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Biomedical subjects

D A Price

Publications and source records attributed to D A Price.

At least 91 records · Page 5Linked to original sources
PubMed1998

Synaptic density in the inner molecular layer of the hippocampal dentate gyrus in Alzheimer disease.

We examined the inner molecular layer (IML) of the hippocampal dentate gyrus for possible changes in synaptic density. Material was obtained from 9 individuals with Alzheimer disease (AD) and compared to samples obtained from 10 age-matched, postmortem-matched neurologically normal controls, employing standard ultrastructural techniques. Statistical analyses demonstrated a significant decline in synaptic numbers between controls and AD subjects. This decline was accompanied by a significant increase in apposition length and resulted in a significant correlation with the synaptic density. As the number of synapses declined, the apposition length increased. Assessment was also made of the granule cells density and the analyses showed a significant decline in the synapse to granule cell ratio in the AD group. This decline in the density of synaptic contacts in the IML reflects a more widespread decline in plasticity in AD and may be related to the memory problems associated with the disease.

Aged↗
PubMed1998

Linear growth in prepubertal children with atopic dermatitis.

OBJECTIVE: To define the evolution of prepubertal growth in atopic dermatitis and the factors influencing that growth pattern. METHODS: Height and height velocity over two years, weight, triceps and subscapular skin fold thickness, and bone age were assessed in 80 prepubertal patients with atopic dermatitis and a control group of 71 healthy prepubertal school children. RESULTS: Height standard deviation scores (SDS) and height velocity SDS did not differ between patients and controls, and were not influenced by body surface area affected by atopic dermatitis, topical glucocorticoid potency, or coexisting asthma. However, height SDS (r = -0.37) and height velocity SDS (r = -0.31) correlated inversely to age in patients but not in controls. A greater proportion (z = 2.84) of patients than controls had year 2 height velocity SDS less than -1.96. Patients had a mean delay in bone age of 0.22 years and 0.41 years at the beginning of year 1 and year 2 of the study, respectively. The delay in bone age correlated positively with age (r = 0.39) and duration of atopic dermatitis (r = 0.39), and negatively with height SDS (r = -0.51) and height velocity SDS (r = -0.38). CONCLUSIONS: Prepubertal children with atopic dermatitis are not short compared with controls. However, as they approach the teenage years their height velocity decreases, the proportion of children with extremely low height velocity increases, and the delay in bone age increases. These features are consistent with the pattern of growth seen in people with constitutional growth delay.

Administration, Topical↗
PubMed1998

Efficacy and safety of growth hormone treatment in children with prior craniopharyngioma: an analysis of the Pharmacia and Upjohn International Growth Database (KIGS) from 1988 to 1996.

We studied short- and long-term responses to growth hormone (GH) treatment and adverse medical events (AE) in 488 patients with craniopharyngioma who were entered into the Kabi International Growth Study (KIGS). First-year growth response and responsiveness (n = 394) were similar to those seen in children with idiopathic GH deficiency. The growth response over 5 years (n = 152) was unaffected by the recurrence of tumour and prior tumour management, but was greater in those receiving thyroxine. Mean height standard deviation scores (SDS) at the end of GH treatment (n = 129) was -0.7+/-1.2, and 79% achieved a height over -2 SD of target height, with evidence of further growth potential. Final height SDS correlated positively with height SDS at the start of treatment and with target height SDS, whereas gain in height SDS was inversely correlated with height SDS and bone age at the start of GH treatment. The rate of recurrence of tumour, 0.045/treatment year, was greater in those who had been treated with surgery alone compared to surgery and cranial irradiation. Other AE included headaches, fluid retention and convulsions occurring at rates of 0.025, 0.005 and 0.004/treatment year, respectively. We concluded that GH treatment is safe and effective in children with craniopharyngioma and provide data for counselling of parents about outcome during GH treatment.

Body Height↗
PubMed1998

Serum insulin-like growth factor-I, IGF binding protein-3 and IGFBP-3 protease activity after cranial irradiation.

