A functional factor X deficiency

A functional factor X deficiency is described which caused pronounced reduction in the in vitro activation of the extrinsic system while marginally affecting the in vitro activation of the intrinsic pathway. All studies were normal with the exception of a prolonged PT, an elevated factor X antigen, and low factor X activity. Western blot analysis revealed the presence of two factor X species. The abnormal molecule was of higher molecular weight. Interestingly, there was no bleeding associated with this deficiency. The biochemical basis of this defect is currently under investigation.

Pseudothrombocytopenia in plateletpheresis donors

BACKGROUND

EDTA pseudothrombocytopenia (PTCP) is an in vitro artifact in which the anticoagulation of blood with EDTA is associated with in vitro agglutination of platelets, resulting in a spuriously low platelet count. In apheresis donors, whole-blood samples for complete blood counts are routinely drawn into tubes anti-coagulated with EDTA.

STUDY DESIGN AND METHODS

Records of apheresis donors were examined to identify persons in whom the postdonation counts were less than 100 x 10(9) per L. Identified donors were studied to confirm the presence of PTCP by drawing blood samples into EDTA, heparin, and trisodium citrate for serial platelet counts at room-temperature incubation. Platelet counts in citrated plasma were measured before and after the addition of EDTA. A single HLA-matched component from an identified PTCP donor was monitored for response by corrected count increment in the recipient.

RESULTS

A total of nine donations were identified, involving 2 donors from a population of 945 donors (prevalence 0.2%). On testing, both donors were confirmed to have PTCP. The addition of EDTA to citrated plasma did not affect the platelet count. Response in a recipient to an HLA-matched component showed an acceptable corrected count increment.

CONCLUSION

PTCP may occur in plateletpheresis donors and result in needless medical referral or donor deferral. PTCP does not appear to alter the yield content of the component or to be passively transferred to a recipient.

Auditory brainstem responses after ovariectomy and estrogen replacement in rat

Previous work has suggested possible influences of ovarian hormones on evoked potentials in the auditory system. The aim of this project was to study the effects of ovariectomy and subsequent administration of estrogen replacement on the auditory brainstem response and the middle latency response. Groups of 90 day-old Long-Evans hooded rats were anesthetized for bilateral ovariectomies (ovex) and recordings made 3 weeks later. During the week prior to recordings some ovariectomized groups received subcutaneous injections of 10, 100 or 500 micrograms/kg Premarin in peanut oil, and other unoperated animals received vehicle injections. Recordings from vertex/chin using needle electrodes and pure tone stimulus parameters were made under Rompun/Ketamine. The results using 40 kHz tone stimuli showed that mean latencies for ovex animals were longer than animals in the 100 micrograms/kg Premarin group for waves 1a, 1an, 1b, 11, 111, 111n, and 1V/V. Other posthoc comparisons at 40 kHz stimulation revealed differences between control and 100 micrograms/kg Premarin groups for latencies of waves 1b, 1bn, 11 and 111. Latency reduction appeared for waves 1b, 1bn, 11 and 111 for the 10 ovex group, but only at wave 11 for the 500 ovex group, compared to ovex-only animals. Data from 8 kHz stimulation also demonstrated significant differences between the ovex and ovex 100 groups at waves 1bn and Vn. Observations of interpeak latency differences, especially between waves 1a and 11, suggested central as well as cochlear involvement in hormone action.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemostatic effects of stress hormone infusion

BACKGROUND

Surgery causes changes in hemostasis, leading to a hypercoagulable state. This postoperative increase in hemostatic function is attenuated in patients receiving regional anesthesia compared with those receiving general anesthesia. Regional anesthesia also decreases the neuroendocrine response to surgery compared with general anesthesia, and this effect is hypothesized to be responsible for the differences in hemostatis. To test the hypothesis that neuroendocrine hormones cause changes in hemostasis, we infused stress hormones into normal volunteers and measured hemostatic function.

METHODS

After drug screening, 12 normal volunteers were studied. On two admissions, volunteers randomly received either stress hormone (epinephrine, cortisol, or glucagon) or placebo infusion for 24 h. During infusion, patients remained at bed rest and received controlled meals. Blood was obtained from indwelling venous catheters before infusion and 2, 8, and 24 h after the start of infusion. Blood was analyzed for neuroendocrine hormone concentrations, glucose, complete blood count, coagulation proteins, platelet reactivity, and activity of the fibrinolytic system.

