New research study set to remedy learners' problems on the wards.
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Clinical Competence↗
Biomedical subjects
S Ellis
Publications and source records attributed to S Ellis.
Dose-dependent initiation of myogenesis by neurotrophic factor.
The kinetics of primary chick muscle cells in response to partially purified neurotrophic factor (NTF) were investigated. Chick muscle cells are routinely plated in the absence of NTF but in the presence of horse serum to allow cell attachment to the substratum; a maximum number of cells attaches 5-8 hr after plating, but cells do not proliferate in the absence of NTF, or do so extremely slowly. Subsequent to a routine attachment period of 6 hr, the medium is aspirated and replaced with medium containing 2-20 micrograms/ml of NTF as well as horse serum. Dose responsiveness at elevated NTF concentrations is observed only if F12 medium, supplemented with serum, insulin, transferrin, and selenium is used. In the presence of commercial F10, although supplemented with serum, dose responsiveness is not apparent at more than 2 micrograms/ml of NTF. Upon exposure to NTF, in the presence of supplemented F12 and serum, an 8-hr lag ensues; then, thymidine is incorporated at NTF dose-dependent rates by growing cell populations. The rates of incorporation into cell populations depend on the initial number of cells plated and the amount of NTF supplied. Cell counting indicates that dose-dependent proliferation of muscle cells has occurred during the first 48 hr of exposure to NTF. The specific activity of NTF is repeatedly shown to be at least 10-fold greater than unfractionated nerve extract. Shortly after 48 hr of exposure to NTF, myoblasts characteristically begin to fuse with one another, and myogenesis is visible. These studies show that the initiation of in vitro myogenesis in primary chick muscle cells depends on the amount of NTF supplied. The work also indicates a requirement for optimum medium conditions in order to detect dose-responses to NTF.
Animals↗
Carbonic anhydrase activity in skeletal muscle fiber types, axons, spindles, and capillaries of rat soleus and extensor digitorum longus muscles.
Carbonic anhydrase (CA) activities were studied in soluble extracts and cryostat sections of skeletal muscles from prepubertal and postpubertal rats. Acetazolamide inhibition was utilized to distinguish between activities of the acetazolamide-sensitive (CA I and II) and acetazolamide-resistant (CA III) forms of the enzyme. The inhibition studies indicated that fast-twitch oxidative-glycolytic muscle fibers contained both the sensitive and resistant forms of CA. Acetazolamide-sensitive activity was localized within muscle fibers, axons, myelin, and capillaries. Axoplasmic staining was restricted to subpopulations of myelinated axons in both the dorsal and ventral roots. Soleus muscles exhibited significantly greater activity of CA III than extensor digitorum longus muscles at all ages examined. CA III was richest in slow-twitch oxidative and intrafusal fibers. During puberty, soleus muscle fibers matured and converted from fast-twitch oxidative-glycolytic to slow-twitch oxidative fibers. There was a shift from the sensitive to the resistant form of CA; CA III activity increased about sevenfold. This activity peaked earlier in the muscles of female rats than male rats. These results demonstrated a complex distribution of CA isozymes in the neuromuscular system and pointed out that isozyme content depends on both the type of muscle and the age and sex of the animal.
Acetazolamide↗
Heterogeneity of rat pituitary gonadotropins on electrofocusing; differences between sexes and after castration.
Anterior pituitary extracts from intact and 4 week postcastration male and female rats were electrofocused in sucrose density gradients within the pH range 3.5-10. Column fractions were combined to cover this pH range in 0.5 pH units and assayed for LH by in vitro bioassay and RIA and for FSH by radioreceptor assay and RIA. The pH distribution of bioactive LH was altered after castration in both sexes, with the proportion of recovered activity in the alkaline pH range increasing (P less than 0.01) from 52-57% in the intact animal to 71-73% after castration. In addition, significantly more bioactivity was recovered in the pH range 7-9.5 with the male (37%) than with either of the female (diestrous, 30% or proestrous, 28%) groups (P less than 0.05). FSH receptor binding activity was located in the pH region 3.5-6.5. Significantly less receptor binding activity was recovered in the pH range 3.5-4.5 with the female groups (39% and 37% diestrous and proestrous, respectively) than the male group (61%; P less than 0.05, P less than 0.01). The distribution of immunoreactive LH and FSH was similar to that observed with the LH in vitro bioassay and FSH radioreceptor assay. It is concluded that the charge distribution of pituitary gonadotropins is altered according to the sex of the animal and after castration. These findings provide further evidence that the type of gonadotropin produced by the pituitary is under endocrine control.
