transcripts are known to be present for only a short time period after activation (approximately 0.5 to 16 h), the presence of transcripts represents recent cellular activation. Using the technique of in situ hybridization, IL-1 beta transcripts were found to be located exclusively within alveolar macrophages, and a mean of 40 +/- 14% of alveolar macrophage were activated at the time of the lavage. Corticosteroids are known to be efficacious in the treatment of asthma. Administration of a single 50-mg dose of prednisone at 3 p.m. resulted in diminished IL-1 beta protein concentration in the BAL fluid (28.3 +/- 5.7 pg/ml; p < 0.01 compared to baseline) and completely abrogated IL-1 beta mRNA expression. In summary, these studies demonstrate that IL-1 beta is synthesized within the airways by alveolar macrophage and suggest that IL-1 beta may be a mediator of asthma. Inhibition of IL-1 beta may be an additional mechanism for the efficacy of corticosteroids in the treatment of asthma.

Asthma↗

PubMed1992

Distribution of a fluorescent ivermectin probe, bodipy ivermectin, in tissues of the nematode parasite Ascaris suum.

A fluorescent derivative of the anthelmintic ivermectin (4''-5,7-dimethyl bodipy proprionylivermectin, referred to hereafter as bodipy ivermectin) was synthesized for an investigation of the distribution of avermectins. Injected into adult Ascaris suum at doses greater than 0.1 micron per worm, it produced a dose-dependent immobilization. Fluorescent microscopy of frozen sections revealed the distribution of the probe in the whole nematode. Staining of collagenase-isolated muscle cells was studied using bath application of bodipy ivermectin. The trypan-blue quenching technique showed that the ivermectin probe was located in the outer monolayer of the muscle membrane. The cytoplasm was not stained. The interpretation of these observations is discussed in view of the known lipophilic nature of avermectins. Staining of the muscle membrane and nerve cord is consistent with the view that avermectins act at these sites. The significance of the hypodermal and lateral line staining is also discussed.

Animals↗

PubMed1992

Effect of starvation or restriction on self-selection of macronutrients in rats.

Two models of food deprivation were used to study feeding behavior: starvation and dietary restriction. Rats starved for 3 days had decreased protein intake during the first 2 days of refeeding followed by increased carbohydrate consumption compared to controls. During refeeding, total intake was initially low compared to controls. In a second starvation study of similar design, brain tissues [raphe, ventromedial hypothalamus (VMH)] and sera were collected for analysis before refeeding and on day 2 of refeeding. Starved and starved-refed rats had increased serum beta-hydroxybutyrate versus controls. In rats restricted for 5 days (5 g/day), total food intake was increased immediately and was characterized primarily by carbohydrate intake. Serotonin levels in the raphe were decreased in restricted rats and 5-hydroxyindole acetic acid (5-HIAA) increased in restricted-refed rats. Restriction caused an increase in blood levels of beta-hydroxybutyrate and a decrease in insulin and glucose compared to controls. Fat selection remained low throughout all studies. The data suggest that starvation and food restriction elicit different patterns of macronutrient selection upon refeeding.

3-Hydroxybutyric Acid↗

PubMed1992

An anorectic agent from adipose tissue of overfed rats: effects on feeding behavior.

Parabiosis and blood-transfer studies with rodents suggest the existence of humoral factors capable of affecting energy balance. The nature and origin of these factors is undetermined. Aqueous extracts of adipose tissue from overfed rats significantly reduce food intake when administered intraperitoneally (IP) or intracerebroventricularly (ICV). We term the agent(s) responsible for this effect adipose satiety factor (ASF). A single IP dose of ASF, equivalent to 44 mg crude protein, suppresses cumulative food intake for over 12 h. ASF, prepared using a combination of adipose tissue from obese Zucker rats and overfed rats, is more potent per unit of protein than ASF prepared exclusively using adipose tissue from overfed rats. A single ICV dose of this hybrid preparation, equivalent to 14.6 micrograms of crude protein, suppresses cumulative food intake by 40% for up to 48 h. By ultrafiltration, the molecular weight associated with maximal ASF activity is between 30 and 100 kilodaltons (kDa). The behavioral specificity of ASF-induced anorexia is demonstrated using meal pattern, taste aversion, and differential starvation paradigms.

