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Biomedical subjects

J B Hazelrig

Publications and source records attributed to J B Hazelrig.

At least 19 recordsLinked to original sources
PubMed1993

A mathematically defined motif for the radial distribution of charged residues on apolipoprotein amphipathic alpha helixes.

Multiple amphipathic alpha-helical candidate domains have been identified in exchangeable apolipoproteins by sequence analysis and indirect experimental evidence. The distribution of charged residues can differ within and between these apolipoproteins. Segrest et al. (Segrest, J. P., H. DeLoof, J. G. Dohlman, C. G. Brouillette, and G. M. Anantharamaiah. 1990. Proteins. 8:103-117.) argued that these differences are correlated with lipid affinity. A mathematically defined motif for the particular charge distribution associated with high lipid affinity (class A) is proposed. Primary sequence data from protein segments proposed previously to have an amphipathic alpha-helical structure are scanned. Counting formulas are presented for determining the conditional probability that the match between an observed charge distribution and the proposed motif would occur by chance. Because the preselected helical segments are short (the modal length is 22) and the motif definition imposes multiple constraints on the acceptable distributions, the computer-based algorithm is quite feasible computationally. 19 of the 20 segments previously assigned to class A match the motif sufficiently well (the remaining one is borderline), while very few others "erroneously" pass the screening test. These results confirm the original assignments of the candidate domains and, thus, support the hypothesis that there is a distinguishable subset of helixes having high lipid affinity. This counting approach is applicable to a growing subset of protein sequence analysis problems in which the segment lengths are short and the motif is complex.

Apolipoproteins↗
PubMed1992

Fractal dimension from radiographs of peridental alveolar bone. A possible diagnostic indicator of osteoporosis.

The purpose of this study was to investigate whether a radiographic estimate of osseous fractal dimension is useful in the characterization of structural changes in alveolar bone. Ten dry mandibular bone segments were radiographed from three controlled projection angles (-5, 0, +5 degrees), before and after acid-induced partial decalcification. Fractal dimension was estimated by regression analysis of power spectra computed by Fourier transform of selected regions of interest in digitized images of the radiographs. Repeated-measures ANOVA showed that fractal dimension so determined varied over anatomic locations (p less than .01), but increased after acid-induced demineralization (p less than .0005), irrespective of the radiographic projection angles (p greater than .99). In vivo fractal dimension was computed from randomly selected intraoral radiographs of six premenopausal (ages, 32.8 +/- 3.9) and six postmenopausal (ages, 62.5 +/- 4.1) women. A significantly (p less than .01) higher fractal dimension was observed in the older group.

Adult↗
PubMed1992

Turnover of synthetic class A amphipathic peptide analogues of exchangeable apolipoproteins in rats. Correlation with physical properties.

Peptide analogues of the class A amphipathic helixes from exchangeable apolipoproteins mimic apolipoprotein (apo) A-I in a number of ways, including the ability to activate the enzyme lecithin:cholesterol acyltransferase, to associate with high density lipoproteins (HDLs), and to form HDL-like particles in the presence of lipids. This study investigated the metabolic properties of several of these peptide analogues in the rat. Peptide analogues studied were 18A (referred to as L-18A to differentiate it from D-18A, and which mimics apolipoprotein amphipathic helical domains in its charge distribution), 37pA (a dimer of two 18A monomers separated by a proline), 18R (with reversed charge distribution compared with 18A), and D-18A (identical in amino acid sequence to 18A but synthesized from D-amino acids). Peptides were radiolabeled with 125I. In addition, metabolism of rat and human 125I-apo A-I and human 14C-apo A-I was studied; no significant differences in clearance of these preparations were seen. Clearance data were fitted to multiexponential equations to give half-times of clearance; biexponential equations consistently provided the best nonlinear least-squares curve fit. The order of relative lipid affinity determined in vitro was 37pA greater than apo A-I greater than D-18A = L-18A greater than 18R. Half-times of clearance were in the same approximate rank order: 37pA, 6.9 +/- 3.3 hours (mean +/- SD); apo A-I, 6.9 +/- 1.8 hours; D-18A, 4.0 +/- 1.0 hours; L-18A, 4.6 +/- 1.6 hours; and 18R, 0.9 +/- 0.1 hour.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1989

Glycemic responses in insulin-dependent diabetic patients: effect of food composition.