Animals↗
Neurotrophic factor: characterization and partial purification.
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Ammonium Sulfate↗
The effect of level of depression on the use of visual analogue scales by normal volunteers.
1 In two separate studies, 102 normal male volunteers were screened for level of depression using the Zung Self-Rating Depression Scale (Zung, 1965). Eight high scorers and eight low scorers were selected for inclusion in each study. 2 There were marked differences in scores on the visual analogue mood scales of Bond & Lader (1974) between the high depressed (HD) and low depressed (LD) groups. 3 In the first study, subjects were given single doses of imipramine 50 mg and 100 mg, diazepam 10 mg, and placebo in a double-blind randomized crossover design with 1 week between treatments. Drug effects as assessed on visual analogue scales were significantly more marked in the LD than in the HD group, to the extent that the sedative effects of imipramine 50 mg and diazepam 10 mg were minimal or absent in the HD groups whereas these effects were clear and highly significant in the LD group. 4 In a second study, LD and HD volunteers were given more objective items to rate using visual analogue scales. Ratings of the size of each of a series of ten circles, and of the weight of a 'black box', were consistently and significantly lower in the LD than in the HD group. Significant differences between LD and HD groups were also found on a series of visual analogue scales expressing attitudes not directly related to mood. 5 It is concluded that normal volunteers with varying levels of depression cannot be considered as homogeneous in their mode of expression on visual analogue scales, and that this should be taken into account in the design and interpretation of studies involving the use of such scales.
Adolescent↗
Glucose transport across ocular barriers of the streptozotocin-diabetic rat.
The transport kinetics across the plasma-aqueous and plasma-vitreous barriers were studied in normal and long-term streptozotocin-diabetic rats, using trace amounts of [14C]-L-glucose and [3H]-3-O-methyl-D-glucose. The former is passively transported while the latter uses the same transport-facilitating system as D-glucose. Transport rates of L-glucose were significantly higher in the diabetic rats, with ocular entry rates from the plasma being increased by 69% across both barriers. Thus, the data indicate that in experimental diabetes the passive permeability of the blood-ocular barriers is significantly increased. By contrast, calculated transport rate constants for 3-O-methyl-D-glucose, when adjusted for the hyperglycemia and the increased passive glucose movement, are not altered in the diabetic animal. Nevertheless, there is actually more mass D-glucose movement due to the prevailing hyperglycemia. The present study suggests that although streptozotocin diabetes alters plasma-ocular glucose transport, there is no direct impairment of glucose carrier function. Alterations in transport occurred at both ocular barriers, suggesting that involvement is general and that both the retinal pigment epithelium and the ciliary epithelium may be affected by the diabetes. It is unknown whether the increase in passive movement is related to the prevailing hyperglycemia or to insulin deficiency or other unknown factors.
3-O-Methylglucose↗
Lectins used to prepare serum free of glycoprotein hormones for use as a matrix in radioimmunoassay.
Hormone-free serum is required for use as a matrix for standards in the radioimmunoassay of hormones. The glycoprotein hormones are difficult to remove from serum by conventional techniques. We exploited the specific binding of carbohydrates by lectins to extract glycoprotein hormones from human serum. Passing serum over Concanavalin A Sepharose efficiently removed lutropin and the beta subunit of choriogonadotropin. Wheat-Germ Lectin Sepharose completely removed these, and also follitropin and thyrotropin. The latter treatment is shown to provide a suitable matrix for standards in radioimmunoassays of the four hormones.
Blood Chemical Analysis↗
Pharmacy--health centers: assessing the public's needs.
The role of the pharmaceutical officer in the establishment of health centres is explained by Dr Shirley Ellis, regional pharmaceutical officer, East Anglian RHA. She describes the conflicts which may arise for the PhO and stresses the importance of avoiding the impression that pharmacists lose some of their independence by agreeing to practise from a health centre.
Community Health Centers↗
Development of angiotensin-induced drinking in the rat.
The suckling rat responds from birth to intraventricular angiotensin, and the drinking behavior elicited by the hormone achieves adult characteristics of reliability and sensitivity at 4--5 days of age. Additional testing of 5-day-old rats injected with a range of doses showed that the threshold dose lies between 0.1--1.0 ng, which is comparable to the adult sensitivity to intraventricular injections. The hormone also increases milk intake in neonates, but the animals choose water over milk as early as 17 days.