Adipose Tissue↗

PubMed1992

Novel approach to diet design for determining macronutrient preference.

Previous studies indicate that rats fed a saturated vs. unsaturated fat consume more of a high-protein/low-carbohydrate and less of a low-protein/high-carbohydrate diet. Present studies were conducted to determine whether saturated-fat-fed rats are preferring protein or avoiding carbohydrate. Three combinations of diets were prepared in which one macronutrient was held constant and two covaried: 1) high protein/low carbohydrate and low protein/high carbohydrate, 2) high fat/low carbohydrate and low fat/high carbohydrate, and 3) high fat/low protein and low fat/high protein. Male Sprague-Dawley rats (75-99 g) were fed either 34% tallow (n = 30) or corn oil (n = 30) diets for 4 days. These diets were removed and one third of each group was given one of the diet combinations. Rats previously fed tallow consumed more high-protein/low-carbohydrate and low-carbohydrate/high-fat diets and less high-carbohydrate/low-fat diet than controls previously fed corn oil. These data suggest that tallow-fed animals are avoiding carbohydrate rather than preferring protein.

Animals↗

PubMed1992

Stability of the circadian alteration in lung function in asthma.

Although studies on pharmacologic interventions for nocturnal asthma are increasing, information about the long-term stability of circadian spirometric changes or bronchial responsiveness is not known. This study was undertaken to evaluate these variables in 10 patients with asthma measured quarterly during a 1-year period. We have found that the overnight decrease in peak expiratory flow rate measurements is stable (mean range, 13.8% to 16.4%) during the year, as are the quarterly 4 PM (1600-hour) and 4 AM (0400-hour) FEV1 values. The 4 PM provocative concentration of methacholine that produced a 20% fall in FEV1 (PC20) (range of geometric mean, 0.213 to 0.359 mg/ml) and the 4 AM PC20 (range, 0.057 to 0.152 mg/ml) for the group were also relatively stable. Individual variation was higher for the PC20 values than for the FEV1. We concluded that during a 1-year period, without acute respiratory events, (1) the overnight decrement in peak expiratory flow rate and the 4 AM and 4 PM FEV1 values were constant and (2) bronchial responsiveness demonstrated some individual variability, but for the group, it remained stable.

Adult↗

PubMed1992

Somatostatin and growth hormone-releasing factor release from Zucker rat hypothalamic tissue.

Plasma somatotropin (ST) levels are depressed in the genetically obese Zucker rat compared to those of their littermates. It is believed that this defect is associated with one or both of the hypothalamic neuropeptides that control ST release: growth hormone releasing factor (GRF) and somatostatin (SS). The mechanism by which SS and GRF neuropeptides are regulated remains uncertain. The objective of this study was to examine the effect of 2 deoxy-glucose (2DG), isoproterenol (ISO), tryptophan (TRP), and 5HT on SS and GRF release in hypothalamic tissue from lean and obese Zucker rats. An in vitro perifusion system was established to examine the release of SS and GRF from perifused hypothalami taken from 8- and 12-week-old Zucker rats under basal conditions and in response to 2DG, ISO, TRP, 5HT, and KCl administration. Hypothalami were perifused with Dulbecco's modified eagle's medium continuously at 37 degrees C for 5 h at a flow rate of 100 ml/min. ISO and 2DG significantly (p < 0.05) increased SS levels from the obese rat, but no effect was observed from the lean littermate. GRF was not affected by 2DG or ISO in either genotypes. TRP and 5HT failed to affect SS or GRF release in lean or obese Zucker rats. It is proposed that the obese Zucker rat is more sensitive to glucose deprivation and to beta-adrenergic stimulation of SS release than the lean littermate.

Aging↗

PubMed1992

On the distribution of a fluorescent ivermectin probe (4" 5,7 dimethyl-bodipy proprionylivermectin) in Ascaris membranes.

