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PubMed1992

[Serum human growth hormone assay. Comparison of six assay kits].

Measurements of human growth hormone (hGH) plasma levels using mono or polyclonal antibodies based on kits are often highly variable depending upon the kit used. We compared six kits commercially available: one based on polyclonal antiserum, five based on monoclonal antisera. We measured 695 sera obtained in short stature children (GH deficiency or normal GH secretory) and adults (normal, hypopituitarism or acromegaly). Our results confirm the variability between the assays. The maximal variation was obtained with SBhGH kit which showed mean results 1.7 fold higher than those obtained with hGH Coatria. Using the OMS 80.205 standard with the six kits, we found a good correlation between the six kits indicating that the standard used in each case was not responsible for the observed variations. This suggest that the different antibodies used in these kits may recognize different isoforms of circulating hGH. In addition variations in reagents used in the different kits may also explain these discrepancies. The variations observed using these six commercially available kits may have important clinical repercussion and especially may impede the diagnosis in hGH deficiency in children.

Adolescent↗
PubMed1982

Correlates of dental anxiety in a university population.

The purpose of this study was to identify correlates of dental anxiety in university students. Dental anxiety was measured by means of the Corah Dental Anxiety Scale. Information about the students' dental attitudes, perceptions, and past dental experiences was collected by a written questionnaire administered to an approximately 13 percent random sample of all full-time students. The response rate was 27.3 percent (n = 846). The mean dental anxiety score for the entire study group was 8.77; mean scores for men (8.44) and women (9.10) were significantly different. Of the 18 independent variables studied, seven were found to be significantly associated with dental anxiety scores: sex, frequency of childhood visits to the dentist, childhood experience with dentists, frequency of mothers' visits to a dentist, perceived number of types of services required, symptoms as reason for last dental visit, and number of preventive actions taken prior day. As a group, the independent variables explained 22.8 percent of the observed variation in dental anxiety scores. When the amount of variation which was explained by each of the independent variables was considered separately four variables were found to be significant: childhood experience with dentists, gender, attitudes toward dentists, and number of preventive actions taken the prior day. Further studies are required to identify additional antecedents of dental anxiety in university students. These studies should focus on the ability of the antecedents to explain observed variation in anxiety levels.

Adult↗
PubMed1981

A genetic analysis of taste threshold for phenylthiocarbamide.

Taste threshold for phenylthiocarbamide (PTC) was measured in 393 offspring from the families of 85 monozygotic (MZ) twin pairs. PTC scores were bimodally distributed with modes at one and eight and the antimode at five. Because of the non-normality of the distribution, a jackknife procedure was used to obtain 95% confidence intervals for the estimates of genetic, maternal, and environmental parameters. Analyses which assumed no epistasis and which included additive genetic effects revealed that 37.9% of the observed variation in PTC threshold was due to additive genetic effects, 16.6% was due to dominance effects, 14.2% was due to maternal effects, 13.7% was due to a common sibship environment, and 17.6% was due to random environmental effects, yielding a broad sense heritability of 0.55 for the threshold ability to taste PTC. Analyses which did not include additive genetic effects revealed 26.6% of the observed variance was due to dominance effects, 23.6% to maternal effects, and 49.8% to environmental effects at the 0.67 confidence levels, but that environmental factors accounted for 72.4% and dominance effects for 23.6% of the observed variation at the 95% level.

Adolescent↗
PubMed1985

Identifying severe aortic valvular stenosis by bedside examination.

Sixty-seven consecutive symptomatic patients with aortic valvular stenosis (AS) and no or slight aortic incompetence were prospectively examined bedside by a senior cardiologist before an invasive pre-operative investigation. A history of effort syncope had the highest predictive value (pos), 100%, for a significant degree of AS (defined as a calculated valve area less than or equal to 0.9 cm2 or a peak systolic pressure difference across the valve of greater than or equal to 40 mmHg). The absence of effort syncope had a predictive value (neg) of 40%. The corresponding figures for peak intensity of the murmur in mid-systole were 93 and 82%, respectively. For the combination of effort syncope and/or mid-systolic peak intensity of the murmur (borderline findings included) the predictive values were 90% (pos) and 94% (neg), respectively. No other combination of symptoms and physical finding was more discriminating. This combination of criteria for prediction of a significant stenosis was prospectively applied to the next 39 AS patients. The criteria were fulfilled by 29 patients and all were found to have a significant AS as were four of the 10 patients not fulfilling the criteria. These four falsely negative patients had a valve area/peak pressure difference of 0.5, 0.8, 0.8 cm2 and 43 mmHg. The inter-observer variation was studied in a third series by two senior cardiologists independently examining 22 AS patients. They were concordant in all with regard to a history of effort syncope and in all but one (0.6 cm2) with regard to the timing of the peak murmur. Bedside examination of an AS patient by an experienced cardiologist has a good predictivity for severity, and the inter-observer variation is low. Non-invasive laboratory investigations have only a supplementary role. However, as many patients have effort angina, a pre-operative invasive procedure including coronary arteriography is often unavoidable.

