Decision making about prophylactic oophorectomy among at-risk women: psychological influences and implications

OBJECTIVE

Women with a family history of ovarian cancer are confronted with difficult decisions regarding the management of their risk status. Currently, the main preventive option available is prophylactic oophorectomy. The objective of the present paper is to review research and theory on psychological factors that influence decision making about preventive surgery and discuss the implications for patient management.

METHODS

Guided by a cognitive-social framework, the literature on decision making about preventive surgery is reviewed and integrated.

RESULTS

The available studies show that women are more likely to opt for surgery if they feel more vulnerable to cancer, believe that surgery will prevent cancer, and are worried about developing cancer. Further, the response to ovarian risk is influenced by the individual's characteristic psychological style: monitors (who typically scan for and amplify threatening cues) tend to feel more vulnerable to cancer and more distressed about their cancer risk than blunters (who typically distract from threatening cues) do.

CONCLUSION

On the basis of prior research, monitors may be more likely to choose surgical intervention to reduce their distress, without fully anticipating the psychological and medical consequences of that decision. In order to facilitate informed decision making, counseling protocols should be designed to enable the patient to understand and take account of the psychological consequences of the available medical options. Future studies are needed to systematically extend and explore the proposed theory-based relationships.

Emergence of FY*A(null) in a Plasmodium vivax-endemic region of Papua New Guinea

In Papua New Guinea (PNG), numerous blood group polymorphisms and hemoglobinopathies characterize the human population. Human genetic polymorphisms of this nature are common in malarious regions, and all four human malaria parasites are holoendemic below 1500 meters in PNG. At this elevation, a prominent condition characterizing Melanesians is alpha(+)-thalassemia. Interestingly, recent epidemiological surveys have demonstrated that alpha(+)-thalassemia is associated with increased susceptibility to uncomplicated malaria among young children. It is further proposed that alpha(+)-thalassemia may facilitate so-called "benign" Plasmodium vivax infection to act later in life as a "natural vaccine" against severe Plasmodium falciparum malaria. Here, in a P. vivax-endemic region of PNG where the resident Abelam-speaking population is characterized by a frequency of alpha(+)-thalassemia >/=0.98, we have discovered the mutation responsible for erythrocyte Duffy antigen-negativity (Fy[a-b-]) on the FY*A allele. In this study population there were 23 heterozygous and no homozygous individuals bearing this new allele (allele frequency, 23/1062 = 0.022). Flow cytometric analysis illustrated a 2-fold difference in erythroid-specific Fy-antigen expression between heterozygous (FY*A/FY*A(null)) and homozygous (FY*A/FY*A) individuals, suggesting a gene-dosage effect. In further comparisons, we observed a higher prevalence of P. vivax infection in FY*A/FY*A (83/508 = 0.163) compared with FY*A/FY*A(null) (2/23 = 0.087) individuals (odds ratio = 2.05, 95% confidence interval = 0.47-8.91). Emergence of FY*A(null) in this population suggests that P. vivax is involved in selection of this erythroid polymorphism. This mutation would ultimately compromise alpha(+)-thalassemia/P. vivax-mediated protection against severe P. falciparum malaria.

Specific worry about breast cancer predicts mammography use in women at risk for breast and ovarian cancer

This longitudinal study examined predictors of mammography use among women with a family history of breast cancer participating in a risk assessment and surveillance program (N = 213). Assessed were background variables (age, prior mammography utilization), cognitive variables (perceived vulnerability), and affective variables (cancer worry and general distress). Results of logistic regression analyses predicting adherence 1 year after baseline contact, in which variables of prior utilization, feelings of vulnerability, and general distress were controlled for, indicated that cancer worry and age were significant predictors of mammography adherence. Results suggest that moderate levels of cancer worry facilitate, rather than undermine, adherence. The results have implications for the construction of educational messages that should be designed to acknowledge feelings of cancer-specific worry and to provide guidance in health protective behaviors.

Association between subjective sleep quality and depression on immunocompetence in low-income women at risk for cervical cancer

OBJECTIVE

The purpose of this study was to investigate whether subjective sleep quality is more strongly associated with immunocompetence than depression among women at risk for cervical cancer.