The distribution of the fluorescent ivermectin derivative (4" 5,7 dimethyl bodipy proprionylivermectin, referred to here as bodipy ivermectin) was studied in muscle vesicle membranes from the parasite Ascaris suum. Incubation in bodipy ivermectin, at concentrations greater than 1 ng/ml, produced a dose-dependent fluorescence in the vesicles. The level of fluorescence was not depressed (but increased) by prior incubation with 1 microM unlabelled ivermectin. This observation suggested that most of the bodipy ivermectin was free in the lipid phase of the membrane and not associated with a receptor. The trypan blue quenching technique showed that the bodipy ivermectin did not cross the membrane bilayer but remained in the outer monolayer. Lateral mobility of the probe in the membrane was studied using the fluorescence recovery after photobleaching (FRAP) technique. The lateral diffusion coefficient (DL) was 14.0 x 10(-10) cm2/s which was nearly three times faster than the lipid probe octadecanoyl-aminofluorescein in membranes from the same preparations; only 46% of the probe was mobile, showing that within a 1.2 microns radius the distribution of the bodipy ivermectin in the membrane was not homogeneous. These observations are used to suggest that: the site of action of ivermectin is located in the outer monolayer of the membrane (possibly on the Cl- channel); and that the speed of onset of action in isolated membrane preparations may be limited by diffusion in the membrane.

Animals↗

PubMed1992

The effect of dietary fat on diet selection may involve central serotonin.

Rats consuming a diet of 34% tallow select more protein and less carbohydrate than rats fed either 5% corn oil or tallow or 34% corn oil (25). To examine potential mechanism(s) of this phenomenon, we fed rats diets containing either tallow or corn oil at levels of 5 or 34% for 2 days. Sera were analyzed, and rats fed 34% tallow had higher serum insulin compared with those fed 34% corn oil. In a second experiment, rats were fed either 34% corn oil or tallow for 2 days. Brain tissues were analyzed, and rats fed 34% tallow had elevated serotonin in the raphe area compared with those fed 34% corn oil. In a third experiment, rats were fed either 34% corn oil or tallow for 2 days and then given dl-fenfluramine before diet selection. Fenfluramine depressed food intake to a greater degree in rats fed 34% tallow compared with those fed corn oil. These findings suggest that the diet selection behavior observed in tallow-fed rats may be mediated by a central serotonin system.

Animals↗

PubMed1992

Tracheal smooth muscle responses to substance P and neurokinin A in the piglet.

The tachykinins substance P (SP) and neurokinin A (NKA) have been shown to induce airway smooth muscle contraction in mature animals, and the enzyme neutral endopeptidase (NEP) modulates this effect. We evaluated maturation of SP- and NKA-induced tracheal smooth muscle contraction and modulation of their effects by NEP in anesthetized, paralyzed, and artificially ventilated piglets less than 4 days, 2-3 wk, and 10 wk of age. Tracheal smooth muscle tension was measured in vivo from an open tracheal segment by use of a force transducer. Intravenous SP caused a dose-dependent increase in tracheal tension in all three age groups; however, the response in less than 4-day-old piglets was significantly weaker than in 2- to 3- and 10-wk-old piglets. NKA caused a dose-dependent increase in tracheal tension only in 2- to 3- and 10-wk-old piglets. The response of tracheal tension to NKA was weaker than the response to SP in all age groups. Atropine (2 mg/kg) significantly diminished the responses of tracheal tension to SP and NKA, indicating a cholinergic contribution to these responses at all ages. Intravenous thiorphan, a known NEP inhibitor, potentiated the effects of SP only in 2- to 3- and 10-wk-old piglets and did not affect the response of tracheal tension to NKA at any age. Biochemical analyses demonstrated a significant increase in tracheal NEP activity in comparably aged piglets over the first 10 wk of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Biochemical and cytochemical studies of preadipocyte differentiation in serum-free culture of porcine stromal-vascular cells: interaction of dexamethasone and growth hormone.

