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At least 811 records · Page 45Linked to original sources

PubMed1992

A novel hypothalamic-dispersed pituitary co-perifusion model for the study of growth hormone secretion.

This study presents a novel, in vitro, hypothalamic-dispersed pituitary co-perifusion system (HPPS) developed to examine the influence of the hypothalamus on pituitary growth hormone (GH) secretion in a controlled environment. In this perifusion system, dispersed rat pituitary cells were loaded onto Biogel P-2 (P-2) beads in a 0.5-ml plexiglas chamber and were submerged in a 37 degrees C water bath. After stabilization, two hypothalami were placed into each chamber on a thin layer of P-2 beads and the chamber was re-equilibrated. To test the system, pituitary cells were stimulated either directly with growth hormone-releasing factor (GRF) or indirectly via the hypothalamus, with clonidine, an alpha 2-adrenergic (alpha 2) receptor agonist. Perifusion of HPPS or pituitary cells with GRF (40 ng/ml) induced a substantial endogenous GH surge. Clonidine (2 x 10(-8) M) treatment stimulated a GH surge in HPPS chambers, but not in chambers containing only pituitary cells. Thus, somatotrophs respond to hypothalamic factors released in response to clonidine and not directly to alpha 2 stimulation. To determine if the components involved in GH feedback are present in the perifusion system, HPPS chambers were sequentially perifused with hGH, clonidine, and GRF. hGH pretreatment suppressed the clonidine but not the GRF-induced GH surge(s) observed in chambers perifused with clonidine and GRF only. In chambers only containing pituitary cells, GH was only increased in response to GRF when sequentially perifused with all three substances. This study demonstrates the dynamic interaction between the hypothalamus and pituitary in the regulation of GH secretion in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1980

Early postnatal development of wakefulness-sleep cycle and neuronal responsiveness: a multiunit activity study on freely moving newborn rat.

The development of the wakefulness-sleep cycle and neuronal responsiveness was studied on freely moving 1-, 3-, 5- and 7-day-old rats. Semimicroelectrodes were implanted under ether anaesthesia for multiunit activity (MUA) recording from the mesencephalic reticular formation (MRF) and basal forebrain area (FB). Following recovery from surgery and between the recording sessions pups were put back to the nest to be fed by their mothers. In a temperature-controlled environment continous MUA records were made between 16:00-18:00 and 19:00-21:00 h. In the MRF and FB the MUA was high during wakefulness, it decreased to a stable low level in quiet sleep and appeared to reach the highest values in paradoxical sleep. Neurone populations in the MRF and FB responded to somatosensory (air puffs), visual (flicker) and acoustic (1100 Hz) stimulation by a significant increase of MUA from the first day of life. In the MRF the rate of responsiveness increased during the first postnatal week; however, MUA responses to different stimuli exhibited different developmental time-courses. A high rate of responsiveness to each stimulus was characteristic of FB units. This neonatal 'supersensitivity' tended to decrease with age and the time-course of developmental changes proved to be modality-dependent.

Acoustic Stimulation↗

PubMed1984

A serum-free defined medium for retinal pigment epithelial cells.

Human and bovine RPE cells underwent changes in morphology and culture doubling times when passaged in serum-supplemented medium (CM). Furthermore, late passage human RPE cells subcultured in CM medium increased synthesis of three acidic, 43 000-63 000 D proteins. In order to provide a controlled environment for the study of RPE cells in vitro, we have developed a method for growing human and bovine RPE in a serum-free defined medium (DM). RPE cells grown in DM required a 24 h pretreatment with CM to allow the cells to attach and spread on the substrate. Cells grown in DM retained an epithelioid morphology, a stable culture doubling time, and similar 2-D PAGE patterns through several subculturings.

Animals↗

PubMed1996

Capillary isoelectric focusing and sodium dodecyl sulfate-capillary gel electrophoresis of recombinant humanized monoclonal antibody HER2.