The relationship between peak growth hormone (GH), insulin-like growth factor I (IGF-I), IGF-I binding protein 3 (IGFBP-3) and IGFBP-3 protease activity was studied in 28 children and adolescents undergoing investigation of pituitary function 0.4-14.2 years after cranial or craniospinal irradiation for the treatment of CNS tumours distant from the hypothalamic-pituitary axis (n = 16) or prophylaxis against CNS leukaemia (n = 12). Seven out of 15 patients with GH deficiency (GHD) (defined as a peak GH concentration <7.5 ng/ml in a stimulation test) had IGF-I <-2 standard deviation score (SDS). None of the 28 patients had serum IGFBP-3 concentrations measured by radioimmunoassay (RIA) <-1.5 SDS with no difference between those with and without GHD. IGFBP-3 concentrations measured by RIA were strongly correlated to IGFBP-3 band density on Western ligand blot (WLB) (r = 0.71; p < 0.0001). IGFBP-3 protease activity was negatively correlated to IGFBP-3 by RIA (r = -0.55; p < 0.01) and to IGFBP-3 by WLB (r = -0.51; p < 0.01). Twenty-two patients had normal IGFBP-3 protease activity (<30% of the activity in pregnancy serum) indicating that serum IGFBP-3 protease activity does not account for the normal levels of IGFBP-3 in RIA. Low serum IGF-I but normal IGFBP-3 concentrations and in the majority normal IGFBP-3 protease activity was found in patients in the years after CNS irradiation. Neither serum IGF-I nor IGFBP-3 can be used as a reliable index of the development of radiation-induced GHD.

Adolescent↗
PubMed1998

Pathways for angiotensin II generation in intact human tissue: evidence from comparative pharmacological interruption of the renin system.

Multiple lines of evidence have suggested that alternative pathways to the angiotensin-converting enzyme (ACE) exists for angiotensin II (Ang II) generation in the heart, large arteries, and the kidney. In vitro studies in intact tissues, homogenates, or membrane isolates from the heart and large arteries have repeatedly demonstrated such pathways, but the issue remains unresolved because the approaches used have not made it possible to extrapolate from the in vitro to the in vivo situation. For our in vivo model, we studied young and healthy human volunteers, for the most part white and male; when these subjects achieved balance on a low salt diet to activate the renin system, the response of renal perfusion to pharmacological interruption of the renin system was studied. With this approach, we studied the renal vasodilator response to 3 ACE inhibitors, 2 renin inhibitors, and 2 Ang II antagonists at the top of their respective dose-response relationships. When these studies were initiated, our premise was that a kinin-dependent mechanism contributed to the renal hemodynamic response to ACE inhibition; therefore, the renal vasodilator response to ACE inhibition would exceed the alternatives. To our surprise, both renin inhibitors and both Ang II antagonists that were studied induced a renal vasodilator response of 140 to 150 mL/min/1.73 m2, approximately 50% larger than the maximal renal hemodynamic response to ACE inhibition, which was 90 to 100 mL/min/1.73 m2. In light of the data from in vitro systems, our findings indicate that in the intact human kidney, virtually all Ang II generation is renin-dependent but at least 40% of Ang I is converted to Ang II by pathways other than ACE, presumably a chymase, although other enzyme pathways exist. Preliminary data indicate that the non-ACE pathway may be substantially larger in disease states such as diabetes mellitus. One implication of the studies is that at the tissue level, Ang II antagonists have much greater potential for blocking the renin-angiotensin system than does ACE inhibition-with implications for therapeutics.

Angiotensin II↗
PubMed1998

The relationship between stature, growth, and short-term changes in height and weight in normal prepubertal children.

Human growth is a nonlinear process with marked variation in growth rate during the short-term. It is not known how long-term height gain or stature is influenced by short-term changes in height and weight. This study has addressed these issues by using thrice weekly height and weight measurements during 1 year in 43 normal prepubertal children (aged 5.7-7.7 y) to construct individual height and weight velocity curves by regression analysis. The former were comprised of 3 to 6 growth spurts separated by stasis, whereas the latter were characterized by 2 to 5 periods of weight gain separated by periods of weight loss. Stepwise regression analysis to determine characteristics of these curves that influence stature and growth showed that height SD score was correlated to the mean absolute weight velocity amplitude (+), the mean length of height velocity peaks (-), and the number of periods of weight gain (-) (r2 = 38%). In contrast, change in height SD score (delta height SD score) was correlated to the number (+) and mean amplitude (+) of the periods of weight gain and the mean height velocity peak amplitude (+) (r2 = 44%). Examination of changes in height relative to weight during the year in the whole group revealed that height increased relative to weight in autumn and spring, whereas the reverse occurred during the winter months. We conclude that 1) both height and weight velocities during 1 year show a biphasic pattern, 2) there is seasonal variation in the short-term change in height relative to weight, and 3) prepubertal stature and the amount grown through the year are related to short-term changes in height and weight. Our data indicate that large but infrequent changes in weight with growth spurts of short duration are found in tall children. Good growth during the year was related to large but frequent gains in weight and large individual spurts in height.