Adult↗
PubMed1992

Circadian variation in ischemic threshold. A mechanism underlying the circadian variation in ischemic events.

BACKGROUND: There is a circadian pattern in the occurrence of cardiac events in patients with coronary artery disease. Whether changes in coronary vascular tone contribute to these phenomena is unknown. We measured the ischemic threshold, defined as either the heart rate or rate-pressure product at 1-mm ST segment depression during treadmill exercise and used it as an index of the lowest coronary vascular resistance; the premise was that when ischemic threshold became lower, coronary vascular resistance was higher, and vice versa. METHODS AND RESULTS: Fifteen patients (group A) with stable coronary artery disease underwent four identical treadmill exercise tests in 24 hours, and ischemic threshold was measured as the heart rate at the onset of 1-mm ST depression. Before each treadmill test, postischemic forearm vascular resistance was measured after 5 minutes of forearm occlusion, using strain-gauge plethysmography. Sixteen additional patients (group B) underwent two treadmill tests at 8 AM and 1 PM, and ischemic threshold was measured as the heart rate-blood pressure product at 1-mm ST depression. A circadian variation was noted: In group A, the heart rate-derived ischemic threshold was lower at 8 AM and 9 PM compared with noon and 5 PM (p less than 0.03). Also, in group B, the rate-pressure product-derived ischemic threshold was 8 +/- 2% lower at 8 AM compared with 1 PM (p = 0.008). A circadian variation parallel to the observed variation in ischemic threshold was also noted in the postischemic forearm blood flow, which was lower in the morning and at night (p less than 0.004). There was a strong correlation between postischemic forearm blood flow and ischemic threshold (p less than 0.0001), such that ischemic threshold was lower at the time of day when postischemic forearm blood flow was lower, and vice versa. CONCLUSIONS: A lower ischemic threshold in the morning suggests that the ischemia-induced coronary vascular resistance is increased at this time, a finding supported by a similar variation in postischemic forearm vascular resistance. Parallel changes in forearm and coronary resistance suggest that generalized (neural or humoral factors) rather than local factors are responsible for the observed circadian changes. Increased coronary tone in the mornings may not only contribute to the higher incidence of transient ischemia but may help trigger acute cardiac events at this time.

Aged↗
PubMed1986

Follicular center cell lymphoma. Morphologic data relating to observer reproducibility.

Subjectivity and observer variation in non-Hodgkin's lymphoma continues to plague current classification schemes. It was thought important to assess objectively derived morphometric data to see if three categories of follicular center cell (FCC) lymphomas, follicular small cleaved cell, follicular mixed small cleaved and large cell, and diffuse and nodular large cell, actually fall into distinctly separate classes based on nuclear parameters. Mean nuclear area, contour index and invagination depth of neoplastic lymphocytes, and the percentage of invaginated and clefted nuclear profiles in each example of FCC lymphoma were evaluated by three different approaches. Results obtained from distribution of the morphometric data in scatter diagrams, calculation of the overlap index, and linear regression values, all revealed considerable (but variable) degrees of overlap between the three FCC subtypes regardless of the nuclear parameter employed. Where separation between FCC lymphomas was maximal, although still incomplete, there was no consistent correlation between the nuclear parameter and the pair of FCC lymphomas being compared. At least in terms of nuclear morphological features, non-Hodgkin's lymphomas of FCC type seem to represent a continuum of one disease process. The information provides a basis for understanding some reasons underlying the problem of observer variation in non-Hodgkin's lymphoma.

Cell Nucleus↗
PubMed1990

Histological grading of prostatic carcinoma in prostatectomy specimens. Comparison of prognostic accuracy of five grading systems.