Capillary isoelectric focusing (cIEF) and IEF of recombinant humanized monoclonal antibody HER2 (rhuMAbHER2) show five charged isoforms with estimated pI values ranging from 8.6-9.1. The cIEF assay demonstrated good precision with relative standard deviations (R.S.D.) 0.7-3.7% and 0.4-4.2% for intra and interassay analysis, respectively. The method was linear for the area of the main peak over the concentration range 2-250 micrograms/ml with a Pearson correlation coefficient > 0.99. The limit of detection for the main peak was determined to be 2 ppm. With both sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) and SDS-polyacrylamide gel electrophoresis, the nonreduced rhuMAbHER2 migrated as a single major peak with minor peaks in the aggregate and clip regions. After reduction, the electropherogram and the slab gel showed the expected heavy chain and light chain fragments with minor peaks in the aggregate and clip regions. The SDS-CGE assay showed good precision with R.S.D. values of 0.1-7.8% and 0.1-8.1% for intra and interassay analysis, respectively. The Pearson correlation coefficient for the area of the main peak was > 0.99 demonstrating linearity for the concentration range 0.5-500 micrograms/ml. The limit of detection for intact rhuMAbHER2 was determined to be 0.5 ppm. The data presented demonstrates the feasibility of replacing the slab gel techniques with capillary electrophoresis in a quality control environment.

Antibodies, Monoclonal↗

PubMed1988

Measured energy expenditure in critically ill infants and young children.

Technological limitations have impeded accurate energy expenditure assessment in critically ill infants and young children. Instead, a predicted energy expenditure (PEE) is derived based on weight, heat loss, activity, growth requirements, and degree of stress. This study compared actual measured energy expenditure (MEE) with conventional predicted values in 20 critically ill infants and children using a validated metabolic cart designed for use in this age group. All patients were studied either within 4 days of major surgery or during an acute disease process necessitating intensive care. All were severely stressed clinically and were studied while mechanically ventilated in a temperature-controlled environment. The study interval ranged from 1 to 12 hr and averaged 4 hr after a stabilization period of 30 min. The mean MEE was significantly lower than the mean PEE (52.2 +/- 16 kcal/kg/day vs 101.8 +/- 17 kcal/kg/day, P less than 0.001) with a mean MEE/PEE of 52.6 +/- 17% (range 26 to 92%). In a subgroup of 7 paralyzed patients, the mean MEE was significantly lower than in the 13 nonparalyzed patients when compared with PEE and predicted basal metabolic rate (PBMR). The coefficient of variance, conventionally recognized to be approximately 15% for PEE, averaged 6.35% for MEE in this study. These data indicate that if PEE is used as the sole guide for caloric repletion in the stressed infant or child, these patients will be substantially overfed.

Basal Metabolism↗

PubMed1983

New approaches to the study of human dystrophic muscle cells in culture.

Tissue culture provides a system for studying the growth and differentiation of muscle cells in a controlled environment. Several studies have been carried out on diseased muscle cells in culture in attempts to elucidate the aetiology of Duchenne muscular dystrophy (DMD) but the results were equivocal. Work in our laboratory in recent years has yielded an improved method for preparing primary muscle cell cultures from dissociated biopsies which permits the morphological and biochemical evaluation of these cultures at all stages of growth and development. Our results have shown abnormalities in cell behaviour, ultrastructure and creatine kinase synthesis. The background to these studies is reviewed. Recently we have developed a cell cloning procedure that allows the accumulation of a large number of cells from a single selected cell. We can with this technique monitor quantitative and qualitative cellular and cytochemical differences between individual cell types without the ambiguities inherent in the use of mixed cell populations. The results obtained with 4 different clonal preparations derived from dystrophic muscle have shown that a number of specific features were expressed by each of the 4 clones with respect to their growth pattern, ultrastructure, synthesis of muscle specific protein and cell surface antigen. These findings clearly illustrate the potential of these cloning procedures for studying the genetic expression of homogeneous cell populations derived from normal adult human muscle and patients with X-linked muscle disease.

Cells, Cultured↗

PubMed1989

The rat urinary bladder: vasoactivity and macromolecular leakage in a new model.

An in vivo model of the rat urinary bladder microcirculation has been developed and microcirculatory responses to agents which produce vasoconstriction, vasodilation, and macromolecular leakage have been characterized. The urinary bladder of anesthetized female Sprague-Dawley rats is exteriorized and positioned in a tissue bath with a single stay suture which does not penetrate the lumen of the bladder. All blood vessels and nerves from the animal remain intact. The tissue bath is filled with Krebs solution which is monitored and maintained at a temperature of 36 +/- 0.5 degrees and a pH of 7.4 +/- 0.5. In vivo television microscopy is used to monitor vascular diameter and flow changes and isothiocyanate-tagged bovine serum albumin fluorescence is used as an index of macromolecular leakage. Norepinephrine (10(-6) M) caused a statistically significant decrease in vascular diameters of both arterioles and venules while sodium nitroprusside (10(-7) M) significantly increased arteriolar and venular diameters, histamine (10(-4) M) caused no change in venular diameters but did induce a significant macromolecular leak from those vessels. Compound 48/80 (1 and 10 micrograms/ml) induced a significant dose-dependent macromolecular leakage from venules. However, only with the 10 micrograms/ml dose was there visually detectable mast cell degranulation. It is concluded that this rat urinary bladder model provides a stable, reproducible model of a smooth muscle microcirculatory bed in a controlled environment, which responds similarly to other microcirculations.