Body Height↗
PubMed1997

Patterns of immunodominance in HIV-1-specific cytotoxic T lymphocyte responses in two human histocompatibility leukocyte antigens (HLA)-identical siblings with HLA-A*0201 are influenced by epitope mutation.

Primary human immunodeficiency virus (HIV) infection is controlled principally by HIV-specific cytotoxic T lymphocytes (CTL) to a steady-state level of virus load, which strongly influences the ultimate rate of progression to disease. Epitope selection by CTL may be an important determinant of the degree of immune control over the virus. This report describes the CTL responses of two HLA-identical hemophiliac brothers who were exposed to identical batches of Factor VIII and became seropositive within 10 wk of one another. Both have HLA-A*0201. The CTL responses of the two siblings were very dissimilar, one donor making strong responses to two epitopes within p17 Gag (HLA-A*0201-restricted SLYNTVATL and HLA-A3-restricted RLRPGGKKK). The sibling responded to neither epitope, but made strong responses to two epitopes presented by HLA-B7. This was not the result of differences in presentation of the epitopes. However, mutations in both immunodominant epitopes of the p17 Gag responder were seen in proviral sequences of the nonresponder. We then documented the CTL responses to two HLA-A*0201-restricted epitopes, in Gag (SLYNTVATL) and Pol (ILKEPVHGV) in 22 other HIV-infected donors with HLA-A*0201. The majority (71%) generated responses to the Gag epitope. In the 29% of donors failing to respond to the Gag epitope in standard assays, there was evidence of low frequency memory CTL responses using peptide stimulation of PBMC, and most of these donors also showed mutations in or around the Gag epitope. We concluded that HLA class I genotype determines epitope selection initially but that mutation in immunodominant epitopes can profoundly alter the pattern of CTL response.

Amino Acid Sequence↗
PubMed1997

Positive selection of HIV-1 cytotoxic T lymphocyte escape variants during primary infection.

Cytotoxic T lymphocytes (CTLs) are thought to play a crucial role in the termination of the acute primary HIV-1 syndrome, but clear evidence for this presumption has been lacking. Here we demonstrate positive selection of HIV-1 proviral sequences encoding variants within a CTL epitope in Nef, a gene product critical for viral pathogenicity, during and after seroconversion. These positively selected HIV-1 variants carried epitope sequence changes that either diminished or escaped CTL recognition. Other proviruses had mutations that abolished the Nef epitope altogether. These results provide clear evidence that CTLs exert selection pressure on the viral population in acute HIV-1 infection.

Adult↗
PubMed1997

Combined structural and immunological refinement of HIV-1 HLA-B8-restricted cytotoxic T lymphocyte epitopes.

This study demonstrates that use of structural information improves the definition and optimization of cytotoxic T lymphocyte (CTL) epitopes. Epitope optimization usually requires numerous truncated peptides or a reverse immunogenetic approach, where the peptide binding motif is used to predict epitopes. These binding motifs do not reliably predict all peptides which are CTL epitopes. Comparison of 24 peptides eluted from HLA-B8 with 10 HLA-B8-restricted defined CTL epitopes demonstrated that known epitopes varied considerably at anchor positions. We used structural information based on determination of the crystal structure of the HLA-B8-GGKKKYKL complex to reassess previously described CTL epitopes, to predict new epitopes, and to predict the consequences of naturally occurring variation within epitopes. These predictions were confirmed by cytotoxicity and binding assays. Use of combined structural and immunological data more accurately defines the true peptide-binding motif of a restriction element than eluted peptide data allows.

Antigenic Variation↗
PubMed1997

Antagonism of cytotoxic T lymphocyte-mediated lysis by natural HIV-1 altered peptide ligands requires simultaneous presentation of agonist and antagonist peptides.

