An alternate model of thyroid cytology: practical not perfect

A sample of 384 thyroid cytology specimens prepared by cytospin over a 2.5-year period was classified by original report into inadequate, non-neoplastic and suspicious of neoplasia or worse. This was then compared with subsequent histology. The resulting data showed an inadequacy rate of 33%, a sensitivity of 55%, a specificity of 59%, a positive predictive value of 64% and a negative predictive value of 93%. On review of the cytology, in knowledge of the subsequent histology, the maximum achievable results were determined to have a positive predictive value of 79% and a negative predictive value of 97%. No clinically significant adverse event was detected.     

Partitioning of water resources among plants of a lowland tropical forest

Source water used by plants of several species in a semi-evergreen lowland tropical forest on Barro Colorado Island, Panama, was assessed by comparing the relative abundance of deuterium, D, versus hydrogen, H (stable hydrogen isotope composition, D) in xylem sap and in soil water at different depths, during the dry season of 1992. Ecological correlates of source water were examined by comparing xylem water D values with leaf phenology, leaf water status determined with a pressure chamber, and rates of water use determined as mass flow of sap using the stem heat balance method. Soil water D values decreased sharply to 30 cm, then remained relatively constant with increasing depth. Average D values were-13, for 0–30 cm depth and-36.7 for 30–100 cm depth. Soil water D values were negatively associated with soil water content and soil water potential. Concurrent analyses of xylem water revealed a high degree of partitioning of water resources among species of this tropical forest. Xylem water D of deciduous trees (average=-25.3±1.4) was higher than that of evergreen trees (average=-36.3±3.5), indicating that evergreen species had access to the more abundant soil water at greater depth than deciduous species. In evergreen shade-tolerant and high-light requiring shrubs and small trees, D of xylem water was negatively correlated with transpiration rate and leaf water potential indicating that species using deeper, more abundant water resources had both higher rates of water use and more favorable leaf water status.     

Protein-protein interactions in blood clotting. The use of polarization of fluorescence to measure the dissociation of plasma factor XIIIa.

1. Human plasma Factor XIII (the precursor of fibrin-glutamine-fibrin-lysine endo-gamma-glutamyltransferase) was randomly labelled by incubation with fluorescein isothiocyanate. The biochemical properties of the system were unaltered by the label. The polarization of the fluorescein fluorescence attached to the plasma protein was measured and the following conclusions were reached. 2. Factor XIII (a'2b2) does not dissociate in the protein-concentration range 10-500 microgram/ml either with or without added Ca2+. 3. Factor XIIIa (a'2b2) does not dissociate in the absence of Ca2+ in the protein-concentration range 10-500 microgram/ml. 4. Additions of Ca2+ to Factor XIIIa result in a decreased polarization of fluorescence as the tetramer dissociates. The decrease in polarization was the same amplitude at protein concentrations 10-500 microgram/ml and Ca2+ concentrations 2-66 mM and indicates that the overall process is essentially irreversible. The decrease in polarization consisted of fast and slow exponential phases. Both the rate of the fast phase and the proportion of the reaction it represented increased with Ca2+ concentration. 5. A comparison of the rate of dissociation measured by fluorescence polarization and the rate of appearance of enzyme activity in the presence of a protein substrate suggests that the Factor XIII is autoactivated by a soluble a-subunit-containing molecular forming a tight complex with the substrate.     

A new variety of spondyloepiphyseal dysplasia characterized by punctate corneal dystrophy and abnormal dermal collagen fibrils

Summary Several individuals from one family are described with a unique form of spondyloepiphyseal dysplasia. Characteristic features include shorttrunked short stature, punctate corneal dystrophy and marked disorganization of dermal collagen fibrils when examined by transmission electron microscopy. Inheritance is compatible with either dominance and a variable expression or X-linkage. Although the basic defect has not been determined, the tissue distribution is consistent with a defect in a non-collagenous component that affects collagen fibril formation or stability.     