Angiotensin II↗
The importance of pluripotential stem cells in benzene toxicity.
Several schedules of benzene exposure were evaluated for their effects on peripheral white blood cell counts, bone marrow cellularity and transplantable colony forming units (CFU-S) in male C57 Bl/6 mice. Intermittent exposure to 4000 ppm benzene in air produced leukopenia without altering the bone marrow cellularity. This same treatment, however, decreased the number of CFU-S to 30% of control values. Uninterrupted exposure to lower levels of benzene decreased peripheral cell counts within 24 h, and later decreased marrow cellularity. Exposure of a non-dividing population of stem cells (CFU-S) to benzene for up to 24 h produced no detectable effect on the subsequent development of spleen colonies, suggesting that the effect of benzene on CFU-S occurs only after peripheral cells are depleted. These findings indicate that benzene has affects on both differentiated cells and undifferentiated stem cells. An effect on the pluripotential stem cell is an important aspect of benzene toxicity, but not its exclusive or initial site of action.
Animals↗
Comparative metabolic and cardiovascular effects of carbuterol, isoproterenol, metaproterenol and salbutamol in the baboon.
The metabolic and cardiovascular responses to two bronchiolar selective beta-adrenergic drugs, carbuterol (CAR) and salbutamol (SAL), were compared with isoproterenol (ISO) and metaproterenol (MET) in fasted, anesthetized baboons. ISO was more active than the selective beta-adrenergic drugs in elevating plasma levels of glucose, lactate, free fatty acids, insulin, and glucagon. Moreover, ISO was more active in increasing heart rate and respiratory rate and in depressing diastolic blood pressure. Although ISO was shown to have greater activity than CAR, MET, and SAL, the bronchiolar selective drugs (CAR and SAL) did produce significant changes in plasma levels of metabolic substrates and pancreatic hormones and in cardiovascular measurements at higher dose rates.
Adrenergic beta-Agonists↗
Central respiratory and circulatory effects of Gymnodinium breve toxin in anaesthetized cats.
1 In cats anaesthetized with pentobarbitone, observations were made on respiration, spontaneous and evoked diaphragmatic electromyograms, blood pressure, heart rate, indirectly-induced contractions of the anterior tibialis muscle and nictitating membrane, and electrical excitability of the inspiratory centre in the medulla oblongata.2Gymnodinium breve toxin (GBTX) was administered intravenously, intra-arterially to the brain, and intracerebroventricularly. Physiological effects were recorded while alveolar P(CO) (2) was controlled at a constant level except when changes in gas tension were made in order to measure CO(2)-ventilatory responsiveness.3 Adequate doses of GBTX given intravenously by bolus injection elicited a non-tachyphylactic reflex response triad of apnoea, hypotension and bradycardia mediated by the vagus nerves independently of arterial baroreceptor and chemoreceptor innervation.4 After vagotomy, additional amounts of GBTX (i.v.) resulted in apneustic breathing, hypertension and tachycardia. The cardiovascular effects were abolished by ganglionic blockade with hexamethonium.5 Smaller doses of GBTX were required intra-arterially and intracerebroventricularly than by the intravenous route of injection to produce respiratory irregularity and cardiovascular hyperactivity.6 Evoked motor responses, electrical excitability of the medulla oblongata and CO(2)-ventilatory responsiveness were largely spared even though GBTX caused marked disturbances in respiratory rhythmicity and cardiovascular functions.7 It is concluded that GBTX acts reflexly on vagally innervated receptors to evoke a Bezold-Jarisch effect but that the toxin further acts centrally to cause irregular breathholding and hypertension with tachycardia, leading ultimately to respiratory and circulatory failure.
Anesthesia↗
Vitamin A supplements in hemodialysis patients.
A total of 14 hemodialysis patients were followed for an average of 8.4 months after stopping oral vitamin A supplements (5,000 U daily). No change occurred in the mean vitamin A plasma levels. 11 of the 14 patients were followed for an average of 16.3 months, and no change was noted in the mean vitamin A level. Vitamin A intake does not seem to effect the plasma vitamin A level in hemodialysis patients. This is consistent with the possibility that the vitamin A levels in hemodialysis patients are increased because of an increase in retinol binding protein.
Adult↗
Modifications of benzene myelotoxicity and metabolism by phenobarbital, SKF-525A and 3-methylcholanthrene.
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Animals↗
A costly mistake?
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Attitude of Health Personnel↗
Building an identity.
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Congresses as Topic↗