Search PubMed⌕ Search

Biomedical subjects

J Arends

Publications and source records attributed to J Arends.

At least 271 records · Page 15Linked to original sources
PubMed1981

Microchannels in the surface zone of artificially produced caries-like enamel lesions.

In the surfaces zones of artificial carious lesions, tiny microchannels, about 0.5 - 1.5 micrometers in diameter and roughly 100 micrometers in length, have been observed. The mineral components seem to be concentrated at the lumen borders, whereas the organic components have disappeared or are disorganized. These observations suggest that the channels mentioned are involved in the lesion development and play an important role in diffusion (transport) processes taking place between the sub-surface lesion and the liquid phase outside the lesion. The microchannels originate in prisms in the perikymata of the surface enamel. They extend in the direction of the Hunter-Schreger bands, mainly in connection with diazones. No relationship could be found between the microchannels and the direction of the prism sheaths. This indicates that in initial artificial lesion formation the enamel structure plays an important role.

Dental Caries↗
PubMed1980

Hormonal polypeptides and amine metabolites in small cell carcinoma of the lung, with special reference to stage and subtypes.

To elucidate the ectopic hormonal pattern in patients with small cell carcinoma of the lung, plasma ACTH, serum calcitonin, serum gastrin, plasma glucagon, serum insulin, plasma secretin, plasma VIP, serum growth hormone, serum hCG/LH, the total of serum hCG and hCG-beta-subunit,serum alpha-subunit, serum human placental lactogen, urine ADH, urine 5-HIAA, urine VMA, urine HVA, and urine hCG-LH were measured prior to therapy in 75 patients. Twenty-two patients (29%) had elevated plasma ACTH, and 18 of these had concomitant increased values of corticosteroid in a 24-hour urine sample. Forty-eight patients (64%) were found to have elevated serum calcitonin, and one-third of the patients were diagnosed as having the ectopic ADH syndrome. Serum gastrin concentrations were increased in 20% of the patients, but the elevations were marginal in almost all cases. None of the remaining substances was found to be significantly elevated. Concentrations of plasma ACTH, serum calcitonin, and urine ADH were not found to be correlated with the stage of the disease, and no correlation of these substances with the histological subtypes of small cell carcinoma was disclosed.

Adrenocorticotropic Hormone↗
PubMed1980

Increased somatostatin secretion from pancreatic islets of streptozotocin-diabetic rats in response to glucose.

Glucose stimulates somatostatin release from perifused pancreatic islets of diabetic rats 42-47 days after the induction of diabetes, and 48 h after withdrawal of insulin replacement therapy. The glucose effect is augmented by theophylline or glucagon. Basal somatostatin release and glucose-induced secretion are significantly higher in diabetic islets than in controls. It is suggested that glucose promotes somatostatin release by directly interacting with islet D cells but not via indirect pathways. Glucose-induced stimulation appears to be modulated by a D-cell adenylate cyclase/phosphodiesterase system. Reasons responsible for increased somatostatin secretion by diabetic islets include reduction in B-cell mass, suggesting that B cells may normally suppress the secretory activity of D cells.

Animals↗
PubMed1980

Ovarian and placental hormones during prolactin suppression and stimulation in early human pregnancy.

Twenty-seven healthy females referred for legal abortion between the sixth and ninth week of pregnancy were treated for 1 week with either bromocriptine, metoclopramide or placebo. Serum prolactin was significantly (P < 0.01) elevated by metoclopramide and suppressed by bromocriptine. Despite a more than tenfold difference in circulating prolactin levels among these two groups, no significant difference was found in serum levels of progesterone, oestradiol, human chorionic gonadotrophin (hCG) human placental lactogen (hPL) or pregnancy specific B1-glycoprotein (SP1). These data suggest that circulating levels of prolactin below 150 ng/ml are without effect on either luteal or placental hormone secretion during early human pregnancy.

