Search PubMed⌕ Search

Biomedical subjects

M Callahan

Publications and source records attributed to M Callahan.

67 records · Page 4Linked to original sources
PubMed1980

Depletion of central catecholamines alters amphetamine- and fenfluramine-induced taste aversions in the rat.

Conditioned taste aversions induced by pairing the consumption of saccharin with an amphetamine injection are attenuated in rats with depletion of central catecholamines caused by intraventricular administration of 6-hydroxydopamine (6-OHDA). The hypothesis that dopamine (DA) depletion is responsible for this effect was tested. The reduction in conditioning caused by intraventricular 6-OHDA could not be duplicated either with injections of 6-OHDA into the substantia nigra (Experiment 1) or with intraventricular 6-OHDA injections in animals pretreated with desmethylimipramine (Experiment 2). Both treatments, however, produced large depletions of telencephalic DA. 6-Hydroxydopa infusions caused a preferential loss of telencephalic norepinephrine (NE) but also failed to alter taste aversion learning. It is concluded that the effect of intraventricular 6-OHDA on amphetamine-induced aversions was the result of depletion of both NE and DA. In a third experiment the generality of the effect was examined by pairing saccharin consumption with injections of the amphetamine congener fenfluramine. Depletion of both NE and DA failed to alter fenfluramine-induced aversions. Infusion of 6-OHDA into the substantia nigra, however, retarded the extinction of such an aversion. Evidence is discussed for a peripheral site of action for fenfluramine in the conditioned aversion paradigm.

Animals↗
PubMed1979

Evaluation of the non-specific effects of catecholamine and serotonin neurotoxins by injection into the medial forebrain bundle of the rat.

Low doses of 6-hydroxydopamine (6-OHDA), 5,6-dihydroxytryptamine (5,6-DHT) and 5,7-dihydroxytryptamine (5,7-DHT) that have previously been shown to produce behavioral change following intracerebral infusion were injected into the medial forebrain bundle of the rat. This site contains serotonin (5-HT), norepinephrine (NE), and dopamine (DA) fibers whose anatomical locations have been described. Damage to these fiber systems was quantified by measuring depletion of telencephalic 5-HT, NE and DA. The effects of infusions of 6-OHDA, 5,6-DHT and 5,7-DHT were compared to the effects of unequivocally non-specific electrolytic lesions and copper sulfate infusions. Survival time was varied to evaluate the amount of regeneration that could be expected over periods from 8 to 60 days. Amine levels were found to be stable over the time period examined. With the doses used, evidence was found to support the position that non-specific damage caused by general cytotoxic effects of 6-OHDA and 5,7-DHT is minimized sufficiently to permit the acquisition of useful data on the function of central catecholamine and indoleamine systems.

5,6-Dihydroxytryptamine↗
PubMed1979

Effects of goldthioglucose lesions on central catecholamine levels in the mouse.

Male and female C57 B1/6J mice were injected with goldthioglucose (GTG) to induce an obesity syndrome. Significant increases in body weight were inversely correlated with pituitary dopamine (DA) levels. Significant reductions in hypothalamic norepinephrine (NE) and DA were also noted; however, these reductions did not appear to be related to body weight gain. The GTG injections did not produce any significant alterations in telencephalic NE or DA. The damage to catecholamine neurons is discussed in relation to the endocrine abnormalities of the GTG mouse and some current hypotheses on the control of food intake.

Animals↗
PubMed1979

Binding of the Cain quinolinium, NSC 113089, to rat tissue lipid extracts.

The binding characteristics of the cancer chemotherapeutic Cain's quinolinium 6-amino-1-ethyl-4-[p-[[p-[(1-ethylpyridinium-4-yl) amino] phenyl] carbamoyl]-anilino]-quinolinium dibromide (NSC 113089) to lipid extracts from rat kidney, liver, heart and skeletal muscle has been studied. Such binding is saturable with an apparent KD congruent to 1.6 microM. Drug binding to the lipid extracts is displaceable by spermine, spermidine, calcium ions and protons. Spermine is the best displacing agent, achieving half drug displacement from the lipid extracts at approximately 6.3 microM regardless of tissue. The inability of the displacing agents to displace all the NSC 113089 bound to the lipid extracts as well as differences in the amount of agent bound to as compared to amount of drug displaced from the lipid extracts indicate that a number of drug binding sites may be present in the lipid extracts. The similarities of drug binding by rat tissue lipids to similar lipids extracted from normal animal and tumor tissues is discussed.