The prognostic accuracy of 5 histological grading systems (Broders, Anderson, Mostofi, Gleason and Mostofi-Schroeder) was compared. Grading was performed on 50 prostatectomy specimens by 5 pathologists. The results were averaged so as to reduce the impact of inter-observer variation. The Cox proportional hazards model was used to estimate the relationship between average grading scores and both time-to-recurrence and time-to-death by prostatic carcinoma. Age at surgery was considered to be a possible confounding factor and adjusted accordingly. The prognostic impact of the 5 grading systems (related to both recurrence and death caused by prostatic carcinoma) was judged by the likelihood ratio (LR) test score (chi 2 distributed with 1 df); for time-to-recurrence for the Mostofi-Schroeder score the LR was 6.54 and for the Gleason system it was 1.79. A stepwise procedure demonstrated that the best prognostic performance was reached with the Mostofi-Schroeder and Broders systems used together (with Mostofi-Schroeder weighted 1.5 times larger than Broders). For time-to-recurrence the median grading result was also used, giving results similar to the mean grading result. For time-to-death from prostatic carcinoma the LR test scores for all grading systems were relatively low. In this analysis the outcome of the Gleason system showed a minimum of prognostic ability, whereas the Broders and Mostofi-Schroeder systems had a reasonable predictive ability. Since the inter-observer variation of the Mostofi-Schroeder system was large, the Broders system is preferable. The restrictions and implications of this study are discussed and a brief review of the prognostic importance of grading of prostatic carcinoma is presented.

Aged↗
PubMed1990

A procaryotic regulatory factor with a histone H1-like carboxy-terminal domain: clonal variation of repeats within algP, a gene involved in regulation of mucoidy in Pseudomonas aeruginosa.

A novel procaryotic transcriptional regulatory element, AlgP, with a histone H1-like carboxy-terminal domain was identified in Pseudomonas aeruginosa. AlgP is required for transcription of the key biosynthetic gene algD, which is necessary for production of the exopolysaccharide alginate causing mucoidy in P. aeruginosa. Mucoidy is a critical virulence determinant of P. aeruginosa invariably associated with the respiratory infections causing high mortality in cystic fibrosis. Here we show that AlgP and histones H1 both have repeated units of the Lys-Pro-Ala-Ala motif (KPAA) and its variations within their long (over 100 amino acids) carboxy-terminal domains. This region of histone H1 tails has been shown to bind to the linker DNA in eucaryotic chromatin fibers. A synthetic 50-mer peptide consisting of repeats from the AlgP carboxy-terminal domain was found to bind DNA in a mobility shift DNA-binding assay. AlgP is encoded by a gene that contains multiple direct repeats organized as tandem, head-to-tail, 12-base-pair (bp) units overlapping with six highly conserved 75-bp units. The repetitive structure of the algP gene appears to participate in the processes underlying the metastable character of mucoidy in P. aeruginosa. Relatively large DNA rearrangements spanning the region with tandem direct repeats encoding the carboxy-terminal histone H1-like structure of AlgP were detected in several strains upon conversion from the mucoid to the nonmucoid phenotype. The frequency of the detectable algP rearrangements associated with the transition into the nonmucoid state varied from strain to strain and ranged from 0 to 50%. The nonmucoid derivatives with the clearly rearranged chromosomal copy of algP were complemented to mucoidy with plasmids containing algP from P. aeruginosa PAO. When a random collection of mucoid strains, isolated from different cystic fibrosis patients, was analyzed by using polymerase chain reaction, an additional level of strain-dependent sequence variation in algP was observed. Variations in the number of the 12-bp repeats were found; however, they did not appear to influence the mucoid status of the strains examined. Thus, the repeated region of algP appears to be a hot spot for DNA rearrangements and strain-dependent variability.

Amino Acid Sequence↗
PubMed2024

Comparative analysis of chloroplast genomes in ten holly (Ilex) species: insights into phylogenetics and genome evolution.

