Hydrogen-induced microelectronic capacitor failure in pacemakers

Ceramic chip capacitors used in hybrid microelectronics for cardiac pacemakers are usually highly reliable. However, under certain conditions of capacitor construction, capacitor materials, mounting techniques, and environmental conditions, high failure rates may occur. A specific example is presented in which a ceramic capacitor used in an implanted pacemaker delaminated and failed approximately 30 days after being implanted. The failed capacitor caused a pulse rate rise, but due to circuit design techniques, the rate increase was limited to an acceptable value. The capacitor that failed was from an isolated lot of capacitors that was manufactured using pure palladium plates. The circuit containing this capacitor was hermetically sealed within a titanium case by welding. During the welding, a small amount of hydrogen was released from the titanium which, over a period of 2 to 4 weeks, was absorbed by the palladium plates in the capacitor. By absorbing the hydrogen, the palladium plates exhibit a volumetric expansion of sufficient magnitude to crack and delaminate the capacitor to the point of failure. Subsequently, the recurrence of this failure mode has been avoided by using capacitors containing special palladium alloys that cannot absorb hydrogen. This phenomenon is of interest to pacemaker designers since mercury batteries used in conventional pacemakers generate large amounts of hydrogen and potentially may be responsible for complications when used in conjunction with capacitors containing palladium.     

Bacteriocins of Streptococcus bovis

Forty-seven strains of Streptococcus bovis were tested for bacteriocin production. Fourteen were found to produce bacteriocins, while all 47 were sensitive to at least one of these bacteriocins. The bacteriocins, on the basis of their host range on S. bovis strains, formed six groups. A representative of each group was selected and characterized by temperature stability, sensitivity to trypsin and lipase, sedimentation by centrifugation, ability to pass through dialysis tubing, host range on other bacterial species, and conditions for production in liquid media. A correlation between mannitol fermentation and bacteriocin production was noted.     

Immunoreactive growth hormone levels in pigs fed protein or energy restricted diets during the postweaning period

Developmental changes in growth hormone levels during protein or energy malnutrition was studied in weaned pigs. Three or 4 weeks old pigs from control dams were fed a control diet (18% protein), an energy-restricted diet (18% protein) or a low protein diet (6% protein) for 8 weeks. Energy restriction was achieved by feeding the control diet in amounts that allowed very little growth. After the restriction period, all pigs were fed the control diet ad libitum for another 8 weeks. Blood samples were collected at intervals throughout the experiment and the plasma was analyzed for growth hormone by radioimmunoassay. Post weaning protein deprivation resulted in higher growth hormone levels during the restriction period as compared to control pigs or pigs with a restricted energy intake.     

Corticosteroids and avascular necrosis of the femoral head in childhood

The time-course of psychopathological symptoms, of extrapyramidal side effects, and of changes in cerebrospinal fluid (CSF) concentration of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were simultaneously studied during Haloperidol treatment of 14 psychotic patients with chronic organic brain damage. After 15 days of treatment significant antipsychotic effect was found, while Parkinsonism scores in clinical and experimental tests increased only slightly. CSF concentration of HVA increased significantly by 150% compared to the baseline value (p less than 0.05) and 5-HIAA remained unchanged. No correlation was found between the clinical and biochemical variables studied. The comparison of these results with those obtained in patients without brain damage suggests that different psychopathological and extrapyramidal responses to neuroleptics are not strictly associated with specific HVA changes in CSF.     

Pyogenic arthritis of the sacro-iliac joint. Long-term follow-up

Nine cases of sacro-iliac pyarthrosis are presented. The difficulty in localizing the infection is attributable mostly to failure to appreciate the posteriorly situated physical findings. This, and the difficulty with early roentgenographic demonstration of the lesion, may lead to unnecessary abdominal exploration (as in two of our patients) or to prolonged delay in diagnosis and hence spread of the infection. Awareness of the usual physical findings and prompt use of radioisotope scanning to localize the infection led to earlier diagnosis and avoidance of surgery in three patients seen recently. Antibiotic therapy, with or without surgery, led to cure in all patients, with minimum sequelae.     

Affinity chromatography of human plasma and platelet factor XIII on organomercurial agarose

A method for affinity chromatography of plasma and platelet factor XIII has been developed, based on known structural characteristics of these molecules. Plasma factor XIII is composed of a and b subunits which are held together by noncovalent interactions; platelet factor XIII has only a subunits. a subunit contains free sulfhydryl groups, while in b subunit all the cystines form disulfide bonds. The affinity gel is an organomercurial agarose with p-chloromercuribenzoate as the reactive group. Both the zymogen and activated forms of a subunit reversibly bind to the ligand by forming covalent mercaptide bonds and are eluted by reducing agents. b subunit does not bind to the affinity gel and is held to it only through interaction with a subunit. Affinity chromatography can be used to purify plasma and platelet factor XIII and to study interactions of the subunits. Experiments on the affinity chromatography of purified plasma factor XIII in several stages of activation agree with earlier observations that activation is a two-step procedure in which b subunit is not quantitatively released from the complex until the final stage of activation by Ca2+.     

Oropharyngeal control of drinking in rats

Drinking was studied in water-deprived rats with chronic intragastric fistulas. Sham drinking, by which the ingested water was immediately lost through the open gastric fistula, was approximately four times greater than normal drinking. This proportion held across different levels of water deprivation, following 5-ml intragastric preloads of water or isotonic saline or ingestion of isotonic saline. The contribution of oropharyngeal controls in the normal drinking of rats is discussed and is compared with that of other species.     

Persistent thrombin generation in humans during specific thrombin inhibition with hirudin

BACKGROUND: The degree to which antithrombotic drugs suppress thrombin generation is unknown. Because hirudin, unlike antithrombin III, binds intravascular thrombin rapidly and selectively to yield a circulating inactive complex of 3- to 4-hour half-life, we used intravenous hirudin in humans to investigate the course of thrombin generation during and early after anticoagulation with this potent, direct antithrombin. METHODS AND RESULTS: Intravascular thrombin was measured with an ELISA for the thrombin-hirudin complex formed during and for 18 hours after stopping a 6-hour infusion of hirudin at 0.1, 0.2, and 0.3 mg.kg-1.h-1 in three groups of six patients each. With free hirudin in 20- to 10,000-fold molar excess of thrombin and peak activated partial thromboplastin times of 2.3 to 3.0 times baseline, mean plasma thrombin-hirudin complex increased from 794 +/- 85 pg/mL (mean +/- SEM) 15 minutes after the start of the infusion to 1617 +/- 151 pg/mL at 6 hours of infusion to 2667 +/- 654 pg/mL at 24 hours. During the 24-hour observation period, plasma concentration of fragment 1.2 (the peptide released during conversion of prothrombin to thrombin) never fell below baseline but rather increased transiently during the hirudin infusion. Plasma concentrations of thrombin-antithrombin III complex (in ng/mL) decreased from 4.34 +/- 0.40 at baseline to 1.64 +/- 0.13 at 6 hours (P < .001) and gradually increased after stopping the infusion to 5.7 +/- 0.87 at 24 hours (nonsignificant compared with baseline). CONCLUSIONS: Measurement of thrombin-hirudin complex may be used as a marker of thrombin generation in humans. Persistent accumulation of thrombin-hirudin complex and generation of fragment 1.2 during and after completion of potent anticoagulation with hirudin suggest thrombin generation is not blocked by high-affinity thrombin inhibition. The persistent formation of thrombin during declining plasma levels of hirudin may contribute to the pathogenesis of rethrombosis early after antithrombin therapy or during inadequate anticoagulation.