Calcium regulation of growth and differentiation of mouse epidermal cells in culture

Modification of the ionic calcium concentration in the culture medium markedly alters the pattern of proliferation and differentiation in cultured mouse epidermal cells. When medium calcium is lowered to 0.05--0.1 mM, keratinocytes proliferate rapidly with a high growth fraction and do not stratify, but continue to synthesize keratin. The cells grow as a monolayer for several months and can be subcultured and cloned in low Ca++ medium. Ultrastructural examination of cells cultured under low Ca++ conditions reveals widened intercellular spaces, abundant microvilli and perinuclear organization of tonofilaments and cellular organelles. Desmosomes are absent. Epidermal cells growing as a monolayer in low Ca++ can be induced to terminally differentiate by adding calcium to the level normally found in the culture medium (1.2 mM). Cell-to-cell contact occurs rapidly and desmosomes form within 2 hr. The cells stratify by 1--2 days and terminally differentiate with cell sloughing by 3--4 days. After Ca++ addition, DNA synthesis decreases with a lag of 5--10 hr and is totally inhibited within 34 hr. In contrast, RNA and protein synthesis continue at 40--50% of the low Ca++ level at day 3, a time when many cells are detaching from the culture dish. Keratin synthesis is unaffected by the Ca++ switch.     

The multiple complexes formed by the interaction of platelet factor 4 with heparin.

The anisotropy of the fluorescence of dansyl (5-dimethylaminonaphthalene-1- sulphonyl) groups covalently attached to human platelet factor 4 was used to detect the macromolecular compounds formed when the factor was mixed with heparin. At low heparin/protein ratios a very-high-molecular-weight compound (1) was formed that dissociated to give a smaller compound (2) when excess heparin was added. 2. A large complex was also detected as a precipitate that formed at high protein concentrations in chloride buffer. It contained 15.7% (w/w) polysaccharide, equivalent to four or five heparin tetrasaccharide units per protein tetramer. In this complex, more than one molecule of protein binds to each heparin molecule of molecular weight greater than about 6 X 10(3).3. The stability of these complexes varied with pH, salt concentration and the chain length of the heparin. The limit complexes found in excess of the larger heparins consisted of only one heparin molecule per protein tetramer, and the failure to observe complexes with four heparin molecules/protein tetramer is discussed.     

NADH binding to porcine mitochondrial malate dehydrogenase.

The binding of NADH to porcine mitochondrial malate dehydrogenase in phosphate buffer at pH 7.5 has been studied by equilibrium and kinetic methods. Hyperbolic binding was obtained by fluorimetric titration of enzyme with NADH, in the presence or absence of hydroxymalonate. Identical results were obtained for titrations of NADH with enzyme in the presence or absence of hydroxymalonate, measured either by fluorescence emission intensity or by the product of intensity and anisotropy. The equilibrium constant for NADH dissociation was 3.8 +/- 0.2 micrometers, over a 23-fold range of enzyme concentration, and the value in the presence of saturating hydroxymalonate was 0.33 +/- 0.02 micrometer over a 10-fold range of enzyme concentration. The rate constant for NADH binding to the enzyme in the presence of hydroxymalonate was 3.6 X 10(7) M-1 s-1, while the value for dissociation from the ternary complex was 30 +/- 1 s-1. No limiting binding rate was obtained at pseudo-first order rate constants as high as 200 s-1, and the rate curve for dissociation was a single exponential for at least 98% of the amplitude. In addition to demonstrating that the binding sites are independent and indistinguishable, the absence of effects of enzyme concentration on the KD value indicates that NADH binds with equal affinity to monomeric and dimeric enzyme forms.     

DISAGGREGATION OF POLYSOMES IN FETAL ORGANS AND MATERNAL BRAIN AFTER ADMINISTRATION OF d-LYSERGIC ACID DIETHYLAMIDE IN VIVO

The intravenous administration of d-lysergic acid diethylamide (LSD) to pregnant female rabbits induced hyperthermia as well as disaggregation of polysomes in fetal organs and maternal brain. The LSD-induced polysome shift in maternal brain and fetal organs was not due to an activation of ribonuclease or associated with alterations in the levels of free amino acids. Pretreatment with the receptor blocking agents haloperidol and pizotyline blocked both LSD-induced polysome shift in maternal brain and fetal organs and LSD-induced hyperthermia. Fine dissection of adult rabbit brain showed that the extent of LSD-induced disaggregation of polysomes does not exhibit any marked regional variation.