Stromal-vascular cells from adipose tissue of pigs 5-7 days of age were grown in serum for 2-3 days and switched to serum-free (insulin, transferrin and selenium) conditions +/- test hormones for 6-7 days. The interaction of dexamethasone (DEX) and human growth hormone (hGH) was evaluated since glucocorticoids augment and hGH antagonizes the effect of insulin. Low levels (1-10 nM) of DEX with insulin doubled (p less than 0.05) specific activity of glycerol phosphate dehydrogenase (GPDH) and doubled (p less than 0.05) the number of detectable fat cells relative to insulin alone. DEX with insulin enhanced the morphological differentiation of preadipocytes and markedly increased fat cell cluster numbers in the presence of hGH. Furthermore, 1-10 nM of DEX partially blocked (p greater than 0.05) the inhibitory effect of 10 nM hGH on GPDH activity, but 1-100 nM DEX had no effect (p greater than 0.05) on the ability of hGH to compromise lipid deposition. DEX alone (no insulin or hGH) induced the appearance of esterase-reactive but lipid-free cells. Cells with these characteristics were increased in number by DEX in the presence of hGH but were nearly absent in the presence of insulin and DEX. Therefore, transient exposure to GH in vivo may have no permanent effect on adipose tissue development in the continued presence of glucocorticoids.

Adipose Tissue↗

PubMed1992

Overnight theophylline concentrations and effects on sleep and lung function in chronic obstructive pulmonary disease.

Circadian alterations in lung function occur in respiratory disorders, with the nadir during the sleep-related hours. Higher therapeutic serum theophylline concentrations (STC) during the night have been shown to improve lung function in reversible airway disease. To determine what effect higher nocturnal STC would have in patients with chronic obstructive pulmonary disease (COPD) on overnight lung function, oxygen saturation, and sleep quality, two different theophylline products were used to give higher or lower STC during the night. We found that with a higher STC (15.0 +/- 1.0 versus 11.0 +/- 1.0 micrograms/ml, p = 0.005) at 7:00 A.M., the overnight changes in FEV1 (+7.4 +/- 5.7% versus -18.9 +/- 7.9%, respectively) and FVC (+1.8 +/- 7.5% versus -17.2 +/- 3.9%, respectively) were significantly better. However, there was no apparent effect on oxygen saturation (mean sleep values for higher STC were 85.3 +/- 1.2%, and for lower STC they were 86.5 +/- 0.8%). The higher STC did not adversely affect sleep latency, sleep efficiency, or sleep staging. We conclude that a higher therapeutic STC during sleep will improve lung function without altering oxygen saturation in patients with COPD. In this group of patients, the higher STC did not interfere with sleep characteristics.

Administration, Oral↗

PubMed1992

Spectrum of corticosteroid sensitivity in nocturnal asthma.

The nocturnal worsening of asthma is a common problem, and the contribution of inflammation to its pathogenesis remains unclear. We investigated the responses of 11 asthmatic subjects to overnight intravenous infusion of hydrocortisone. Prior to the study, all the subjects demonstrated clinically stable daytime asthma but persistent nocturnal worsening of spirometry. As a group, their overnight decrement in FEV1 improved from 46 +/- 4% at baseline to 12 +/- 3% (p less than 0.001) after steroid infusion. Nine of the 11 subjects demonstrated individual improvement in their overnight decrements in FEV1 of greater than 40%. The mean improvement between baseline and steroid infusion nights was 67 +/- 11%. A spectrum of response was evident, and only four of the subjects reached the normal circadian variability in overnight FEV1 measurements of less than 8%. We conclude that the nocturnal worsening of asthma often has a significant corticosteroid-sensitive component that may be both dose- and time-dependent.

Asthma↗

PubMed1992

Risk factors for the degradation of lung elastic fibers in the ventilated neonate. Implications for impaired lung development in bronchopulmonary dysplasia.

