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Biomedical subjects

D Meyer

Publications and source records attributed to D Meyer.

At least 469 records · Page 26Linked to original sources
PubMed1983

Academic stress, power motivation, and decrease in secretion rate of salivary secretory immunoglobulin A.

The effect of academic stress on immune function, as measured by the rate of secretion of salivary secretory immunoglobulin A (s-IgA), was studied prospectively in 64 first-year dental school students. Perceived stress and s-IgA secretion rate were measured five times--during an initial low-stress period, three high-stress periods coinciding with major examinations, and a final low-stress period. The s-IgA secretion rate was significantly lower in high-stress than low-stress periods for the whole group. In addition, personality characteristics differentiated patterns of s-IgA secretion rates. Students characterised by a great need to establish and maintain warm personal relationships secreted more s-IgA at each point than did all other subjects. The s-IgA secretion rates of those with a high inhibited need for power continued to decline through the final low-stress period rather than recovering as in all other subjects.

Adult↗
PubMed1983

Comparative study of various intracervically administered PG gel preparations for termination of first trimester pregnancies.

In a randomized, double-blind study, 30 healthy, nulliparous women of similar gestational age were given intracervical applications of 0.5mg PGE2, 0.05mg Sulprostone or 0.1mg Sulprostone gel in order to soften the cervix prior to curettage for first trimester termination of pregnancy. The preparations were administered 8 hours before curettage. The number of complete and incomplete abortions, ease of passage through the cervical canal, as measured by a tonometer before and 8 hours after the administration of prostaglandin, the degree of pain experienced and the quantity of analgesics required, plus the frequency of systemic side effects were all always assessed by one trialist. With regard to the rate of abortion and cervical softening, the administration of 0.1mg Sulprostone gel proved the most effective method. However, in comparison with the others, it also caused the greatest degree of pain and necessitated the greatest use of analgesics. The softening effect of the prostaglandin E2 gel was significantly less and in this group there were two cases of cervical lesion due to tenaculum laceration. The intracervical application of 0.05mg Sulprostone gel is to be recommended for pre-operative ripening of the cervix before termination of pregnancy in the first trimester, as it effectively dilates the cervix and does not cause systemic side effects or pain in the lower abdomen, enough to make treatment necessary.

Abdomen↗
PubMed1983

Metastatic-adenoid cystic carcinoma of the major salivary glands presenting as a spinal cord tumor.

An adenoid cystic carcinoma (cylindroma) of the submandibular salivary gland presented 17 years after diagnosis with a compressive syndrome of the spinal cord as well as a local recurrence. This is the first reported case of such an occurrence. The literature is reviewed concerning other malignant tumors of the salivary glands presenting in this way. Fifteen cases of mixed salivary-gland tumors are reviewed. Evidence of histologic change from one tumor type to another and the mechanism of spread to the vertebral column is discussed.

Carcinoma, Adenoid Cystic↗
PubMed1983

Heterogeneous abnormalities in the multimeric structure, antigenic properties, and plasma-platelet content of factor VIII/von Willebrand factor in subtypes of classic (type I) and variant (type IIA) von Willebrand's disease.

FVIII/VWF in plasma and platelets was studied by various methods in 16 patients with von Willebrand's disease. These methods included measurements of both VIIIR:Ag and VIIIR:RCo levels, radio-crossed immunoelectrophoresis, analysis of the dose-response curves with both fluid-phase and two-site immunoradiometric assays, and SDS-agarose-acrylamide gel electrophoresis. Studies of normal plasma and platelets by the last-named method disclosed the presence of nine to 10 clearly resolvable bands with molecular weights of approximately 1 to 10 X 10(6) and unresolved higher-molecular-weight material, consistent with the previously described multimeric structure of FVIII/VWF. The multimeric structure and antigenic reactivity of FVIII/VWF were normal in 11 patients with type I von Willebrand's disease. However, measurements of the VIIIR:Ag content in plasma and platelets disclosed the presence of three subgroups. In one (type I-1), the VIIIR:Ag content of both plasma and platelets was decreased; in type I-2, VIIIR:Ag was decreased in plasma but normal in platelets, whereas the reverse was found in two patients with type I-3. In five patients with type IIA von Willebrand's disease we observed various abnormalities in the multimeric structure and antigenic reactivity of FVIII/VWF. The distinguishing features in two patients, designated type IIA-1 and IIA-2, were a decreased amount of high-molecular-weight FVIII/VWF and an impaired antigenic reactivity in both plasma and platelets; the defects in type IIA-2 were qualitatively different and more strikingly abnormal than those in type IIA-1. In three other patients, designated type IIIA-3, a less severe deficit of high-molecular-weight FVIII/VWF in plasma was observed and, in addition, the multimeric structure of FVIII/VWF in platelets was normal. The findings in this study demonstrate that a variety of defects in the synthesis, release, antigenic reactivity, and multimerization of FVIII/VWF are probably responsible for the heterogeneous findings in patients with von Willebrand's disease.