METHODS

Participants were 91 women referred for colposcopy because of abnormal results on a Pap smear. On the day of the procedure. participants completed the Center for Epidemiological Studies Depression Scale, two indices of subjective sleep quality (ie, satisfaction with sleep obtained and degree of sleep restfulness), and a health behaviors assessment questionnaire. Levels of peripheral blood lymphocyte subpopulations (helper T, cytotoxic/suppressor T, NK, and B cells) were also assessed at this time. Approximately 10 days later, the presence of depressive disorder was assessed using the Structured Clinical Interview for DSM-III-R.

RESULTS

Hierarchical regression analyses revealed that satisfaction with the amount of sleep obtained was significantly associated with the circulating number and percentage of helper T cells (T(H)/CD4+) and the percentage of cytotoxic/suppressor T cells (T(C)/CD8+), after controlling for confounder variables (ie, age, smoking status, and drug use). Depression was significantly associated only with the percentage of T(C) cells. Sleep satisfaction remained significantly associated with the number and percentage of T(H) cells and percentage of T(C) cells after controlling for the variance explained by depression.

CONCLUSIONS

Results of this study suggest that subjective sleep quality shares a significant and independent portion of the variance with immunity that is not accounted for by depression. Although the long-term impact of these immune alterations on disease progression needs to be directly explored, it may be important to systematically screen for and manage sleep disturbance in women at high risk for cervical cancer.

Complement-mediated lesion of sympathetic ganglia in vitro with acetylcholinesterase antibodies

When administered to rats, antibodies against acetylcholinesterase (AChE) selectively destroy presynaptic inputs to sympathetic ganglia. To investigate the mechanism of this immunolesion, we created an in vitro system in which relevant components could be manipulated. Freshly dissected rat superior cervical ganglia (SCG) were incubated 15-20 h at 37 degrees C in fresh human serum (a potent source of complement) with continuous oxygenation. More than 96% of neurons in six control ganglia retained synaptic inputs, as defined by action potentials or excitatory postsynaptic potentials (EPSP) upon stimulation of the preganglionic trunk. However, when anti-AChE antibodies were present (0.16 mg/ml), none of 61 neurons from six incubated ganglia showed synaptic responses although membrane potential and input resistance remained normal. Staining for AChE and synaptophysin (a synaptic vesicle marker) was also disrupted in ganglia exposed to AChE antibodies in complement-sufficient serum. When complement was eliminated by substituting serum that was heat-inactivated or deficient in C3, synaptic input was retained in 60-90% of neurons incubated with AChE antibodies. Choline acetyltransferase activity (ChAT), an enzymatic marker of cholinergic cytoplasm in sympathetic ganglia, was largely lost after incubation with AChE antibodies and serum. However, incubation with AChE antibodies in heat-inactivated serum, or serum that was deficient in C3 or C8, caused no measurable loss of ganglionic ChAT activity. These findings strongly implicate the complement cascade in the destruction of preganglionic sympathetic terminals that follows binding of AChE antibodies.

No metal cofactor in orotidine 5'-monophosphate decarboxylase

Orotidine 5'-monophosphate decarboxylase (OMP decarboxylase, ODCase) is an important enzyme that catalyzes the final step of de novo pyrimidine nucleotide biosynthesis. The mechanism of this unique enzyme and whether metal ions play any role in catalysis have been topics of intense research interest. In this report, the role of Zn in ODCase was reexamined. Atomic absorption (AA) and X-ray absorption (XAS) spectroscopic studies did not detect zinc in active enzyme samples at high concentration. The XAS results also indicated the absence of other transition metal ions in ODCase.

Investigation of the kinetic mechanism of cytidine 5'-monophosphate N-acetylneuraminic acid synthetase from Haemophilus ducreyi with new insights on rate-limiting steps from product inhibition analysis

The presence of sialic acid as a component of cell surface lipooligosaccharides or capsular polysaccharides has been shown to be correlated with the virulence of a number of Gram-negative mucosal pathogens, including several Haemophilus and Neisseria spp. As part of our efforts to evaluate the role of sialic acid in the pathobiology of these organisms, we have initiated studies of the enzymes from Haemophilus ducreyi (the infectious agent of chancroid) responsible for the activation and attachment of sialic acid to the lipooligosaccharide. In this report, we describe results of an investigation of the steady-state kinetic mechanism of the activating enzyme, cytidine 5'-monophosphate N-acetylneuraminic acid (CMP-NeuAc) synthetase. Using a combination of initial velocity, product inhibition, and dead-end inhibition studies, the reaction is shown to be freely reversible and to proceed through an ordered bi-bi kinetic mechanism in which CTP binds first and CMP-NeuAc dissociates last. In addition, a detailed analysis of the kinetic expressions for the observable constants is presented showing how the variation in apparent product inhibition constants (Kii) can be used to predict the rate-limiting step in kcat, which appears to be dissociation of CMP-NeuAc in this enzyme. To our knowledge, this relationship has not been previously recognized.