In order to evaluate the risk for proteolytic destruction of lung parenchymal elastic fibers in ventilated premature infants, the concentrations of elastase were determined in tracheal aspirates of 65 infants from whom we obtained a total of 327 sequential samples. Elastase was detected at least once in 39 of the 65 infants studied. Eleven of these infants were ventilated with greater than 60% oxygen for greater than 5 days. In 19 infants, the presence of elastase was associated with positive bacterial and/or viral cultures and/or elevated ratios (greater than 0.22) of immature neutrophils to total neutrophils. Elastase was not detected in the lung secretions of 26 infants ventilated with greater than 60% oxygen for less than 3 days, suggesting minimal risk for elastic fiber destruction in the intubated infant who neither has pneumonia nor requires prolonged hyperoxic ventilation. The risk for elastic fiber destruction was further evaluated by analyzing sequential urine and tracheal aspirate samples for the presence of an elastolytic degradation product of elastin (desmosine). The biochemical data indicated a potential risk for proteolytic destruction of elastic fibers in association with infection and/or prolonged hyperoxic exposure. In addition, autopsy specimens obtained from three of the infants revealed structurally abnormal lung parenchymal elastic fibers. Because elastic fibers are believed to provide the structural support for alveolar septal development, proteolytic degradation of these fibers may be a significant factor in the impaired lung development that occurs in infants with bronchopulmonary dysplasia.

Bronchopulmonary Dysplasia↗

PubMed1992

Timing of prednisone and alterations of airways inflammation in nocturnal asthma.

Asthmatic subjects prone to nocturnal worsening demonstrate overnight recruitment of inflammatory cells into the airways. The influence of dose timing on the ability of corticosteroids to block circadian recruitment of inflammatory cells into asthmatic airways and attenuate the nocturnal worsening of asthma is unclear. In a double-blind, placebo-controlled, crossover design, we evaluated the response of seven asthmatic subjects with respect to overnight spirometry, blood eosinophil counts, and bronchoalveolar lavage cytology to a single variably timed 50 mg oral dose of prednisone given at 0800, 1500, or 2000 h. Compared to placebo, a single prednisone dose at 1500 h resulted in a reduction in the overnight percentage fall in FEV1 (-28.2 +/- 7.3 versus -10.4 +/- 4.5%, p = 0.04) and improvement in the 0400 h FEV1 (2.53 +/- 0.38 versus 3.43 +/- 0.38 L, p = 0.03). In contrast, neither a 0800 nor 2000 h prednisone dose compared to placebo resulted in overnight spirometric improvement. Also following the 1500 h prednisone dose, blood eosinophil counts were significantly reduced at both 2000 and 0400 h. Lastly, the 1500 h dosing resulted in a pan-cellular reduction in bronchoalveolar lavage cytology (p < or = to 0.05 for all cell lines compared to placebo), but neither alternative dose schedule significantly reduced any cell line. Our data support the relevance of timing of prednisone dose in altering the inflammatory milieu and spirometric decline associated with nocturnal worsening of asthma.

Adult↗

PubMed1992

Alae nasi activation in preterm infants during oral feeding.

Preterm infants may demonstrate impaired ventilation during oral feeding with resultant hypoxemia and hypercarbia. This study was designed to determine whether infants activate a representative upper airway muscle, the ala nasi, in response to these ventilatory changes. Ten preterm infants (postconceptional age at study 35 +/- 4 wk, weight 2.2 +/- 0.1 kg) were studied during a control period, continuous feeding, subsequent intermittent feeding, and a period of nonnutritive sucking. Nasal airflow was measured with a pneumotachometer to quantify minute ventilation. The alae nasi electromyogram (EMGAN) was recorded with surface electrodes, and sucking pressure was detected by a catheter in the feeding nipple. End-tidal CO2 and O2 saturation were also recorded during each period. The percentage of breaths associated with EMGAN activity increased from 41 +/- 13% during the control period to 95 +/- 5% and 93 +/- 7% during continuous and intermittent sucking, respectively (p < 0.05). Eighty-seven +/- 5% of EMGAN activity occurred during inspiration. During continuous and intermittent sucking, the amplitude of EMGAN activity also increased (6.8 +/- 5.2 and 6.7 +/- 4.0 arbitrary units/breath, respectively) compared with the control period (2.4 +/- 2.8 units/breath, p < 0.05). In association with the increase in EMGAN activity, O2 saturation fell from 98 +/- 1% in the control period to 95 +/- 1% during both continuous and intermittent feeding (p < 0.05), and minute ventilation fell from 274 +/- 80 mL/min/kg during the control period to 190 +/- 81 and 208 +/- 57 mL/min/kg during continuous and intermittent feeding, respectively (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Dioxide↗

PubMed1992

Voltage-activated currents in somatic muscle of the nematode parasite Ascaris suum.