RESULTS

In the stress hormone group, concentrations of epinephrine, norepinephrine, cortisol, glucagon, and insulin were increased during the infusion period compared with those in the placebo group. Glucose concentrations and white blood cell counts were increased in the stress hormone group compared with those in the placebo group. Circulating fibrinogen concentrations increased 30% and ex vivo collagen-induced platelet reactivity increased 123% (aggregation) and 103% (dense granule release) in the stress hormone infusion group, whereas there was no change in the placebo group. Fibrinolytic proteins were similar in both groups, demonstrating a decrease in plasminogen activator inhibitor-1 activity at 8 and 24 h (196% in the hormone group vs. 199% in the placebo group).

CONCLUSIONS

Infusion of stress hormones to concentrations found during surgery is safely tolerated and causes metabolic changes observed with surgery. Stress hormone infusion increases ex vivo platelet reactivity and fibrinogen concentrations that resemble changes seen postoperatively but does not recreate the postoperative decrease in fibrinolytic activity. Differences in neuroendocrine response between types of anesthesia may explain some postoperative changes in platelet function and acute phase reactivity, but additional uncharacterized factors are responsible for the differences in fibrinolysis.

Age-related changes in beta-adrenergic neuroeffector systems in the human heart

BACKGROUND

Aging decreases cardiac beta-adrenergic responsiveness in model systems and in humans in vivo. The purpose of this study was to comprehensively evaluate the age-related changes in the beta-receptor-G protein-adenylyl cyclase complex in nonfailing human hearts.

METHODS AND RESULTS

Twenty-six nonfailing explanted human hearts aged 1 to 71 years were obtained from organ donors and subjected to pharmacological investigation of beta-adrenergic neuroeffector systems. When the population was subdivided into the 13 youngest and 13 oldest subjects, total beta-receptor density assessed by maximum [125I]ICYP binding (beta max) was reduced in older hearts by 37% in left ventricles and 31% in right ventricles (both P < .05), and the downregulation was confined to the beta 1 subtype (r = .78 left ventricle beta 1 density versus donor age). Older donor hearts exhibited a 3- to 4-fold rightward shift of ICYP-isoproterenol (ISO) competition curves and demonstrated 43% fewer receptors in a high-affinity agonist binding state (P < .05). Older hearts exhibited decreased adenylyl cyclase stimulation by ISO, by zinterol (beta 2-agonist), and by the G protein-sensitive probes forskolin, Gpp(NH)p, and NaF. In contrast, there was no change in response to manganese, a specific activator of the adenylyl cyclase catalytic subunit. Toxin-catalyzed ADP ribosylation in membranes prepared from older versus younger hearts revealed a 29% to 30% reduction (P < .05) with cholera toxin (Gs) but no difference with pertussis toxin (Gi). The systolic contractile response of isolated right ventricular trabeculae to ISO was decreased by 46%, with a 10-fold increase in ISO EC50 in older relative to younger donor hearts.

CONCLUSIONS

There is a profound decrease in cardiac beta-adrenergic responsiveness with aging. This occurs by multiple mechanisms including downregulation and decreased agonist binding of beta 1-receptors, uncoupling of beta 2-receptors, and abnormal G protein-mediated signal transduction.

The effects of bedrest on circadian changes in hemostasis

Venous stasis occurs when people are at bedrest, because of altered venous flow characteristics. This is commonly believed to be one etiology behind the development of deep venous thrombosis (DVT). The hemostatic effects of bedrest and their possible role in DVT development have not been fully examined. We hypothesized that bedrest would lead to increases in hemostatic function and that these increases could be important in the development of DVT. Twelve non-smoking volunteers were studied during supine positioning for 36 hours. Platelet reactivity and plasma concentrations of fibrinogen, alpha 2-antiplasmin, plasminogen, thromboxane beta 2, plasminogen activator inhibitor-1, tissue plasminogen activator and neuroendocrine hormones (cortisol, epinephrine and norepinephrine) were measured at 8:00 a.m., 10:00 a.m., 4:00 p.m. and 8:00 a.m. Cortisol demonstrated an early morning increase while catecholamines were unchanged throughout. Fibrinogen, alpha 2-antiplasmin, plasminogen and platelet reactivity were no different at any time point. Fibrinolytic proteins changed over time, manifested by decreased PAI-1 antigen and activity levels at 24 h. Based upon the parameters measured, bedrest causes no increase in hemostatic function. In fact, bedrest causes the potential for enhanced fibrinolysis, that differs from that previously reported for normal activity over 24 h. This may represent a protective mechanism to counter the effects of stasis from bedrest.