[Reconstructive surgery of the efferent urinary tract in pelvic exenteration of gynecological tumors]

In locally advanced or recurrent tumors of the female genital tract anterior or total exenteration may be mandatory in case of tumor invasion into the lower urinary tract or if a second course of radiation therapy is not feasible. The management of resection and reconstruction of the affected lower urinary tract has to be well integrated into the gynecological therapeutic concept. In 11/32 patients the reconstruction of the partially resected lower urinary tract was feasible with preservation of a functionally intact urinary bladder. Urinary diversion following pelvic exenteration was achieved in 13/17 patients with a continent urinary reservoir and in 4/17 patients with an ileal conduit. Operative reinterventions were needed only in patients with continent urinary diversion in 5 cases. All these patients had a past history of primary radiation therapy of their gynecological tumor. In the remaining other 11 patients with a history of primary radiation therapy no complications occurred. 9 of 32 patients survived the operative procedure 40.8 (25-57) month with no evidence of recurrent tumor. Continent urinary diversion represents an excellent therapeutic option for replacement of function lost due to exenterative pelvic surgery. Stringent selection of patients is mandatory to consider the presented therapeutic concept a reasonable tool in the management of the described clinical situations.

Leptin receptor immunoreactivity in sympathetic prevertebral ganglion neurons of mouse and rat

Prevertebral ganglia, comprising the inferior mesenteric, superior mesenteric and celiac ganglia, contain the cell bodies of sympathetic neurons that regulate gastrointestinal motility, visceral blood flow, secretion and absorption. In the present study, we report the presence of leptin receptor-like immunoreactivity in the superior mesenteric and celiac ganglia of mice and rats. Ganglion neurons were immunopositive for leptin receptor. Confocal microscopy and three-dimensional (3-D) reconstruction of ganglion neurons filled with Lucifer yellow and then immunostained for leptin receptor showed that leptin receptor immunoreactivity was intracellular and that it was present on structures encircling the nucleus. These results raise the possibility that leptin may affect gastrointestinal function by acting on leptin receptors located in prevertebral ganglion neurons.

Alternative routes for entry of HgX2 into the active site of mercuric ion reductase depend on the nature of the X ligands

Wild-type mercuric ion reductase (CCCC enzyme) possesses four cysteines in each of its Hg(II) binding sites, a redox-active pair and a C-terminal pair. Mutation of the C-terminal cysteines to alanines (CCAA enzyme) leads to a loss of steady-state mercuric ion reductase activity using Hg(SR)2 substrates. However, CCCC and CCAA enzymes exhibit an equally high rate of binding and turnover using HgBr2 as substrate under pre-steady-state conditions [Engst and Miller (1998) Biochemistry 37, 11496-11507.]. Since the ligands in these HgX2 substrates differ both in size and in affinity for Hg(II), one or both of these properties may contribute to their different reactivities with CCAA enzyme. To further explore the importance of these two properties, we have examined the pre-steady-state reactions of CCCC and CCAA with Hg(CN)2, which has small, high-affinity ligands, and with Hg(Cys)2, which has bulky, high-affinity ligands. The results indicate that HgX2 substrates with small ligands can rapidly access the redox-active cysteines in the absence of the C-terminal cysteines, but those with large ligands require the C-terminal cysteines for rapid access. In addition, it is concluded that the C-terminal cysteines play a critical role in removing the high-affinity ligands before Hg(II) reaches the redox-active cysteines in the inner active site, since direct access of HgX2 substrates with high-affinity ligands leads to formation of an inhibited complex. Consistent with the results, both a narrow channel leading directly to the redox-active cysteines and a wider channel leading to the redox-active cysteines via initial contact with the C-terminal cysteines can be identified in the structure of the enzyme from Bacillus sp. RC607.

regA, a Volvox gene that plays a central role in germ-soma differentiation, encodes a novel regulatory protein

