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Biomedical subjects

C Dickinson

Publications and source records attributed to C Dickinson.

At least 37 records · Page 2Linked to original sources
PubMed1997

Biological and conformational examination of stereochemical modifications using the template melanotropin peptide, Ac-Nle-c[Asp-His-Phe-Arg-Trp-Ala-Lys]-NH2, on human melanocortin receptors.

Examination of conformationally constrained melanotropin peptide (Ac-Nle4-c[Asp5-His-Phe7-Arg-Trp9-Ala-Lys]-NH2) on four human melanotropin receptors (hMC1R, hMC3R, hMC4R, and hMC5R) resulted in identifying the importance of ligand stereochemistry at positions 5, 7, and 9 for agonist binding affinity and receptor selectivity. A trend in ligand structure-activity relationships emerged for these peptides, with the hMC1R and hMC4R possessing similar tendencies, as did the hMC3R and hMC5R. alpha-MSH (Ac-Ser-Tyr-Ser-Met4-Glu-His-Phe7-Arg-Trp-Gly-Lys-Pro-Val-NH2), NDP-MSH (Ac-Ser-Tyr-Ser-Nle4-Glu-His-D-Phe7-Arg-Trp-Gly-Lys-Pro-Val-NH2), and MTII (Ac-Nle4-c[Asp5,D-Phe7,Lys10]-alpha-MSH(4-10)-NH2) were also examined at each of these melanocortin receptors. Interestingly, the linear NDP-MSH possessed greater binding affinity for the hMC3R and hMC5R than did the cyclic analogue MTII. The peptide Ac-Nle-c[Asp-His-Phe-Arg-D-Trp9-Ala-Lys]-NH2 demonstrated the greatest differentiation in binding affinity between the hMC1R and hMC4R (78-fold). Analogue Ac-Nle-c[Asp-His-Phe7-Arg-Trp-Ala-Lys]-NH2 resulted in micromolar binding affinity (or greater) at the hMC3R and hMC5R, demonstrating the importance of D-Phe7 for ligand binding potency at these receptors. Ac-c[Asp-His-Phe-Arg-Trp-Ala-Lys]-NH2 resulted in loss of binding affinity at the hMC5R, implicating the importance of Nle4 (or a hydrophobic residue in this position) for binding to this receptor. Ac-Nle-c[D-Asp5-His-Phe-Arg-Trp-Ala-Lys]-NH2 was unable to competitively displace [125I]NDP-MSH binding at micromolar concentrations on the hMC3R and hMC5R, suggesting the importance of chirality of Asp5 either for ligand-receptor interactions or for orientation of the side chain lactam bridge and the structural integrity of the peptide conformation. Energy calculations performed for these peptides resulted in the identification of a low-energy ligand conformer family that is common to all the ligands. The differences in ligand binding affinities observed in this study are postulated to be a result of different ligand-receptor complexed interactions and not solely to the ligand structure.

Amino Acid Sequence↗
PubMed1997

Effects of recombinant agouti-signaling protein on melanocortin action.

Mouse agouti protein is a paracrine signaling molecule that has previously been demonstrated to be an antagonist of melanocortin action at several cloned rodent and human melanocortin receptors. In this study we report the effects of agouti-signaling protein (ASIP), the human homolog of mouse agouti, on the action of alpha-MSH or ACTH at the five known human melanocortin receptor subtypes (hMCR 1-5). When stably expressed in L cells (hMC1R, hMC3R, hMC4R, hMC5R) or in the adrenocortical cell line OS3 (hMC1R, hMC2R, hMC4R), purified recombinant ASIP inhibits the generation of cAMP stimulated by alpha-MSH (hMC1R, hMC3R, hMC4R, hMC5R) or by ACTH (hMC2R). However, dose-response and Schild analysis indicated that the degree of ASIP inhibition varied significantly among the receptor subtypes; ASIP is a potent inhibitor of the hMC1R, hMC2R, and hMC4R, but has relatively weak effects at the hMC3R and hMC5R. These analyses also indicated that the apparent mechanism of ASIP antagonism varied among receptor subtypes, with characteristics consistent with competitive antagonism observed only at the hMC1R, and more complex behavior observed at the other receptors. ASIP inhibition at these latter receptors, nonetheless, can be classified as surmountable (hMC3R, hMC4R and hMC5R) or nonsurmountable (hMC2R). Recombinant ASIP also inhibited binding of radiolabeled melanocortins, [125I-Nle4, D-Phe7] alpha-MSH and [125I-Phe2, Nle4]ACTH 1-24, to the hMCR 1-5 receptors, with a relative efficacy that paralleled the ability of ASIP to inhibit cAMP accumulation at the hMC1R, hMC2R, hMC3R, and hMC4R. These results provide new insight into the biochemical mechanism of ASIP action and suggest that ASIP may play an important role in modulating melanocortin signaling in humans.