Adult↗
PubMed1982

Evidence that the Ya and Yc subunits of glutathione transferase B (ligandin) are the products of separate genes.

A study of the structure of glutathione transferase B (ligandin) has been made with a view to understanding the relationship between the structures of the subunits of which it is composed. It consists of a mixture of a homodimer (YaYa) and a heterodimer (YaYc) in which the monomers are defined by their apparent molecular weights, that of Ya being 22000 and Yc 25000. Soluble tryptic peptides from the native homodimer YaYa have been compared with those from an artificial homodimer YcYc produced by rehybridization of native YaYc. Approximately 10 peptides specific to YaYa, 12 specific to YcYc and 21 common to both have been detected. Some of the above peptides are derived from variants of the monomers themselves. YaYa and YcYc have two C termini which are the same in both dimers, namely phenylalanine and lysine. Also there are four cysteinyl peptides, of which three are common to YaYa and YcYc and one specific to each. These results suggest that Ya and Yc are derived from at least two different but related genes.

Chemical Phenomena↗
PubMed1982

Pseudo-von Willebrand's disease. An intrinsic platelet defect with aggregation by unmodified human factor VIII/von Willebrand factor and enhanced adsorption of its high-molecular-weight multimers.

Four members (from four generations) of a family with a mild bleeding disorder and intermittent thrombocytopenia had decreased plasma levels of properties related to factor VIII/von Willebrand factor (FVIII/VWF), an absence of high-molecular-weight forms of FVIII/VWF in the plasma (but normal multimeric structure in the platelets), and increased ristocetin-induced platelet aggregation, as in Type IIB von Willebrand's disease. However, unlike the abnormality in FVIII/VWF in Type IIB disease, the basic defect in this family was in their platelets, which absorbed FVIII/VWF high-molecular-weight multimers at lower concentrations of ristocetin than did normal platelets. In addition, either in platelet-rich plasma or suspended in buffer, their platelets were aggregated by unmodified normal human FVIII/VWF without ristocetin. Since the abnormalities of plasma FVIII/VWF in this family may be secondary to the platelet abnormalities, the term "pseudo-von Willbrand's disease" may be suitably descriptive of their disorder.

Adsorption↗
PubMed1982

A micromethod for the measurement of renin in brain nuclei: its application in spontaneously hypertensive rats.

The aim of this study was to develop a method for the measurement of renin activity in small tissue samples obtained from rat brains by the micropunch technique and to investigate the activity of brain renin in spontaneously hypertensive rats. The assay satisfied sensitive and specificity requirements. Angiotensin I was generated at a pH of 6.0; complete recovery of angiotensin I and kinetic studies supported the specificity of the method. Angiotensinase and cathepsin D-like acid protease activity were measured in parallel with renin. Renin was present in all brain regions studied and decreased with the age of the animals. An increased activity of renin was measured in several nuclei of the brain stem and in the neurohypophysis of young hypertensive rats when compared with age-matched normotensive control animals. These differences disappeared in older rats. There was a dissociation between renin and cathepsin D-like acid protease activity. No correlation existed between the distribution of renin and angiotensinase activity. The increased renin activity in brain stem nuclei of spontaneously hypertensive animals is in agreement with previous findings that the brain renin-angiotensin system contributes to the maintenance of high blood pressure in these rats.

Aging↗
PubMed1982

Precipitating anti-VIII:C antibodies in two patients with haemophilia A.