Animals↗

PubMedDate not supplied

Day-night difference in the preferred ambient temperature of human subjects.

To investigate the existence of a day-night difference in thermal preference, 32 college students (16 male, 16 female) were asked to indicate a threshold of discomfort in a climate-controlled environment. The experiment was performed at two distinct times of day that corresponded to the peaks and troughs of the subject's circadian rhythm of body temperature. Males, but not females, felt comfortable at a higher ambient temperature during the trough than during the peak of the body temperature rhythm. These data support the hypothesis (derived from animal studies) that behavioral thermoregulation opposes the circadian rhythm of body temperature.

Adult↗

PubMed1986

The effects of sulindac and its metabolites on acute stress-induced gastric ulcers in rats.

Rats were given a single intragastric administration of the prodrug sulindac (4.0 mg/kg) or its sulfide (1.0, 2.0, 4.0, or 8.0 mg/kg) or sulfone (1.0, 2.0, 4.0, or 8.0 mg/kg) metabolites and were then subjected to acute stress in the form of immobilization for 3 hr in a cold environment. Control rats received an equal volume of propylene glycol vehicle or nothing po. Other rats received 200 mg/kg acetylsalicylic acid (ASA) with or without stress, to compare the gastrointestinal effects of sulindac metabolites with those of a known non-steroidal anti-inflammatory agent. The sulfide metabolite exacerbated stress-induced gastric glandular ulcer incidence and severity in a dose-related manner relative to all groups except the ASA-stress group, which exhibited the greatest amount of gastric damage. The sulfone metabolite did not potentiate ulcer incidence or severity beyond control (stress only) levels at lower doses. However, at 4.0 and 8.0 mg/kg, the observed ulceration was greater than that seen in stressed but otherwise untreated animals. Sulindac, vehicle, and otherwise untreated rats exhibited a similar degree of stress-induced gastric damage. It appears that the prodrug does not significantly enhance stress-related gut disease, but that the active sulfide metabolite does. Although the clinical literature suggests that the sulfone metabolite is inactive, the present results suggest otherwise. While this metabolite did not, by itself, induce gastric damage at higher doses, sulfone did exacerbate stress ulcer formation. This is the only report of which we are aware, indicating a possible toxic effect of the sulfone metabolite.

Administration, Oral↗

PubMed1982

Chronic exposure to caffeine during early development modifies spatial behavior in juvenile jewel fish schools.

Thirty sibling African jewel fish (Hemichromis bimaculatus) were either chronically exposed to caffeine between 50 to 100 days of age (at a concentration of 14 mg/l) or reared without drug in a control environment. After caffeine was withdrawn, fish in each group were videotaped for 30 minutes while schooling in a large tank. From the video record, mean distances and coefficients of variation of spacing were computed for each fish and its 1st to 9th nearest neighbors in all observations. Spacing distances were nearly identical for the two groups, but the caffeine fish exhibited much more variability in their spacing behavior (p less than 0.00001). This study demonstrates an effect on behavior of moderate caffeine levels present throughout the early developmental period, and illustrates a quantitative method to test for such effects.

Animals↗

PubMed1985

Effect of PMSG dosage on the reproductive performance of adult ewes and ewe lambs bred at a progestagen-PMSG synchronized estrus.

The effect of dose of pregnant mares' serum gonadotropin (PMSG) on the reproductive performance of adult ewes and ewe lambs and lamb survival at birth after treatment with fluorogestone acetate (FGA)-impregnated intravaginal sponges and PMSG (250 IU or 500 IU) to synchronize estrus was evaluated. Ewes were exposed to rams for breeding at the synchronized and subsequent estrous cycles. The flock, comprised of three synthetic strains and two control breeds, was maintained in a controlled environment and exposed to an artificial light regimen which alternated at 4-mo intervals from 16h of light daily to 9h of light daily. Trials were conducted during January, May and September at the end of a 9-h daylength cycle. Adult ewes were bred in May and 8 mo later in January. Ewe lambs were bred in September at 6.5 to 7.5 mo of age. The overall reproductive performance of the adult ewes was similar at the two breedings: fertility approximately 90%, prolificacy approximately 2.7, fecundity approximately 240% and lambs born alive approximately 2.4. Dosage of PMSG had no effect. Reproductive performance of ewe lambs was lower and there was a strain x treatment interaction, suggesting greater variability in response. The results indicate there is no advantage to using a higher dose of PMSG in ewes with a natural relatively high fecundity. Moreover, the use of the artificial photoperiod appears to overcome the natural seasonal variation in reproductive performance.