Agouti Signaling Protein↗
PubMed1997

Risk status at discharge and cause of death for postneonatal infant deaths: a total population study.

OBJECTIVES: To obtain population-based, clinical information regarding potentially modifiable factors contributing to death during the postneonatal period (28 to 364 days), we examined all postneonatal infant deaths in four areas of the United States to determine: (1) the cause of death from clinical and autopsy data rather than vital statistics, (2) whether death occurred during initial hospitalization or after discharge, and (3) the portion of postneonatal mortality attributable to infants who left the hospital with identified high-risk medical conditions. DESIGN AND SETTING: Retrospective medical record review of all postneonatal infant deaths with birth weights greater than 500 g (total N = 386) born to mothers residing in: (1) the city of Boston (1984 and 1985, N = 55), (2) the city of St Louis and contiguous areas (1985 and 1986, N = 123), (3) San Diego County (1985, N = 112), and (4) the state of Maine (1984 and 1985, N = 96). Deaths were identified using linked birth and death vital statistics, and medical record audits of infants' and mothers' charts were performed. Causes of death were obtained from medical record review in conjunction with autopsy if performed (72%, N = 278), medical record alone (17%, N = 67), or vital statistics if no other source was available (11%, N = 41). The medical conditions at the time of discharge for each infant were reviewed and, if judged to confer an increased risk of morbidity or mortality, were classified as high risk. RESULTS: The causes of death were sudden infant death syndrome (47%, N = 181), congenital conditions (20%, N = 77), prematurity-related conditions (11%, N = 43), infections (9%, N = 34), external causes (including injuries, drownings, ingestions, and burns) (7%, N = 25), and other (6%, N = 23). In 24% of congenital and 25% to 44% of prematurity-related deaths, infection was the acute or associated cause of death. Infants born to black mothers were more likely than those born to white mothers to die during the postneonatal period of all major causes of death (7.3 per 1000 vs 3.0 per 1000). Overall, 18% (N = 68) of deaths occurred to infants who never left the hospital; 79% (N = 305) of the infants were discharged before death; and discharge status was unknown in 3% (N = 13). Eighty-one percent of all infants with prematurity-related postneonatal deaths were never discharged, and of the total infants who were initially discharged, only 1% (N = 4) subsequently died of prematurity-related causes. Of all postneonatal deaths, only 16% (N = 62) left the hospital with identified high-risk medical conditions. CONCLUSIONS: These findings suggest that the etiology of postneonatal mortality is heterogeneous, with significant complexity in attributing specific causes of death and making designations of "preventability." The vast majority of infants who died of prematurity-related postneonatal causes never left the hospital, and only a small percentage of all infants that left the hospital before death were identified as being at high medical risk. Therefore, strategies for further decreasing postneonatal mortality must link high-risk follow-up programs to more comprehensive strategies that address risk throughout pregnancy and early childhood.

Cause of Death↗
PubMed1996

Characterizations of the unusual dissociation properties of melanotropin peptides from the melanocortin receptor, hMC1R.

Variation in the degree of prolonged (residual) biological activity of the melanotropin peptides alpha-MSH (alpha-melanocyte-stimulating hormone, Ac-Ser-Tyr-Met-Glu- His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2) and the superpotent analogues [Nle4,DPhe7]alpha-MSH (MT-I) and Ac-[Nle4,Asp5,DPhe7,Lys10]alpha-MSH(4-10-NH2 (MT-II) has stimulated considerable interest regarding this biological phenomena. We have examined the differences in their relative dissociation rates from the melanocortin receptor, hMC1R, to try and correlate peptide dissociation rates with the observations of prolonged biological activity. Interestingly, these studies revealed that alpha-MSH remained 25% bound, MT-I 65% bound, and MT-II 86% bound 6 h after the ligand had been removed from the assay medium. The relative dissociation rate of MT-II was 4 times slower than that for alpha-MSH and 2 times slower than that for MT-I, which was 2 times slower than that for alpha-MSH. These data suggest that slow dissociation kinetics (hours) may contribute to the prolonged biological activities observed for both MT-I and MT-II peptides in vitro and in vivo. The prolonged binding, biological activities, and enzymatic stability of MT-I and MT-II make them putative candidates for clinical uses such as external scintigraphy for the localization of tumors (i.e., melanoma).