IgG from the plasmas of two haemophilia A patients with anti-VIII:CAg antibodies (1000 and 200 u/ml) was isolated and labelled with 125I. The specific labelled anti-VIII:CAg IgG was further purified by binding to and elution from immobilized factor VIII/von Willebrand factor (F.VIII/vWF). When studied by immunodiffusion and autoradiography, both antibodies gave a precipitin line with normal plasma, serum, cryoprecipitate, purified F.VIII/vWF and the plasmas of two patients with haemophilia A+. No precipitin line was observed with the plasmas of 11 patients with haemophilia A- or four patients with severe von Willebrand's disease. Levels of VIII:CAg obtained by radioelectroimmunoassay were in agreement with those obtained by immunoradiometric assay. This study demonstrates that, contrary to previous evidence, human anti-VIII:CAg antibodies are precipitating as well as neutralizing when studied by highly sensitive techniques.

Antibodies↗
PubMed1982

Abnormal antigenic reactivity of factor VIII/von Willebrand factor subunit in variants of von Willebrand's disease.

Antibodies specific for either the subunit (MW 2.4 X 10(5)) or conformational antigenic determinants of F.VIII/vWF were prepared in order to investigate further the abnormal antigenic reactivity in variants of vWD. Goat anti-human F.VIII/vWF Fab fragments were immunoadsorbed with F.VIII/vWF subunits bound to activated thiol-Sepharose, and the "anti-subunit" antibody was eluted at pH 2.4. Antibodies that did not bind to the beads were designated as "anti-conformation" antibody. The anti-subunit specifically reacted by IRMA with the F.VIII/vWF subunits and with all subunit-containing multimers (MW 4.8 X 10(5) to greater than 15 X 10(6)). The anti-conformation antibody failed to react with F.VIII/vWF subunits but reacted with native (MW 1 to greater than 15 X 10(6)) or partially reduced (MW 4.8 X 10(5)) F.VIII/vWF. It was thus specific for antigenic sites resulting from the association of subunits in dimers or multimers of F.VIII/vWF. In eight patients with a variant of vWD (type IIA), an abnormal antigenic reactivity in plasma, characterized by a dose-response curve not parallel to that of control, was consistently observed by IRMA using the anti-subunit antibody. Six showed a normal dose-response curve with the anti-conformation antibody, and two unique patients also demonstrated an abnormal (nonparallel) response. This study (1) allows the distinction between subunit and conformational antigenic sites on F.VIII/vWF, (2) demonstrates that the decreased antigenicity in type IIA vWD is associated in all cases with an abnormality of F.VIII/vWF subunits and in some patients with an additional defect of polymerization, and (3) further emphasizes the heterogeneity of variants of vWD.

Antibody Formation↗
PubMed1982

[Von Willebrand factor and platelet adhesion to the subendothelium of the vascular wall].

von Willebrand Factor (vWF) is a high molecular weight multimeric (1-20 X 10(6) daltons) glycoprotein which is absent or inactive in von Willebrand's disease (vWD). It is synthesized by the endothelial cell under the control of an autosome and may be released into the blood stream as well as into the subendothelium (SE). vWF is also synthesized by the megacaryocyte and localized in the alpha granules of platelets. Platelet vWF is released during aggregation. Platelets do not adhere to intact endothelial cells but interact with the SE in case of vessel wall injury. vWF plays a key role in platelet adhesion to the SE, especially at high shear rate conditions which prevail in the microcirculation. This function is confirmed by the decreased platelet adhesion observed in either vWD blood (corrected by vWF) or normal blood in the presence of polyclonal or monoclonal antibodies to vWF. The mechanism of platelet adhesion to the SE is still poorly understood. vWF only acts at high shear, ie when the flow rate is elevated and the time of interaction between platelets and the vessel wall is short. This large protein could serve as a "bridge" between the platelet membrane and the SE. It has been shown to bind first to the SE prior to platelet adhesion. Platelet and endothelial cell vWF probably also interact since they may be released in high concentration at the site of injury. The nature of the SE component to which vWF and platelets bind is unknown. Among the candidates are the basement membrane and the collagen fibers (which adsorb vWF), fibronectin, and the microfibrils (which induce vWF-mediated platelet aggregation). It is thus possible that a receptor for vWF exists on one of these components. The ristocetin-induced platelet membrane receptor for vWF seems to be glycoprotein Ib, platelet adhesion being also abnormal in Giant Platelet Syndrome. The in vivo counterpart for ristocetin is unknown, but it is possible that collagen, microfibrils, thrombin (which also induces the platelet receptor for vWF or sialidases (asialo-human vWF is able to directly bind to the platelet membrane) could replace ristocetin. Several sources of data suggest that carbohydrate is important in vWF-platelet interaction.