Use of molecular probes and PCR for detection and typing of Leishmania--a mini-review

The use of molecular tools to detect and type Leishmania species in humans, reservoirs or sandflies has been pursued using different approaches. The polymerase chain reaction provided sensitivity to case this task, since the use of hybridization procedures alone employing specific probes is hampered due to the low detection limit. In this report, we describe the different molecular targets used in our laboratory, aiming at the detection and specific typing of these protozoa. Different kits based on hybridization assays and PCR amplification using kinetoplast and nuclear targets are described and the results obtained from their use are reported.

Are we doing too many animal biodisposition investigations before phase I studies in man? A re-evaluation of the timing and extent of ADME studies

This commentary attempts to re-evaluate, from a scientific standpoint, the timing and usefulness of undertaking detailed kinetic and metabolic studies in many animals from several species, and extrapolating the findings to man. This reappraisal is now possible due to the conditional acceptance of harmonised guidelines on toxicokinetics at ICH2 in Orlando in 1993, the results from which can provide much of the information that is required to design and validate safety studies and to extrapolate exposure or safety margins to man.

Long-term neuropsychological sequelae of fever associated with amnesia

It has been well established that high fever can cause substantial damage to the cerebellum and also cause multiple small vascular lesions in neocortex and subcortical white matter. Beyond acute effects, the neuropsychological sequelae of these latter cortical and subcortical lesions have not been studied. The investigation reported involved 36 VA patients with a history of serious febrile illness. The febrile illnesses of the pyrexic subjects did not cause febrile seizures and resulted from diseases that did not directly involve the brain (e.g., encephalitis, meningitis, malaria). Control subjects were combat veterans who had suffered gunshot wounds, but who had no history of febrile illness. Pyrexic patients performed worse than controls on a variety of measures including language, memory, concentration, and word finding as well as failing a test of dichotic listening for words. Results demonstrate that hyperpyrexia can have lasting neuropsychological sequelae, and suggest that history of serious febrile illness be considered as an exclusionary criterion for participation in neuropsychological research concerning other topics or disorders.

Ligand for FLT3/FLK2 receptor tyrosine kinase regulates growth of haematopoietic stem cells and is encoded by variant RNAs

The FLT3/FLK2 receptor tyrosine kinase is closely related to two receptors, c-Kit and c-Fms, which function with their respective ligands, Kit ligand and macrophage colony-stimulating factor to control differentiation of haematopoietic and non-haematopoietic cells. FLT3/FLK2 is thought to be present on haematopoietic stem cells and found in brain, placenta and testis. We have purified to homogeneity and partially sequenced a soluble form of the FLT3/FLK2 ligand produced by mouse thymic stromal cells. We isolated several mouse and human complementary DNAs that encode polypeptides with identical N termini and different C termini. Some variants contain hydrophobic transmembrane segments, suggesting that processing may be required to release soluble ligand. The purified ligand enhances the response of mouse stem cells and a primitive human progenitor cell population to other growth factors such as interleukins IL-3 and IL-6 and to granulocyte-macrophage colony-stimulating factor, and also stimulates fetal thymocytes.

Use of Drosophila mutants to distinguish among volatile general anesthetics

The way general anesthetics cause their clinically useful effects on the nervous system is not known. Since the principal determinant of the potency of these agents is their solubility in oil, the role of chemical structure in affecting anesthetic targets has been obscured. In this work, we use an intense beam of light (Tinklenberg, J. A., Segal, I. S., Tianzhi, G. & Maze, M. (1991) Ann. N.Y. Acad. Sci. 625, 532-539) to assess the effect of general anesthetics on the capacity of fruit flies to sense a noxious stimulus and respond to it. By examining the effect of halothane-resistant (har) mutations on the potency of various volatile anesthetics in this assay, we establish similarities and differences between these agents that highlight the was chemical structure influences anesthetic action. In general, the potencies of anesthetics with different chemical structure are affected to different extents by one or more har mutations. However, three anesthetics of related structure (enflurane, isoflurane, and desflurane) show quantitatively indistinguishable alterations in potency in each of four genetic tests. These results not only identify important structural features of anesthetics but also place limits on the classical view that all anesthetics act at a common target.