1. Voltage-activated currents in cell bodies of the somatic muscle cells of Ascaris suum were studied using a two-microelectrode voltage-clamp technique. Cells recorded from had resting membrane potentials around -35 mV and had input conductances in the range 1-10 microS. 2. In cells bathed in artificial perienteric fluid, depolarizing steps from a holding potential of -35 mV elicited outward currents at a threshold of -15 mV. These currents had inwardly directed inflections on the rising phase, suggesting the presence of more than one current. Hyperpolarizing steps did not activate current. 3. Tetraethylammonium (TEA+, 69 mmol l-1) blocked the outward currents and allowed a voltage-dependent inactivating Ca2+ current to be observed. The peak current-voltage relationship was U-shaped with a threshold around -15 mV and peak at +5 mV. The reversal potential of the Ca2+ current was estimated by extrapolation to be +45 mV. 4. The permeability of the voltage-activated outward currents was studied by examining reversal potentials of tail currents. The reversal potentials were linearly dependent on the logarithm of the extracellular potassium concentration if extracellular [K+] was greater than 10 mmol l-1. The Na+/K+ permeability ratio of the currents was 0.04. 5. Inactivation, seen as a decline following the peak of the K+ current, was produced by maintained depolarization. The recovery from inactivation was complex and could be described by the sum of two exponentials with time constants of 0.67 s and 20.1 s. Steady-state inactivation of the K+ currents was observed at a range of holding potentials. Only a proportion (34%) of the total K+ current was inactivated by holding potentials more positive than -20 mV. 6. Extracellular application of 5 mmol l-1 4-aminopyridine (4-AP) selectively abolished an early fast component of the K+ current (the peak). The 4-AP-sensitive current decayed quickly with a time constant of around 10 ms; a Boltzmann fit to its activation curve had a half-maximal activation voltage of +14 mV and a 'slope' of 10.5 mV. The 4-AP-resistant current decayed with a time constant of around 1 s; a Boltzmann fit to its activation curve had a half-maximal activation voltage of +29 mV and a 'slope' of 12 mV. 7. Depolarization activates a Ca2+ current and two K+ currents: the K+ currents were separated into lower-threshold, fast-inactivating (Ia-like) and higher-threshold, slowly inactivating (Ik-like) currents.

Aminopyridines↗

PubMed1992

Norepinephrine inhibits rat pre-adipocyte proliferation.

Hormonal and neural status are major determinants for cellular growth. The purpose of this study was to assess the influence of the adrenergic hormones on pre-adipocyte growth in primary cell culture. Stromal-vascular cells were obtained from the inguinal pad of young rats and grown in culture for two weeks. Cells were exposed to norepinephrine (NE) during the proliferative phase of growth, labelled by [3H]-thymidine incorporation and then placed on a differentiation promoting medium. Adipocytes and stromal cells were separated using a density gradient, and [3H]-thymidine content was determined for both cell types. NE reduced [3H]-thymidine uptake indicating a reduction in pre-adipocyte proliferation. NE-induced inhibition of pre-adipocyte growth was blocked by the presence of propranolol, whereas phenoxybenzamine had no effect, thereby suggesting that NE-inhibition is through beta-adrenoceptors. Pre-adipocytes were treated with NE for varying lengths of time to investigate whether cells were desensitized to chronic beta-adrenergic stimulation. In addition, adenosine deaminase (ADA) was also applied to eliminate adenosine which may accumulate during NE stimulation. Neither the duration of NE exposure nor ADA treatment affected adrenergic control of adipocyte growth. These studies indicate that NE reduces pre-adipocyte proliferation and therefore may be an important negative regulatory component of adipocyte growth.

Adenosine Deaminase↗