Animals↗
PubMed1981

[Malignant fibrous histiocytoma after supracondylar femoral fracture (author's transl)].

Supracondylar slanting fracture of the femur was treated by osteosynthesis in a 14-year-old girl. Two months after removal of the plate and screws, 10 months after the initial trauma, a malignant bone tumour in the form of malignant fibrous histiocytoma was diagnosed at the same location after a renewed fracture. The preceding trauma may be assumed to be one of the reasons for occurrence of this rare tumour.

Adolescent↗
PubMed1981

Immunoradiometric assay of factor VIII: coagulant antigen using four human antibodies. Study of 27 cases of haemophilia A.

Immunoradiometric assay (IRMA) of VIII:C antigen was performed using either IgG or monovalent Fab fragments from four antibodies arisen in polytransfused haemophilia A patients (titre between 100 and 1500 U/ml). Using IgG isolated by a solid or a liquid phase system, only the high titre (greater than or equal to 1000 U/ml) antibodies could be used for IRMA, with a sensitivity of 0.2% VIII:CAg. Using Fab fragments isolated by liquid phase, high and low (less than or equal to 150 U/ml) titre antibodies could be used and the IRMA was significantly improved with a 10-fold higher sensitivity. The affinity of the antibodies for VIII:CAg, studied by displacement curves using a modification of the IRMA, was found not to depend upon the titre of the antibody. Comparative levels of VIII:C and VIII:CAg in 27 cases of haemophilia A emphasize the heterogeneity of this disorder, two types of severe and three types of mild haemophilia being observed.

Antibody Affinity↗
PubMed1981

Developmental differences in identifying and discriminating CV syllables.

The purpose of this experiment was to determine whether age-related differences would be observed for identification and discrimination of synthesized, five-formant CV syllables among listeners who showed equal performance scores on a standard clinical test of speech understanding. A second question concerned the relations between performance on identification and discrimination tasks as a function of age. Two 13-item continua that varied in the place of articulation feature ([ba, da, ga]) were used; they differed primarily in the presence of absence of a 5-ms noise burst at the consonant onset. Digitized natural speech syllables were also employed in one experimental task. Strong age effects were obtained for the three tasks--identification of syllables, adaptive estimation of "ba, da-" and "da, ga-" boundaries, and discrimination. With the exception of one condition for six-year-olds, only adults showed significant differences between boundaries and just noticeable differences. Minimal differences were obtained in responses to stimuli with and without initial bursts. Across ages there were no significant differences in the subjects' ability to label the synthesized syllables as compared to the natural speech stimuli. Possible explanations for the observed developmental effects are discussed.

Adult↗
PubMed1981

The effect of hemorrhagic hypotension on urinary kallikrein excretion, renin activity, and renal cortical blood flow in the pig.

We measured urinary kallikrein by its esterolytic and kinin-forming activity in 5-minute urine samples obtained throughout continuous bleeding experiments in pigs to correlate possible changes in urinary kallikrein excretion during hemorrhagic hypotension with resin activity and renal cortical blood flow. Renin activity was determined in venous blood samples and renal cortical blood flow was estimated by the radiolabeled microsphere technique. The rate of urinary kallikrein excretion was increased about 4-fold within an arterial pressure range of 100-70 mm Hg, whereas below 70 mm Hg, arterial pressure urinary kallikrein activity declined to undetectable values. Renin activity was increased only 2-fold in the arterial pressure range between 100 and 70 mm Hg but was increased 4-fold at pressures below 70 mm Hg. The pressure range of 100 to 70 mm Hg corresponded to the autoregulation of renal cortical blood flow and glomerular filtration rate; below that pressure range, renal cortical blood flow dropped to about 10% of the initial value. Therefore, it seems that urinary kallikrein is activated mainly during the period of autoregulation, whereas renin activity is, in the main, increased below the autoregulatory range of pressure. The vasodilatory urinary kallikrein kinin system might be involved in maintaining sufficient local blood flow during autoregulation whereas a decrease in blood pressure below the autoregulatory range leads to a major increase in renin activity, thus illustrating the attempt of the organism to reestablish sufficient blood pressure to maintain autoregulation.

Animals↗