Volvox has two cell types: mortal somatic cells and immortal germ cells. Here we describe the transposon-tagging, cloning and characterization of regA, which plays a central role as a master regulatory gene in Volvox germ-soma differentiation by suppressing reproductive activities in somatic cells. The 12.5 kb regA transcription unit generates a 6,725 nucleotide mRNA that appears at the beginning of somatic cell differentiation, and that encodes a 111 kDa RegA protein that localizes to the nucleus, and has an unusual abundance of alanine, glutamine and proline. This is a compositional feature shared by functional domains of many ‘active’ repressors. These findings are consistent with the hypothesis that RegA acts in somatic cells to repress transcription of genes required for growth and reproduction, including 13 genes whose products are required for chloroplast biogenesis.

glsA, a Volvox gene required for asymmetric division and germ cell specification, encodes a chaperone-like protein

The gls genes of Volvox are required for the asymmetric divisions that set apart cells of the germ and somatic lineages during embryogenesis. Here we used transposon tagging to clone glsA, and then showed that it is expressed maximally in asymmetrically dividing embryos, and that it encodes a 748-amino acid protein with two potential protein-binding domains. Site-directed mutagenesis of one of these, the J domain (by which Hsp40-class chaperones bind to and activate specific Hsp70 partners) abolishes the capacity of glsA to rescue mutants. Based on this and other considerations, including the fact that the GlsA protein is associated with the mitotic spindle, we discuss how it might function, in conjunction with an Hsp70-type partner, to shift the division plane in asymmetrically dividing cells.

A 'sticky' interhemispheric switch in bipolar disorder?

Despite years of research into bipolar disorder (manic depression), its underlying pathophysiology remains elusive. It is widely acknowledged that the disorder is strongly heritable, but the genetics are complex with less than full concordance in monozygotic twins and at least four susceptibility loci identified. We propose that bipolar disorder is the result of a genetic propensity for slow interhemispheric switching mechanisms that become 'stuck' in one or the other state. Because slow switches are also 'sticky' when compared with fast switches, the clinical manifestations of bipolar disorder may be explained by hemispheric activation being 'stuck' on the left (mania) or on the right (depression). Support for this 'sticky' interhemispheric switching hypothesis stems from our recent observation that the rate of perceptual alternation in binocular rivalry is slow in euthymic subjects with bipolar disorder (n = 18, median = 0.27 Hz) compared with normal controls (n = 49, median = 0.60 Hz, p < 0.0005). We have presented evidence elsewhere that binocular rivalry is itself an interhemispheric switching phenomenon. The rivalry alternation rate (putative interhemispheric switch rate) is robust in a given individual, with a test-retest correlation of more than 0.8, making it suitable for genetic studies. The interhemispheric switch rate may provide a trait-dependent biological marker for bipolar disorder.

Patch-clamp recordings of membrane currents evoked during natural synaptic activity in sympathetic neurons

Membrane currents elicited by colonic distension and by electrical stimulation of the intermesenteric nerve containing colonic afferent nerve fibres were recorded from neurons of the mouse superior mesenteric ganglion at 20 degrees C with the whole-cell patch-clamp method. Electrically-evoked excitatory postsynaptic currents reversed at -3.5 mV. At membrane holding voltages of -70 mV and -110 mV, the excitatory postsynaptic currents were characterized by a single exponential decay with a mean (+/- S.E.M.) time-constant of 17.5 +/- 1.3 ms and 15.5 +/- 2.3 ms, respectively. Colonic distension evoked a series of the excitatory postsynaptic currents which ranged in amplitude from 10 to 700 pA (at a membrane holding voltage of -70 mV). Hexamethonium (100 microM) applied only to the ganglion abolished both electrically- and distension-evoked excitatory postsynaptic currents, suggesting activation of nicotinic acetylcholine receptors. The decay time-course of distension-evoked single excitatory postsynaptic currents was characterized by one, or, less commonly, by two exponentials. The decay time-constant histograms of distension-evoked single excitatory postsynaptic currents exhibited main kinetic components of 8.1 +/- 2.3 ms and 8.2 +/- 2.5 ms (peak +/- S.D.) at -70 and -110 mV membrane holding voltages, respectively. Longer time-constants ranging up to 51 ms were also observed. The number of the distension-evoked excitatory postsynaptic currents with a decay time-constant higher than 20 ms, as well as their mean amplitude, were significantly lower at -110 mV than at -70 mV membrane potential levels, in contrast to the currents with a decay time-constant lower than or equal to 20 ms. The results suggest that colonic afferent nerve fibres activate in the mouse superior mesenteric ganglion neurons a few populations of the postsynaptic nicotinic acetylcholine receptors with different channel kinetics, which are characterized by a lack of voltage sensitivity within -70 to -110 mV membrane potential range, except those with comparatively slow channel kinetics, which are possibly blocked by membrane hyperpolarization.