Adult↗
PubMed1980

Progesterone and human chorionic gonadotrophin in serum and pregnandiol in urine in threatened abortion.

Progesterone and human chorionic gonadotrophin (HCG) in serum and pregnandiol in urine were measured in 64 patients admitted to hospital because of threatened abortion. Blood samples were taken and urine specimens collected at regular intervals during admission and after discharge during the rest of the pregnancy. A reference range was worked out for each hormone based on the hormone values obtained from the pregnancies proceeding to term. The predictive significance of values within and below the reference range was determined, for the initial sample and for serial samples. An association between hormone levels and outcome of pregnancy was observed but it is concluded that both single and serial determinations of progesterone and pregnandiol and serial determinations of HCG are unsatisfactory for the evaluation of threatened abortion. However, an initial progesterones value below the reference range and HCG values below 10,000 mIU/ml between the 8th and 15th week of pregnancy was in every case always followed by spontaneous abortion. A hormonal test of fetoplacental origin is recommended for monitoring threatened abortion.

Abortion, Threatened↗
PubMed1980

Microharness and lesion depth studies of artificial caries lesions: a comparison of gelatin and HEC based systems.

Microhardness measurements with the indenter load perpendicular to the artificial carious enamel surfaces can be employed to investigate lesion depth in de- and remineralization of fluoridation studies in vitro or in vivo. In this study, microhardness and lesion depth studies were made on bovine enamel subjected to demineralizing solutions on a gelatin base at pH = 4.5 and 37 degrees C. The parameters studied were load, demineralization period and dialysis of the gelatin. All experimental data are compared with lesions formed in acidified 6% HEC solutions under identical conditions. The results show that lesion formation and mechanical properties of artificially carious enamel are comparable for nonchared HEC and charged gelatin based systems. Because of the higher sensitivity, lesions formed in HEC are to be preferred for lesion depth determinations by means of microhardness indentations. Both gelatin - and HEC based systems show a lesion depth proprotional to the square root of the demineralization period. If gelatin or HEC is dialyzed first, and subsequently used in the demineralizing buffers, the results show that no subsurface lesions are formed but "acid-softening" of the enamel takes place.

Animals↗
PubMed1980

Polarizing microscopy and microradiography of sound enamel.

Plano-parallel longitudinal sections from 19 sound human premolars were imbibed in water and in air. The total birefringence of the occlusal, the midcoronal and the cervical region of the buccal sound enamel cap was then determined. The volume percentage mineral was measured in the same areas using semi-quantitative microradiography. The results show that when the mean values of both water and air imbibed occlusal and midcoronal enamel are considered, there is a positive correlation between the observed total birefringence and the mineral content. The cervical, fissure and cuspal regions showed a poor correlation between mineral content and total birefringence. In longitudinal sections, the influence of the structural organization and the organic matrix is not marked in the occlusal and midcoronal regions although the cervical, fissure and cuspal regions are probably influenced to the greatest extent by these factors.

Air↗
PubMed1979

Purification of peroxidase-conjugated antibody for enzyme immunoassay by affinity chromatography on concanavalin A.

Preparation of peroxidase-conjugated antibody contaminated with very small amounts of unconjugated antibody for highly sensitive enzyme immunoassays is described. The purification process is dependent upon the differential affinity of antibody and peroxidase-conjugated antibody for concanavalin A (Con A). Application of peroxidase and radioactive labelled IgG alone or as a mixture to Con A-Sepharose columns showed that 62-83% of IgG and 0% of peroxidase could be eluted under starting conditions, while 70-83% of peroxidase and about 6% of IgG could be eluted with appropriate buffer. The contamination of the conjugate with unconjugated antibody is dependent on the ratio of conjugated to unconjugated antibody in the mixture to be purified. Using this procedure on IgG conjugated with peroxidase with a ratio of unconjugated to conjugated IgG of about 2 : 1 a preparation was obtained where the ratio was changed to 0.1 : 1.

Antibodies↗