Journal Article↗

PubMed1992

Autoantibodies in pet dogs owned by patients with systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) occurs in human beings and in dogs. There is evidence to suggest that the disease is caused by a transmissible factor that may cross the species barrier. We investigated this possibility by looking for autoantibodies and serum protein abnormalities in serum samples from 15 pet dogs owned by patients with SLE and comparing results with those obtained with serum from 10 healthy dogs kept in a controlled environment and 9 dogs with autoimmune diseases. We used standard immunological assays modified for use with canine samples. Compared with the normal dogs, increased amounts of antibody to double-stranded DNA were found in serum from the SLE patients' dogs (median optical density [405 nm] = 0.117 vs 0.299; p = 0.0001), this latter amount being similar to that found in serum from the autoimmune group (0.201; p = 0.6). Abnormal serum protein electrophoresis patterns were found in samples from the autoimmune and SLE patients' dogs but not the normal dogs. These findings support the idea that exposure to common environmental factors or transmissible agents may have a role in causing SLE.

Animals↗

PubMed1988

Perifused precision-cut liver slice system for the study of hormone-regulated hepatic glucose metabolism.

A nonrecirculatory perfusion system for precision-cut rat liver slices has been developed and utilized for investigating hormone-regulated hepatic glucose metabolism. In this system, slices are cultured in a highly controlled environment and exhibit excellent retention of viability as judged by their maintenance of intracellular potassium and glycogen contents. Using this system, the complex physiological phenomenon of hormone-regulated glycogenolysis was investigated at both extra- and intracellular sites. Specifically, the sensitive responses of intracellular cyclic AMP (cAMP) production, activation of cyclic AMP-dependent protein kinase, and production of glucose upon glucagon stimulation have been measured. The maximal responses observed for these parameters were either equal to or greater than those previously reported for either isolated hepatocytes or perfused livers, demonstrating the sensitivity of this technique. Upon dose-response examination of glucagon challenge, it was observed that high doses of glucagon (greater than 16 nM) stimulate glucose production by activating the cAMP-second messenger cascade. In contrast, low doses (less than 4 nM) stimulate this process without production of intracellular cAMP or activation of cAMP-dependent protein kinase, suggesting the operation of cAMP-independent messenger. Since this system permits measurements of parameters common to many cellular processes, this methodology is suitable for addressing both pharmacological and toxicological questions.

Animals↗

PubMed1988

SCH28080 prevents omeprazole inhibition of the gastric H+/K+-ATPase.

The interaction between SCH28080 and omeprazole, two specific inhibitors of gastric H+/K+-ATPase, was investigated using gastric glands and isolated gastric membranes. For gastric glands, inhibition of acid formation by SCH28080 was not reversed by washing whereas inhibition by omeprazole was partially reversed after washing. These features are opposite to what is found with isolated membranes. However, if gastric glands were permeabilized with digitonin after exposure to the inhibitors and recovery measured as ATP-dependent acid formation or H+/K+-ATPase activity, inhibition by SCH28080 was completely reversed while inhibition by omeprazole was non-reversible. Using a procedure of pretreatment with inhibitors followed by permeabilization and assay of recovered activity, it was found that a combined treatment with SCH28080 plus omeprazole prevented the irreversible inhibition by omeprazole, i.e. acid forming capability and ATPase activity were fully recovered. In order to test the possibility that SCH28080 prevented activation of omeprazole by dissipating an acid environment, control experiments were performed with SCN, which gave equivalent dissipation of the acid gradient but did not prevent the irreversible inhibition by omeprazole. These results were confirmed in isolated gastric membranes where residual p-nitrophenylphosphatase activity was assayed following exposure of acid transporting vesicles to omeprazole. Compared to control conditions, omeprazole inhibited 48% of the phosphatase activity whereas simultaneous addition of SCH28080 reduced the inhibition to 14%. The results therefore suggest that SCH28080 selectively blocks irreversible inhibition by omeprazole and thus that these two agents interact at a common region of the luminal aspect of the gastric H+/K+-ATPase.