In order to clarify the chloroplast genomes and structural features of ten Ilex species and provide insights into the phylogeny and genome evolution of the genus Ilex, we conducted a comparative analysis of chloroplast genomes using bioinformatics methods. The chloroplast genomes of ten Ilex species were obtained, and their structural features and variations were compared. The results indicated that all chloroplast genomes in the genus Ilex exhibit a double-stranded circular structure, with sizes ranging from 157,356 to 158,018 bp, showing minimal differences in size. The chloroplast genomes of the ten Ilex species have a relatively conservative gene count, with a total of 134 to 135 genes, including 88 or 89 protein-coding genes, and a conserved number of 8 rRNA genes. Each chloroplast genome contains 3 to 123 SSR (Simple Sequence Repeat) sites, predominantly composed of mononucleotide and trinucleotide repeats, with no detection of pentanucleotide or hexanucleotide repeats. The variation in dispersed repeat sequences among Ilex species is minimal, with a total repeat sequence number ranging from 1 to 14, concentrated in the length range of 30 to 42 base pairs. The expansion and contraction of chloroplast genome boundaries among Ilex species are relatively stable, with only minor variations observed in individual species. Variations in non-coding regions are more pronounced than those in coding regions, with the variability in the Large Single Copy region (LSC) being the highest, while the variability in the Inverted Repeat region A (IRa) is the lowest. The divergence time among Ilex species was estimated using the MCMC-tree module, revealing the evolutionary relationships among these species, their common ancestors, and their differentiation throughout the evolutionary process. The research findings provide a valuable reference for the systematic study and molecular marker development of Ilex plants.

Genome, Chloroplast↗
PubMed1983

Variability of arterial blood gas values in stable patients in the ICU.

To establish guidelines for the interpretation of changes in arterial blood gas (ABG) values, we studied 29 clinically stable ICU patients for spontaneous variability in PaO2, PaCO2 and pH. ABGs were sampled six times over a 50-minute period, during which all patients received a fixed FIO2 of 0.5 via endotracheal tube and underwent no therapeutic interventions. Each sample was analyzed in duplicate with careful attention to method of collection and measurement. The range separating the lowest and highest PaO2 varied from 1 to 45 mm Hg (16.2 +/- 10.9 mm Hg [mean +/- SD] ). For PaCO2 this range was from 1 to 8 mm Hg (3.0 +/- 1.9 mm Hg). Coefficient of variation for PaO2 and PaCO2 averaged 5.1 +/- 3.2 percent (mean +/- SD) and 3.0 +/- 1.5 percent respectively. pH varied within 0.03 +/- 0.02 units. Percentage change in PaO2 between sequential intrapatient samples averaged 5.3 +/- 2.8 percent (mean +/- SD) and 7.1 +/- 7.9 percent over ten- and 50-minute intervals, respectively. Various clinical features were analyzed by multiple regression analysis for their relation to PaO2 variation. Only leukocyte count and mean arterial oxygen content were statistically significant associations (p less than 0.05), but together explained less than 35 percent of the variation observed. Because considerable spontaneous variation occurs, even in stable patients, clinicians should base therapeutic decisions on trends in PaO2 values rather than on isolated changes interpreted without appropriate clinical correlation.

Adult↗
PubMed1991

Using replicate observations in observer agreement studies with binary assessments.

By introducing replicate observations into observer agreement studies, one can obtain better measures of observer agreement than heretofore possible. New methodology based on the analysis of latent variables allows a separation of within- and between-observer variation for binary measures of assessment among pairs of observers. Maximum likelihood estimation and hypothesis testing are discussed. The methodology is illustrated using data on the assessment of dysplasia by pathologists.

Biometry↗
PubMed1992

Effect of different culture techniques used to induce capacitation on the chromatin stability of human sperm.

To validate an in-vitro bioassay for assessing chromatin stability of human sperm, 38 semen samples from infertile men were studied using sodium dodecyl sulphate, an anionic detergent which disorganizes only the cytoplasmic membrane. Assay sensitivity was 50 sperm, whilst the within- and between-assay variation, and the between-observer variation were found to be within the accepted range for this type of bioassay. The influence of different in-vitro treatments currently used in some clinical assisted fertilization programmes was evaluated: a destabilizing effect occurred in Grade I (stable) and Grade III (swollen) sperm. In the former, all treatments reduced stable sperm; in the latter, a significant (P less than 0.001) increase in swollen sperm was shown with two methods that used Ham's F-10 as culture medium. Different chromatin patterns found in the treated sperm suggest the possibility that the recovered samples could be modified compared to their status at the time of isolation.

Biological Assay↗