Mutations in human immunodeficiency virus (HIV) cluster in cytotoxic T lymphocyte (CTL) epitopes (Phillips, R. E. et al., Nature 1991. 354: 453) and are subject to immune-mediated positive selection (Price, D. A. et al., Proc. Natl. Acad. Sci. USA 1997. 94: 1890). We studied the effects of naturally occurring mutations in the HIV-1 p17 Gag HLA A2 restricted epitope SLYNTVATL on recognition by anti-HIV CTL. Most of these naturally occurring mutants escaped killing by one CTL line and the majority acted as CTL antagonists. We also investigated whether CTL exposed to a strict antagonist peptide restricted by HLA A2 were unresponsive when exposed to targets presenting the wild-type sequence. The results show that antagonism of anti-HIV CTL killing requires the simultaneous presence of agonist and antagonist peptide. We found no evidence that CTL exposed to an antagonist received a functionally negative signal since these CTL retained an unimpaired capacity to lyse targets bearing wild-type peptide.

Antigen-Presenting Cells↗
PubMed1997

Effects of cardioactive peptides on myocardial cAMP levels in the snail Helix aspersa.

Several cardioactive peptides from the pulmonate snail Helix aspersa were tested for their effects on myocardial cAMP levels, but only the family of small cardioactive peptides (SCPs) were clearly effective. SCP increased cAMP in a dose dependent manner; the time course was phasic. The structure-activity relations of this effect were examined with a set of 3 synthetic analogs having characteristics, at the carboxyterminal, of both the SCPs and FMRFamide-related peptides. The adenylate cyclase activator forskolin mimicked the mechanical effect of SCPs on the heartbeat. We conclude that the effect of SCPs on the Helix heart may be mediated by cAMP.

Animals↗
PubMed1997

Characterization of myomodulin-related peptides from the pulmonate snail Helix aspersa.

Three myomodulin-related peptides--pQLSMLRLamide, PMSMLRLamide, and SLGMLRLamide--have been purified and sequenced from extracts of whole snails. The level of immunoreactive myomodulin was shown by HPLC and RIA to be widely distributed among 26 different snail tissues, with the highest levels (higher even than those in the central ganglia) occurring in certain male reproductive organs. Synthetic pQLSMLRLamide modified either the spontaneous rhythmic activity or the resting tone of several isolated muscular organs: the aorta, ventricle, upper gut, epiphallus, flagellum, and spermatheca; but the retractor muscles of the pharynx, penis, and tentacle were unaffected.

Animals↗
PubMed1997

African-Americans on maintenance dialysis: a review of racial differences in incidence, treatment, and survival.

African-Americans are the fasting growing racial minority with end stage renal disease (ESRD) in the United States. Currently, African-Americans comprise approximately 31% of the ESRD population. African-Americans are almost a decade younger than their white (referring to non-Hispanic white) counterparts with ESRD with a mean age of 58 years old. Although African-Americans systematically receive less dialysis than whites (Kt/V of 1.05 versus 1.18, respectively), their survival is higher. The 2-year survival probability of African-Americans is 66.2% in comparison with 59.8% for whites. This improved survival with ESRD is accompanied by an improved quality of life for African-Americans. Their enhanced quality of life is reflected by a greatly decreased frequency of withdrawing from dialysis treatments. In this article, we will examine the reasons why African-Americans have an excessive incidence of selective diseases that culminate in ESRD. We will explore the factors that influence the difference in dialysis modality selection between African-Americans and whites. Lastly, we will pose and judge several hypotheses that may account for the improved survival enjoyed by African-Americans with ESRD. We contend that research to clarify the basis for these differences between African-Americans and whites with ESRD will improve outcomes for both populations and is fiscally sound health policy.

Black or African American↗
PubMed1997

Autonomy of the renin system in type II diabetes mellitus: dietary sodium and renal hemodynamic responses to ACE inhibition.