Adenosine Triphosphatases↗

PubMedDate not supplied

Circadian rhythms of activity in healthy young and elderly humans.

Patterns of activity of healthy adult humans were monitored in a controlled environment for several days using a wrist-mounted ambulatory activity meter. Subjects were 15 young males, 14 young females, 17 elderly males and 23 elderly females. Substantial differences in the absolute levels and patterns of daily rest and activity across age groups were observed. The elderly subjects were somewhat more active than the young subjects overall, especially in the early morning. Consistent with their increased levels of daytime activity the elderly subjects reported less sleepiness, especially in the morning, than the young volunteers. The age groups also differed significantly on all circadian parameters. The mean acrophase (peak of a sinusoid fitted to the activity rhythms) of the elderly group occurred at 1326 hr, significantly earlier than in the young group (1513 hr). The amplitude and the mesor (mean level) of the rhythms were both greater in the elderly group. It is uncertain whether these differences reflect changes in behavior that occur as a consequence of the aging process, previously-established differences in the life styles of the different populations studied, or some other factor. These findings suggest that levels and rhythms of daily activity in healthy elderly people are often well preserved and may not deteriorate as readily as had been assumed.

Adult↗

PubMed1988

Chemometric studies of the effect of toxic metals on plants: the use of response surface methodology to investigate the influence of Tl, Cd and Ag on the growth of cabbage seedlings.

The growth of cabbage seedlings at five concentrations of Cd, Tl and Ag was monitored by measuring their wet weights, root and shoot lengths after four week's growth in a controlled environment. Toxicity curves were constructed using a three factor central composite experimental design. The interaction and competition between any two metals were studied by displaying response surfaces. Ag was observed to be the most toxic, while Tl and Cd, although toxic, exhibited fairly similar effects. Analysis of variance was used to test for the significance of each of the computed parameters.

Journal Article↗

PubMed1989

Ozone flux to Picea sitchensis (Bong) Carr and Picea abies (L) Karst during short episodes and the effects of these on transpiration and photosynthesis.

Sitka spruce and Norway spruce were grown in controlled environments and then exposed to ozone (O3) for short periods as in mid-afternoon episodes experienced in the forest. For concentrations of between 20 and 300 nl litre(-1) there were linear relationships between exposure concentration and O3 uptake rates. Increasing photon flux densities increased rates of photosynthesis and transpiration, the increases being larger in actively growing than dormant seedlings. Physiological condition (dormancy or active growth), species and photon flux density were found to influence O3 flux via their effects on stomatal conductance. Exposure to 80 nl litre(-1) O3 resulted in consistent increases of stomatal conductance and there were also indications that water-use efficiency was decreased.

Journal Article↗

PubMed1990

Diminished greenness of tomato leaves exposed to ozone and post-exposure recovery of greenness.

The response to ozone (O(3)) of greenness, in terms of estimated total chlorophyll concentration (Chl), of leaves at three plant canopy levels was studied in tomato (Lycopersicon esculentum Mill.) over a 10-day period following O(3) exposure. Plants of the cultivars 'New Yorker' and 'Tiny Tim' were grown at 25/15 degrees or 30/15 degrees day/night temperatures in growth chambers and exposed to 0.00, 0.08, 0.16 or 0.24 microl litre(-1) O(3) for 7 h day(-1) for four consecutive days in controlled environment exposure chambers. Measurement of Chl in the top, middle and bottom canopy leaves with a calibrated SPAD-501 leaf greenness meter indicated that the growth temperatures tested did not significantly influence the response of Chl to O(3). Ozone-induced loss of Chl was widespread in the entire foliage canopy, including foliage which did not demonstrate visible injury. In both cultvars the Chl in leaves at all three canopy levels declined as a function of increasing O(3) concentration when measured 2, 4, 6, 8 and 10 days after the exposure period. However, the slopes for leaves in the top and middle canopies decreased with increasing time after exposure. An analysis of this apparent Chl recovery indicated that leaves in the top and middle canopies exposed to 0.16 and 0.24 microl litre(-1) increased in greenness at a rapid rate after the marked initial decline associated with O(3) treatment. The apparent recovery of the top canopy may have reflected the growth of new leaves and their inclusion in the measurements, but this was not the case for the middle canopy for which the same leaves were measured throughout the post-exposure period. Bottom canopy leaves did not demonstrate significant recovery of Chl.

Journal Article↗