Binding and reactivity of Candida albicans estrogen binding protein with steroid and other substrates

In this report recombinant estrogen binding protein (EBP1), isolated originally from Candida albicans as a result of its high affinity for 17beta-estradiol, has been purified extensively using a modified affinity purification scheme originally developed for a homolog of EBP1, old yellow enzyme (OYE). It is shown that like OYE, the protein binds a variety of compounds with a phenolic structure, including 17beta-estradiol, and compounds with an alpha, beta-unsaturated keto or aldehyde structure. In addition, EBP1 exhibits an NADPH oxidoreductase activity, transferring electrons from NADPH to all alpha,beta-unsaturated ketones and aldehydes tested via the tightly bound FMN cofactor. Analysis of the steady-state kinetics of these reactions indicate a tetra uni ping-pong mechanism. Inhibition of the steady-state reaction by 17beta-estradiol gives a Ki = 10 +/- 2 nM, and indicates exclusive binding of this steroid to the enzyme in its oxidized state. In contrast, 19-nortestosterone binds to both oxidized and reduced forms of the enzyme with dissociation constants of 600 +/- 100 and 650 +/- 90 nM, respectively. EBP1 also catalyzes a disproportionation reaction with certain compounds, in which two molecules of a cylic alpha,beta-unsaturated ketone, including the steroid 19-nortestosterone, are individually aromatized and reduced to the corresponding saturated ketone. Despite the extensive similarity in sequence and enzymic activity, notable differences between EBP1 and the OYE family of proteins exist with regard to the binding behavior and reactivity with the two steroids tested here, estradiol and 19-nortestosterone.

Rapid reduction of Hg(II) by mercuric ion reductase does not require the conserved C-terminal cysteine pair using HgBr2 as the substrate

Conditions are described under which the nonphysiological substrate mercuric bromide (HgBr2) is rapidly turned over, both by the wild type (CCCC) and by an active site double mutant (CCAA) of mercuric reductase in which the C-terminal cysteines 557' and 558' are replaced by alanine and only the redox-active pair Cys135 and Cys140 are available for catalysis. A maximum rate of turnover kcatapp of approximately 18 s-1 (at 3 degreesC) for both enzymes is observed, and at high [HgBr2]/[enzyme] ratios, inhibition is found. The UV-vis spectral changes during turnover are closely similar in both enzymes, indicating that catalysis follows the same enzymatic mechanism. Single-turnover analysis of the mutant enzyme shows that after binding of HgBr2, two further rapid events ensue, followed by reduction of the metal ion (kobs approximately 23.5 s-1). It is shown that under multiple-turnover conditions, completion of the catalytic cycle must occur via an ordered mechanism where rapid binding of a new molecule of HgBr2 to EH2.NADP+ precedes exchange of the pyridine nucleotide. Binding of HgBr2 to the active site triple mutant C135A/C557A/C558A (ACAA) is ca. 100-fold slower compared to that of the CCAA mutant and results in no detectable turnover. It is concluded that in the reducible enzyme.Hg(II) complex, the metal ion is coordinated to Cys135 and Cys140 and that for efficient catalysis both residues are required. Furthermore, the data imply that binding to EH2.NADPH occurs via initial rate-limiting attack of Cys135, followed by reaction with Cys140.

The three-dimensional structure of myenteric neurons in the guinea-pig ileum

Myenteric neurons of the guinea-pig ileum were intracellularly filled with the fluorescent dye Lucifer Yellow, optically sectioned with a confocal microscope and volume reconstructed to recreate 3-D images of the cells. The resulting images provide information not evident from regular microscopy. The somata varied in cross-section from flat-oval to nearly circular, and their surface membranes were marked by invaginations and protrusions significantly increasing the surface area of the somatic membrane. The neurons could be divided into four morphological classes: Dogiel type I, Dogiel type II, filamentous, and intermediate. There was no clear correlation between cell class and the shape of the soma in cross-section. The dendritic processes of all the neurons studied extended in an orad-caudad or circumferential direction of the bowel wall. When the filled neurons were viewed edge-on, the spatial arrangement of the processes was confined to a plane that had a thickness less than the thickness of the parent soma. The broad, short dendrites of Dogiel type I neurons were oval or nearly circular in cross-section. Directly measured quantitative data were obtained for the volume and surface area of the somata and visible processes. The structural details reported herein are likely to have important implications regarding the functional properties of individual enteric ganglion neurons and circuits of enteric ganglion neurons.