Venous embolization after deflation of lower extremity tourniquets

Massive pulmonary embolism has been reported to occur with the use of lower extremity tourniquets. We used transesophageal echocardiography to determine the incidence of venous embolism during lower extremity orthopedic surgery performed with a pneumatic tourniquet. The hemodynamic and respiratory consequences of all embolic events were assessed. Venous emboli were detected after tourniquet deflation in 8 of 30 procedures. The incidence of embolism was unrelated to the type of surgical procedure performed or the duration of tourniquet inflation. There were no significant differences in preoperative characteristics or postdeflation hemodynamic and respiratory responses between patients with and without emboli. Venous embolization is a relatively common event after tourniquet deflation. The clinical significance of these events remains to be determined.

Antibodies to murine CD40 stimulate normal B lymphocytes but inhibit proliferation of B lymphoma cells

A rat anti-mouse CD40 antiserum has been prepared by hyperimmunisation of Lewis rats with a highly purified preparation of the recombinant extracellular domain of murine CD40. This antiserum specifically binds CD40-expressing L cell transfectants, but not untransfected L cells, and induces vigorous proliferation of highly purified small dense B cells obtained from the spleens of unstimulated mice. Anti-CD40-induced B cell proliferation can be augmented by the addition of IL-4 and is inhibited by purified recombinant soluble mouse CD40. Interestingly the same anti-CD40 antiserum specifically inhibits the in vitro growth of A.20 murine B lymphoma cells. The specificity of this inhibition can be demonstrated by reversing the effect with purified recombinant soluble mouse CD40. These data implicate CD40 as a possible target for therapeutic intervention in the treatment of B lymphomas.

Initial effects of the grounding of the tanker Braer on health in Shetland. The Shetland Health Study Group

OBJECTIVE

To determine if the oil spillage from the tanker Braer had any immediate health effects on the exposed resident population.

DESIGN

Cohort study with a comparison against controls, exposure status being assigned on the basis of geographical location.

SETTING

Rural Shetland.

SUBJECTS

All those resident on or after 5 January 1993 (day 0) within 4.5 km of the site of tanker's grounding. Controls matched for sex and age were drawn from a general practice list 95 km distant.

OUTCOME MEASURES

Demographic details; smoking and alcohol consumption; perception of health and reported presence or absence of specific symptoms; peak expiratory flow; results of haematology, liver and renal function tests, and blood and urine toxicology.

RESULTS

Of subjects contacted, 420 (66%) exposed people and 92 (68%) controls were studied; 56 non-attenders were surveyed. Principal health effects arose on days 1 and 2 and were headache, throat irritation, and itchy eyes. No significant differences between those exposed and controls were found for any of the biological markers. Toxicological studies did not show any exposures that are known to affect human health.

CONCLUSIONS

The study confirmed the anecdotal reports of certain acute symptoms. No evidence of pulmonary, haematological, renal, or hepatic damage was detected at the population level. Toxicological samples from exposed people did not find levels known to affect human health. Further studies are required to ascertain whether there have been any long term effects on the population.

Helping people help themselves

With the growing consumer participation movement and the emphasis in health care shifting from hospital to community, the term community development is cropping up more and more. Yet the concept of community development has always been integral to public health nursing. Simply put, community development is a process by which a community identifies its needs and assumes ownership of decision-making and subsequent action surrounding those needs. By integrating community development principles into their work with two neighboring communities, nurses with Calgary Health Services facilitated the establishment of a much-needed parent support group.