Amino Acid Sequence↗
PubMed1995

Topographical modification of melanotropin peptide analogues with beta-methyltryptophan isomers at position 9 leads to differential potencies and prolonged biological activities.

We have introduced topographical constraints at the 9 position of a superpotent cyclic alpha-melanotropin analogue, Ac-Nle4-Asp5-His6-DPhe7-Arg8-Trp9-Lys10-NH2, by incorporating a methyl group at the beta-carbon of Trp9. These studies were performed on the Trp side chain pharmacophore to identify the bioactive topography of the indole moiety with melanocortin MC1 receptors. The four beta-MeTrp9 isomers, in addition to the stereochemical controls L- and DTrp9, were used to probe differential receptor molecular recognition of the tryptophan moiety in two bioassay systems. Approximately a 460-fold difference in potency was observed between the diastereoisomeric peptides in the frog skin bioassay, with only 33- and 10-fold efficacy differences observed in binding and intracellular cAMP accumulation, respectively, on the human melanocortin receptor, hMC1R. The relative orders of potencies in the frog skin bioassay were 2R,3S > 2S,3S = 2R,3R >> 2S,3R and for the hMC1R were 2S,3S > 2R,3R > 2R,3S >> 2S,3R. Of particular interest is the ability of these topographically constrained ligands to differentially affect prolonged biological activity. The 2R,3R diastereoisomeric peptide possessed superprolonged activity, whereas the 2S,3S peptide lacked any residual activity in the frog skin bioassay. However, on the melanocortin receptor, the 2S,3S diastereoisomeric peptide maintained slow dissociation rates (t1/2 = 7 h), while the other diastereoisomeric peptides possessed dissociation t1/2 rates of ca. 2 h. These data strongly implicate ligand-receptor interactions and kinetics as contributing to the observed prolonged biological activities and clearly illustrate topographical recognition differences between these two peripheral MC1 receptors involved in skin pigmentation. This study also demonstrates that topographical modifications of pharmacophore side chain residues, in addition to identifying preferential side chain orientation, can be a useful strategy for the design of peptides to increase the duration of biological activity, relative to the native ligand.

Amino Acid Sequence↗
PubMed1995

Rating of perceived exertion and heart rate relative to ventilatory threshold in women.

Forty women took part in a study designed to investigate self-selected exercise intensity relative to ventilatory threshold during circuit weight training (CWT) and exercise-to-music (ETM) sessions. Subjects were assigned to one of two groups which were beginners (B) or habitual exercisers (HE) on the basis of their exercise habits. All subjects first underwent a laboratory cycle ergometer test involving a continuous incremental exercise protocol from which ventilatory threshold (VT) was determined using piecewise linear regression analysis. This point was expressed in terms of heart rate (VTHR) and rating of perceived exertion (VTRPE). These points were then compared with those determined during exercise training sessions (TRAHR and TRARPE respectively). The results showed that mean(s.d.) TRARPE (13.5(1.1) was not significantly different to mean(s.d.) VTRPE (12.8(0.5); P > 0.05) but that mean(s.d.) VTHR (134.8(13.5) beats min-1) and TRAHR (154.9(12.0) beats min-1) were different (P < 0.05). Beginners trained at a significantly higher percentage above VTHR than habitual exercisers (118(3.1) versus 111(2.8)% P < 0.05). During CWT the mean(s.d.) TRAHR for beginners (143.2(7.6) beats min-1) was significantly lower than that for habitual exercisers (152.5(10.1) beats min-1; P < 0.05), but not different during ETM (P < 0.05). When these TRAHR values were expressed relative to an estimated maximum heart rate (EMHR) they represented 86.5% in ETM and 80.5% in CWT which were different (P < 0.05). These results suggest that regardless of habitual exercise level and training mode, these women selected a common intensity of effort that was compatible with the described RPE.

Adolescent↗
PubMed1995

The role of the community pharmacist as a dental health adviser.

In this study 409 community pharmacists answered a questionnaire about the number and nature of their customers' inquiries regarding oral health and topics related to dentures. Three-quarters of respondents were asked, at least once a week, for advice on a wide range of such matters. The results indicate that pharmacists' knowledge is poor and it is therefore concluded that more material concerning oral health should be given in their undergraduate and postgraduate education. The general public would benefit substantially.