Animals↗
PubMed1977

The effect of various resuscitative regimens on hemorrhagic shock in puppies.

Since shock secondary to hemorrhage is not infrequently encountered in the pediatric patient, a puppy model was devised to help measure and monitor cardiovascular and metabolic changes that occur before and after resuscitation from hypovolemic shock (mean arterial pressure of 50 mm Hg for 1 hr). Three resuscitation protocols were compared: whole blood (replacement:shed) 1:1, 5% albumin in Ringer's lactate 1:1; and Ringer's lactate 3:1. All dogs survived the experiment and responded similarly during the shock period. Thermal dilution cardiac output rose in all groups after resuscitation; however, in the Ringer's lactate and 5% albumin groups, cardiac output was statistically greater than that observed in the blood group. In all groups, pH and blood pressure approached but did not return completely to baseline levels after resuscitation. In addition, early resuscitation demonstrated a further decrease pH ("hidden acidosis") before it began to return toward normal as resuscitation progressed. This study suggests that the infusion of large volumes of Ringer's lactate or 5% albumin in Ringer's lactate are equally efficacious in the treatment of hemorrhage. However, 5% albumin seems to be preferable because it allows infusion of a smaller quantity of electrolyte solution with equivalent physiologic benefits.

Albumins↗
PubMedDate not supplied

Hsp70, an immunological actor playing with the intracellular self under oxidative stress.

Heat shock proteins (HSPs) have originally been studied at cellular and molecular levels for their role in resistance to stress. More recently, HSPs have received the attention of immunologists for their ability to stimulate the adaptive and innate immune system. However, the immunological consequences mediated by their expression under stress have not been fully explored. Recent studies on the inducible Hsp70 have promoted the emergence of a new link between oxidative stress and immune response. This view is based on the observation that (i) the stress inducible Hsp70, but not the constitutive Hsc70 co-segregates with immunogenicity of tumour cells in vivo, (ii) the stresses that induce Hsp70 expression also give rise to cellular oxidation, and (iii) an active immune response is a source of oxidative stresses. Here, one explores the hypothesis that, under oxidative stress, Hsp70 is more efficient in discriminating intracellular 'non-self polypeptides' than Hsc70, leading to a more efficient stimulation of the immune system.

Animals↗
PubMedDate not supplied

Cell type-dependence for Vpu function.

Human immunodeficiency virus type 1 Vpu has been shown to facilitate virus release from HeLa cells. We demonstrated that Vpu expression is not required for efficient virus release from Cos 1 and CV-1 cells. A yeast GAL4 transcriptional activation system was used to screen for cellular proteins that may interact with Vpu. One such protein was identified which we provisionally designate "Vpu interactive protein" or VIP.

Animals↗
PubMedDate not supplied

Gender differences in utilization of exercise treadmill testing: a claims-based analysis.

Significant data exist to suggest that women with coronary artery disease (CAD) have worse outcomes than men. One explanation is that women present with more advanced disease because of a lack of screening and early detection. To examine this, we performed a claims-based analysis of exercise treadmill testing (ETT) within an urban managed care population. We analyzed all claims for 57,793 covered lives. Utilization rates for ETT were calculated for men and women by age group. ETT utilization between men and women demonstrated significant differences: 49.2 tests/1,000 men versus 25.0 tests/1,000 women (p < 0.001). This 2:1 ratio was observed across multiple age strata. Significant differences in ETT utilization exist between men and women, even in older populations in which the incidence of CAD in women exceeds that in men. ETT often is the initial screening test for detecting CAD; these gender differences in ETT utilization may result in underdetection of CAD in women and treatment at later stages of disease when interventions are less effective.

Adult↗
PubMedDate not supplied

My cheque and my children: the long road to empowerment in child welfare.

This article is based upon a two-year research project in a government child welfare agency in British Columbia involving frontline child welfare workers and women who are single parents. Based upon previous research with public child welfare workers, the authors developed several principles that emphasized the importance of female clients and frontline workers having the power to shape practice according to their joint plans. The article reports on the achievements of women who are single parents and of workers once they are given the freedom to redevelop services. The underlying concept--empowerment--is reviewed and a comprehensive definition of the term, based upon client and worker empowerment, is proposed.

British Columbia↗