This study examined the hypothesis that the glucose component of food and not the total carbohydrate is the major determinant of the glycemic response in patients with insulin-dependent diabetes mellitus. Patients were given glucose alone, fructose alone, glucose + fructose, lactose, and glucose + fat + protein. Fructose given alone increased the blood glucose almost as much as a similar amount of glucose (78% of the glucose-alone area, p less than 0.05). However, the same amount of fructose given with glucose produced no greater glycemic response than did glucose alone (108%). Similarly, galactose contributed only slightly to the glycemic response when given as lactose (122%, p less than 0.01) whereas protein and fat had no additional glycemic effect (101%). To test the above hypothesis in natural foods, patients were fed an amount of bread (high glycemic index) or apple (low glycemic index) that contained 25 g glucose. Both challenges produced glycemic responses very similar to 25 g purified glucose.

Adult↗
PubMed1984

Variability in three morphologic features of the permanent maxillary central incisor.

Variability in tooth morphology can play a significant role in appliance design and the achievable results of orthodontic treatment. This investigation was undertaken to determine quantitatively the variation in three anatomic features of the maxillary central incisor. The three features are the crown-root angulation in a labiolingual direction, the angle formed by a tangent to the middle of the labial surface of the crown and the long axis of the crown from a proximal view, and the lingual curvature of the crown from a proximal view. Tracings of maxillary central incisors were made from two different sources. The first source consisted of radiograms of 98 extracted central incisors, and the second source was a group of 100 cephalometric radiograms which were part of pretreatment records of patients in the Orthodontic Department. The cephalometric radiograms included 25 Angle Class I, 25 Class II, Division 1, 25 Class II, Division 2, and 25 Class III malocclusions. The first measurement taken was the angle formed by the long axis of the crown and the long axis of the root. The second measurement was the angle formed by the long axis of the crown and a tangent to the midpoint of the labial surface of the crown. For the third measurement, the lingual curvature of the crown was described by a mathematical equation whose parameters were used for comparisons. The results revealed a wide range of variation in the three features measured. The mean crown-root angle for Class II, Division 2 malocclusions differed significantly from that for Class II, Division 1 and Class III malocclusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalometry↗
PubMed1983

Transient focal ischemia in subhuman primates. Neuronal injury as a function of local cerebral blood flow.

Unilateral, transient (30, 60, and 120 minutes (min)) middle-cerebral-artery (MCA) occlusion was induced via transorbital craniotomy in 11 waking subhuman primates. Local cerebral blood flow (LCBF) was calculated from hydrogen clearance curves obtained through the use of intracerebral platinum microelectrodes. Unilateral MCA occlusion decreased LCBF in the territory of the ipsilateral MCA. Within minutes of the arterial occlusion all monkeys developed contralateral neurologic deficits that began disappearing three hours (h) after reopening the MCA. Regional ischemia, followed by 24 h of reperfusion, produced varying degrees of tissue vacuolation which correlated (r = 0.60, p less than 0.01, n = 49) with the percent reduction in LCBF multiplied by the occlusion time. Neurons were classified according to the structural features of their perikaryon. A plot of neuron types versus percent vacuolation suggested that normal neurons become increasingly scalloped under increasingly severe ischemic conditions. The number of scalloped neurons decreased precipitously in areas of marked sponginess coincident with the appearance of irreversibly damaged neurons. Local tissue edema values exceeding 30% correlated with irreversible injury to all neurons in the same area. Regional cerebral ischemia of increasing severity was acompanied by increasing numbers of lethally injured neurons.

Animals↗
PubMed1979

Survival and probability of cure without and with operation in complete atrioventricular canal.

Actuarial analysis based on postmortem examination of patients who had been treated nonsurgically for complete atrioventricular (A-V) canal defect shows that only 54% survive to 6 months of age, 35% to 12 months, 15% to 24 months, and 4% to 5 years of age. Our surgical experience since 1975 in 39 patients confirms the idea that primary repair is feasible in small infants. The highest risk of hospital death is when the operation is done in the early months of life; it falls to 17% by age 12 months. Between 1967 and October, 1976, the five-year survival rate among patients leaving the hospital alive after repair was 91%. The age-specific probability of "surgical cure" of patients operated upon for complete A-V canal (alive five years later with mean pulmonary artery pressure less than 25 mm Hg) is maximal at 73% when the operation is done at about 14 months of age. Urgent earlier repair is frequently necessitated by the life history of the disease.

Age Factors↗
PubMed1978

Life expectancy without surgery in tetralogy of Fallot.

All published autopsy cases of patients with tetralogy of Fallot who died without surgical treatment were studied to determine the life expectancy of such persons. In addition, the data from a study of persons with tetralogy alive in Denmark in 1949 were reanalyzed. The survival data from these two sources were remarkably similar, indicating that 66 percent of persons with tetralogy of Fallot not treated surgically live to age 1 year, 49 percent to age 3 years and 24 percent to age 10 years; thereafter, the hazard function (or instantaneous risk of death) remains constant. The chance of survival is significantly less when pulmonary atresia, rather than stenosis, is present.

Adolescent↗