Education, Pharmacy↗
PubMed1994

Binding and cAMP studies of melanotropin peptides with the cloned human peripheral melanocortin receptor, hMC1R.

Binding and stimulation of cAMP by the melanotropin peptides alpha-MSH (alpha-melanocyte-stimulating hormone) and its superpotent analogues [Nle4, DPhe7]alpha-MSH (MT-I) and Ac-[Nle4,[formula: see text]alpha-MSH4-10-NH2 (MT-II) were undertaken to examine their respective properties on the human peripheral melanocyte melanocortin receptor, hMC1R. alpha-MSH was found to possess a binding IC50 value of 6.5 +/- 0.9 x 10(-9) M and cAMP EC50 value of 2.0 +/- 0.6 x 10(-9) M. MT-I possesses a binding IC50 value of 1.2 +/- 0.3 x 10(-9) M and a cAMP EC50 of 0.5 +/- 0.03 x 10(-9) M. MT-II possesses a binding IC50 of 0.57 +/- 0.08 x 10(-9) M and cAMP EC50 value of 0.20 +/- 0.05 x 10(-9) M.

Affinity Labels↗
PubMed1992

Quality assurance and reproducibility of high-resolution two-dimensional electrophoresis and silver staining in polyacrylamide gels.

Qualitative data from high-resolution two-dimensional electrophoresis (2DE) have become clinically useful in immunoglobulin clonality analysis, in resolution of ambiguities in immunofixation typing of paraproteins, and in genetic typing of serum proteins. Since 1986, the authors have been evaluating the College of American Pathologists Reference Preparation for Serum Proteins (RPSP) as a quality control material for 2DE because (1) it is prepared exclusively from pooled human sera, (2) the pool yields a reference pattern of mixed heterozygosity for genetic markers, and (3) RPSP is widely available as a lyophilized preparation that currently serves in the authors' laboratory as a qualitative quality control preparation and that may become a quantitative quality control material or external quality assessment material for 2DE. Using the ISO-DALT 2DE system and silver-staining, the peptide patterns were examined in 11 lots of RPSP and compared with fresh serum and with each other. Consistent differences in the 2DE pattern between RPSP and fresh serum included the presence of freeze-thaw peptides, the presence of degradation spots of apolipoprotein A-I, and the diminution of apolipoprotein spot intensities in RPSP. All lots of RPSP yielded clear identification of the eight serum proteins used for quality control calculations. Run-to-run coefficients of variation for a single lot of RPSP for four parameters of 2DE spot location and gradient reproducibility were comparable with band location reproducibility for the one-dimensional procedures of serum protein electrophoresis and lactate dehydrogenase isoenzyme electrophoresis. It is concluded that the reproducibility, that is, imprecision, of 2DE is the same as one-dimensional clinical electrophoresis techniques and that either RPSP or pooled fresh serum can serve as a satisfactory internal quality control material.

Blood Protein Electrophoresis↗
PubMed1988

Importance of noradrenergic mechanisms in the olfactory bulbs for the maternal behaviour of mice.

Both olfactory recognition and maternal experience are important determinants of successful maternal care. Lesions to the central noradrenergic projection to the olfactory bulbs prior to parturition results in cannibalism without producing a general anosmia or gross imparment of maternal behavior. Similar lesions made after parturition and maternal experience are completely without effect. We interpret these findings as providing further evidence for a noradrenergic influence on bulbar networks at parturition which are important for, and have long lasting consequences on, maternal recognition.

Animals↗
PubMed1981

Intrauterine growth: correlations of maternal nutritional status and rate of gestational weight gain.

The influence of increasing pregravid weight and gestational rate of gain on birthweight, length, head circumference and complications was investigated. Each gravida was categorized by height and pregravid weight as underweight, normal, or obese. Birthweights, lengths, and head circumferences were evaluated as well as maternal and infant complications. Within each pregravid category and each rate gain group there was an increase in mean birthweight, length, and head circumference with advancing gain and pregravid weight. The incidence of small for gestational age (SGA) infants decreased and large for gestational age (LGA) infants increased with higher gain and pregravid weight. The incidence of antepartum anemia decreased with higher pregravid weight and gain (P less than 0.02). Higher pregravid weight and rate of gestational gain may help insure optimal intrauterine growth.

Birth Weight↗
PubMed1979

Patient scheduling studied, refined.

Two hospitals used different approaches to devise equally efficient systems for scheduling and processing inpatients and outpatients for radiology procedures.

Appointments and Schedules↗