Procedural considerations in the real-ear measurement of completely-in-the-canal instruments

Conventional procedures for measurement of the real-ear aided response (REAR) of hearing aids are performed by placing the probe tube 5 mm beyond the medial tip of the canal portion of the earmold or shell and within 5 mm of the tympanic membrane. Completely-in-the-canal (CIC) instruments insert more deeply into the ear canal, and thus may make adherence to conventional probe-microphone procedures impossible. The REAR was measured at several probe tube insertion depths, using two insertion methods: through a probe vent and alongside the CIC shell. Results indicated that conventional probe insertion depth is not necessary for CIC instruments and may place some clients at risk for discomfort due to contact of the probe tube with the tympanic membrane. Placement of the probe tube along-side the CIC shell rather than through a probe vent resulted in slit leak venting effects that were highly variable across subjects. A probe tube placement protocol for use with CIC instruments is suggested.

Visualization of interstitial cells of Cajal in the mouse colon by vital staining

Interstitial cells of Cajal (ICCs) are believed to be a major element in generating the spontaneous rhythm of the gastrointestinal tract. A prominent problem in the study of these cells has been the difficulty in observing them in intact tissues. We used the lipophilic dye DiI to stain ICCs in the submucosal-circular muscle border of freshly dissected mouse colon. The placement of small DiI crystals in this area resulted in the labeling of ICC-like cells. Two main morphological cell types, viz., bipolar and multipolar, were noted. Bipolar cells had two primary processes emerging from the poles of an elongated soma. The mean length of these processes was 78.7 microm. These cells constituted 42.3% of the sample (n=105). Multipolar cells (54.3% of total) had a less elongated soma and extended 3-6 main processes whose mean length was 56.3 microm. These processes showed no preferred direction. The length of the primary processes of bipolar cells was 40% greater than that of multipolar cells (P<0.02). Three cells (2.9%) had only one primary process. The DiI stain could be converted into a stable electron-opaque product. Electron-microscopic observations showed that these cells had the typical appearance of ICCs reported in previous studies. This staining method should be useful for physiological investigations of ICCs in gastrointestinal tissues.

Diabetes: targeting an old adversary

For the first time in almost 20 years, new recommendations on diagnosis, classification, and testing strategies for diabetes have been issued. For clinical labs, combatting this old enemy under the new guidelines will include expanded patient screening and closer monitoring. Learn about the high-risk groups in the U.S. population, the long-term effects of diabetes, and how changes in testing approaches can improve disease management and patient outcomes.

Bradycardia induced by intravascular versus direct stimulation of the vagus nerve

BACKGROUND

Electrical stimulation of the parasympathetic nervous system results in slowing of the heart. We sought to determine whether cardiac vagal efferent axons can be stimulated adequately to induce bradycardia without disturbing the integrity of the thorax.

METHODS

Cardiodepressor effects elicited by direct stimulation of a vagus nerve in anesthetized dogs and pigs were compared with those generated when the same nerve was stimulated indirectly through bipolar electrodes placed in the adjacent superior vena cava.

RESULTS

The heart rate of dogs decreased by about 80% when electrical stimuli were delivered to the right thoracic vagus at the level of the thoracic outlet through bipolar electrodes placed either in the adjacent superior vena cava (intravascular method) or directly on the nerve (direct method). Maximal responses were achieved with 10-V, 5-ms, and 20-Hz stimuli. In anesthetized pigs, similar bradycardia occurred when the right cervical vagus or the right cranial thoracic vagus was stimulated either directly or indirectly through the intravascular method. Atrial dysrhythmias occurred when the stimulating electrodes were placed by either method within 1 cm of the right atrium in both animal models.

CONCLUSIONS

Controlled bradycardia can be induced during operation without the risk of generating cardiac dysrhythmias using electrical stimuli (10 V, 5 ms, and 10 to 20 Hz) delivered to the right cervical vagus nerve or the right cranial thoracic vagus nerve through adjacent intravascular electrodes.