Networking with mitogen-activated protein kinases

Mitogen activated protein (MAP) kinases and their target ribosomal protein S6 (RSK) kinases have been recognized as shared components in the intracellular signaling pathways of many diverse cytokines. Recent studies have extended this protein kinase cascade by identifying the major activator of vertebrate MAP kinases as a serine/threonine/tyrosine-protein kinase called MEK, which is related to yeast mating factor-regulated protein kinases encoded by the STE7 and byr1 genes. MEK, in turn, may be activated following its phosphorylation on serine by either of the kinases encoded by proto-oncogenes raf1 or mos, as well as by p78mekk, which is related to the yeast STE11 and byr2 gene products. Isoforms of all of these protein kinases may specifically combine to assemble distinct modules for intracellular signal transmission. However, the fundamental architecture of these protein kinase cascades has been highly conserved during eukaryotic evolution.

Neuroendocrine and neurochemical responses to novelty stress in young and old male F344 rats: effects of d-fenfluramine treatment

To understand some of the mechanisms underlying the neuroendocrine and neurochemical changes associated with aging, we administered the serotonin [5-hydroxytryptamine (5-HT)] releaser and reuptake inhibitor d-fenfluramine (d-FEN; 0.0, 0.2, or 0.6 mg/kg/day, p.o) for 30-38 days to young (4 months) and old (22 months) F344 male rats. Rats were stressed by placement into a novel open field (OF) for 20 min before sacrifice. Control animals were sacrificed immediately upon removal from their home cage (HC). Old rats exhibited less (p < 0.05) exploratory behavior than young rats, which was not altered by treatment with d-FEN. Old HC rats also had higher (p < 0.05) basal plasma levels of adrenocorticotropic hormone (ACTH) and prolactin (PRL) than young HC rats. Old OF rats showed higher (p < 0.05) levels of ACTH and corticosterone (CORT) than young OF animals. A stress-induced increase in PRL secretion was not observed in old rats. Subchronic low-dose d-FEN normalized the enhanced ACTH and CORT responses of old animals to novelty. In addition to these endocrine changes, stress-induced increases in medial frontal cortex (MFC) dopamine (DA) and norepinephrine (NE) turnover also were observed. The increase in NE turnover was greater (p < 0.01) in old than in young rats. d-FEN treatment blocked the stress-induced increase in MFC NE but not MFC DA turnover in both young and old rats. These data support a role for 5-HT and/or NE in some age-related neuroendocrine perturbations and suggest that increased 5-HT neurotransmission can normalize the hyperactivation of the hypothalamo-pituitary-adrenal axis of old male rats.

Perioperative platelet reactivity and the effects of clonidine

BACKGROUND

Increased postoperative platelet reactivity may contribute to arterial thrombotic complications following surgery. alpha 2 Agonists, which are being used increasingly to blunt the stress response of surgery, increase platelet aggregation in vitro. We compared perioperative changes in platelet reactivity in 21 patients receiving either clonidine or placebo.

METHODS

Patients undergoing major abdominal surgery were randomized to receive oral and transdermal clonidine (n = 11) or placebo (n = 10). All patients received similar perioperative management, including preoperative sedation, general anesthesia without neuraxial opioids, or local anesthetics and postoperative patient-controlled intravenous morphine. Blood was obtained for measurement of clonidine level, fibrinogen concentration, platelet count, and platelet reactivity (impedance aggregometry and dense granule release) before induction and 24, 48, and 72 h postoperatively.

RESULTS

Thirteen of the 21 patients had biopsy-proven cancer at surgery, 5 of 11 received clonidine and 8 of 10 received placebo (NS). Clonidine levels were therapeutic (1-2 ng/ml) throughout the study period. Clonidine administration had no effect on platelet count or platelet reactivity. Therefore, the groups were combined for further analysis. In this group (n = 21), compared to preoperative values, fibrinogen levels rose maximally (36%) at 72 h postoperatively and platelet counts decreased 22% at 48 h. Platelet reactivity (aggregation and degranulation) to collagen, adenosine diphosphate, arachidonic acid, and ristocetin, increased at 24, 48, and 72 h postoperatively. Thrombin-induced (supramaximal stimulus) dense granule release did not change from preoperative values.

CONCLUSIONS

These data indicate that major abdominal surgery causes increased platelet reactivity postoperatively but does not effect maximal degranulation. This increased platelet reactivity occurs within 48 h of surgery, coinciding with the peak incidence of postoperative arterial thrombotic complications. Clonidine administration has no effect on surgically induced changes in platelet reactivity. In this surgical patient population, the use of clonidine should not increase the risk of platelet-induced perioperative arterial thrombosis.