Recognition that non-insulin-dependent diabetes mellitus (NIDDM) is a leading cause of end-stage renal disease (ESRD), and a focus of recent therapeutic and genetic studies on the renin system have rekindled interest in mechanisms by which angiotensin converting enzyme (ACE) inhibitors influence the diabetic kidney. We evaluated the renal hemodynamic status of 19 hypertensive patients with NIDDM under controlled sodium balance, low (10 mmol/day for 5 to 7 days) or high (200 mmol/day for 5 to 7 days). The renal plasma flow (RPF) response to ACE inhibition and to angiotensin II (Ang II) infusion was measured as para-aminohippurate (PAH) clearance before and during enalapril administration (10 mg b.i.d. for 3 days). Our premise was that if renal vasodilation induced by ACEI involves kinins, prostaglandins, and/or nitric oxide, vasoconstrictor responses to Ang II would be blunted. Conversely, if the dominant ACE inhibitor action were a reduction in Ang II formation, the consequence would be up-regulation and an enhanced vasoconstrictor response to exogenous Ang II. RPF in NIDDM on a high-salt diet was lower than in age-matched controls (477 +/- 25 vs. 551 +/- 25 ml/min/1.73 m2; P = 0.02). Enalapril increased RPF in NIDDM to 511 +/- 29 ml/min/1.73 m2 (P < 0.05) and enhanced renal vasoconstrictor responses to Ang II infusion, from -68 +/- 9 to -106 +/- 18 ml/min/1.73 m2 (P = 0.03). Baseline plasma renin activity (PRA) and plasma aldosterone significantly exceeded matched normotensive controls (1.1 +/- 0.5 vs. 0.3 +/- 0.1 ng AI/ml/hr and 10 +/- 0.9 vs. 4.1 +/- 0.5 ng/dl, P < 0.01, respectively). Conversely all measures in studies on a low-salt diet were normal. Our findings indicate that: (1) NIDDM with hypertension is associated with reduced RPF when dietary salt intake is high, (2) reduced Ang II formation is the dominant mechanism of ACEI-induced renal vasodilation in hypertensives with NIDDM; and (3) the sustained renal hemodynamic responses to ACE inhibition despite high-salt balance, and the increased PRA suggest an autonomous renin-angiotensin system suppressed subnormally by a high salt diet in patients with NIDDM despite greater volume expansion.

Adult↗
PubMed1997

Urinary IGF and IGF binding protein-3 in children with disordered growth. The North West Paediatric Endocrine Group.

OBJECTIVE: Both IGF-I and IGFBP-3 reflect spontaneous GH secretion in healthy individuals. We have evaluated the clinical usefulness of urinary IGF-I and IGFBP-3 measurements in the diagnosis of children with disordered growth. DESIGN: Serum IGF-I and IGFBP-3 radioimmunoassays (RIA) were developed, and modified for quantitation in urine. The relationship between serum and urine levels, and the performance of these tests in the diagnosis of GH deficiency (GHD) were examined. PATIENTS: Sixty-nine children (age 9.5 +/- 3.6 years; 37 boys, 32 girls) provided a timed overnight urine collection and a serum sample collected on the same morning. Subjects were defined as GHD (n = 22) or short normal (SN; n = 47) on the basis of medical history, clinical examination, auxology and peak response to a GH stimulation test (< 20 mU/L in GHD patients). MEASUREMENTS: IGF-I and IGFBP-3 in serum and urine were measured by RIA, urinary GH (uGH) by immunoradiometric assay (IRMA) after dialysis and urinary creatinine by the alkaline picrate method. Urine results were expressed as total amount excreted (tulGFBP-3 (microgram), tulGF-1 (ng), tuGH (ng), tuCrt (mmol). RESULTS: Urine IGF-I and IGFBP-3 excretion correlated significantly to serum levels of IGF-I and IGFBP-3 and also to tuGH excretion. There was a strong positive relationship between both urinary peptides and tuCrt, which suggested that renal filtration was the source of these peptides in urine. In addition, there were significant correlations with age, bone age and height SD score, of similar magnitude to those for tuGH. In prepubertal children, serum IGF-I and IGFBP-3 were significantly lower in GHD compared with SN children, while in puberty only serum IGFBP-3 was significantly lower in GHD. There was no difference however, in tulGF-I or tulGFBP-3 between GHD and SN children either prepubertally or in puberty with near complete overlap of the values between groups. CONCLUSIONS: Measurements of tulGF-I and tulGFBP-3 have no place in the diagnosis of childhood GHD. Nonetheless, the significant correlations between serum and urinary IGF-I and IGFBP-3 levels and their correlation to uGH indicate that these peptides could be used as non-invasive physiological markers of the GH-IGF axis.

Adolescent↗