Distribution of heme oxygenase and effects of exogenous carbon monoxide in canine jejunum

Carbon monoxide (CO) has been postulated to be a messenger in the gastrointestinal tract. The aims of this study were to determine the distribution of heme oxygenase (HO), the source for endogenous CO in the canine jejunum, and to determine the effects of CO on jejunal circular smooth muscle cells. HO-2 isoform was present in a population of myenteric and submucosal neuronal cell bodies, in nerve fibers innervating the muscle layers, and in smooth muscle cells. HO-1 isozyme was not detected in the canine jejunum. Exogenous CO increased whole cell current by 285 +/- 86%, hyperpolarized the membrane potential by 8.5 +/- 2.9 mV, and increased guanosine 3',5'-cyclic monophosphate (cGMP) levels in smooth muscle cells. 8-Bromo-cGMP also increased the whole cell current. The data suggest that endogenous activity of HO-2 may be a source of CO in the canine jejunum and that exogenously applied CO can modulate intestinal smooth muscle electrical activity. It is therefore reasonable to suggest a role for endogenously produced CO as a messenger in the canine jejunum.

Heme oxygenase 2 is present in interstitial cell networks of the mouse small intestine

BACKGROUND & AIMS

The interstitial cell (IC) network may be of fundamental importance in regulating gastrointestinal motility. Intestinal smooth muscle cells are depolarized in the absence of ICs, and there are no spontaneous slow waves. The messenger molecules between IC network and smooth muscle are unknown. Exogenous administration of CO relaxes the opossum internal anal sphincter and the guinea pig ileum, and it modulates potassium current and membrane potential of circular smooth muscle cells of the human jejunum. The aim of this study was to determine whether heme oxygenase (HO)-1 and HO-2, enzymes that catalyze the production of CO, are present in the IC network of the mouse small intestine.

METHODS

Antibodies specific for c-Kit, HO-1, and HO-2 were used for immunohistochemistry. Confocal images were obtained and were volume rendered, and the images were converted into three-dimensional images.

RESULTS

HO-2-like but not HO-1-like immunoreactivity was found in IC networks associated with the myenteric plexus and the deep muscular plexus.

CONCLUSIONS

HO-2 but not HO-1 is present in the IC cell network of the mouse small intestine. The enzymatic activity of HO-2 will result in the endogenous production of CO in IC networks of the mouse small intestine.

The use of propofol as an induction agent for halothane and isoflurane anesthesia in dogs

Cardiovascular, pulmonary, and quantitative electroencephalographic parameters were assessed in 12 anesthetized dogs to determine the compatibility of the injectable anesthetic propofol with halothane and isoflurane. No cases of apnea were observed during induction of anesthesia. An adequate level of anesthesia was established in each protocol as judged by both the lack of response to mechanical noxious stimuli (i.e., tail clamping) and evidence of reduction in total amplitude of brain wave activity. The initial propofol-mediated decrease in arterial blood pressure continued during either halothane (52.4%) or isoflurane (38%) anesthesia without a simultaneous increase in heart rate. The results of this study suggest that propofol, in combination with inhalant agents, can be used effectively and safely for canine anesthesia in veterinary practice.

Selective disruption of neurotransmission by acetylcholinesterase antibodies in sympathetic ganglia examined with intracellular microelectrodes

Antibodies to acetylcholinesterase (AChE) induce adrenergic dysfunction in rats by selective, complement-mediated destruction of preganglionic sympathetic nerve terminals. To analyze this phenomenon at the neuronal level, monoclonal antibodies to AChE (1.6 mg) were injected via the tail vein, and superior cervical ganglia (SCG) or inferior mesenteric ganglia (IMG) were studied in vitro. In control SCG, all impaled neurons generated action potentials during direct injection of depolarizing current or indirect stimulation through the preganglionic nerve. Current injection remained effective in ganglia from treated rats, but preganglionic stimulation was greatly impaired: at 12 h and 3 d, less than 10% of the neurons responded, even to a maximal stimulus (150 V); at 9 d, only 25% responded. By contrast, in IMG, synaptic transmission was much less affected by antibody exposure: 60% or more of examined neurons responded to preganglionic stimulation. Differences in antibody access did not explain differing sensitivities of SCG and IMG since immunohistochemistry showed rapid accumulation of IgG deposits in both ganglia. These results are believed to reflect widespread but subtotal preganglionic sympathectomy by AChE antibodies. Current information indicates that paravertebral ganglia are all antibody-sensitive, but some prevertebral ganglia are resistant, suggesting immunochemical differences between them.