Immunization of mice with urease vaccine affords protection against Helicobacter pylori infection in the absence of antibodies and is mediated by MHC class II-restricted responses.

We examined the roles of cell- and antibody-mediated immunity in urease vaccine-induced protection against Helicobacter pylori infection. Normal and knockout mice deficient in major histocompatibility complex (MHC) class I, MHC class II, or B cell responses were mucosally immunized with urease plus Escherichia coli heat-labile enterotoxin (LT), or parenterally immunized with urease plus aluminum hydroxide or a glycolipid adjuvant, challenged with H. pylori strain X47-2AL, and H. pylori organisms and leukocyte infiltration in the gastric mucosa quantified. In an adjuvant/route study in normal mice, there was a direct correlation between the level of protection and the density of T cells recruited to the gastric mucosa. In knockout studies, oral immunization with urease plus LT protected MHC class I knockout mice [beta2-microglobulin (-/-)] but not MHC class II knockout mice [I-Ab (-/-)]. In B cell knockout mice [microMT (-/-)], vaccine-induced protection was equivalent to that observed in immunized wild-type (+/+) mice; no IgA+ cells were detected in the stomach, but levels of CD4(+) cells equivalent to those in the wild-type strain (+/+) were seen. These studies indicate that protection of mice against H. pylori infection by immunization with the urease antigen is dependent on MHC class II-restricted, cell-mediated mechanisms, and antibody responses to urease are not required for protection.

Pertussis toxin blocks the somatostatin-induced inhibition of growth hormone release and adenosine 3',5'-monophosphate accumulation.

A protein toxin synthesized by the bacterium Bordetella pertussis has the unique property of blocking a number of receptor-mediated inhibitory systems which are linked to adenylate cyclase. We found that pertussis toxin (PT) eliminates the ability of somatostatin to reduce both basal and GH-releasing factor-stimulated GH release in primary cultures of rat pituitary cells. Furthermore, the ability of somatostatin to reduce GH-releasing factor-induced cAMP accumulation in the cells is significantly attenuated after PT treatment. The PT effect, which is dose dependent and prevented by pretreatment with anti-PT antibodies, represents an alteration in somatostatin efficacy rather than potency. The modification of somatostatin responsiveness persists for at least 5 days after toxin removal. The PT actions on the somatotroph are similar to the effects on other eukaryotic cell types. The combination of available data indicates that the toxin acts on a highly conserved component(s) that is obligatory for transducing the inhibitory hormone message into the cell.

Paradoxic pupillary constriction in a patient with congenital stationary night blindness.

Paradoxic pupillary constriction to an "off-step" of light was studied in a 35-year-old woman with congenital stationary night blindness. ERG was of the Schubert-Bornschein type (scotopic B-wave absent); fundi were normal for a high myope. Paradoxic constrictions were larger in response to full field and peripheral off-steps from low photopic levels than from higher photopic levels. The patient's "on response" was smaller in magnitude and slower in both latency and dynamics than the on-response of normal subjects. Pupillary hippus was larger in magnitude and more peaked in the patient than in normal subjects. Steady-state (tonic) pupil size increased paradoxically with increased light level over the range 1-2 log fL.

Clinical, hemodynamic and sympathetic neural correlates of heart rate variability in congestive heart failure.

Heart rate (HR) variability has long been recognized as a sign of cardiac health. In the presence of heart disease, HR variability decreases, an observation that has been associated with poor prognosis in a number of recent studies. HR variability is particularly altered in congestive heart failure (CHF), a condition associated with a number of typical functional hemodynamic and neurohumoral alterations. The relation of measurements of HR variability to these abnormalities in patients with heart failure has not been carefully examined. Twenty-three patients (19 men, 4 women, mean age 49 years) with New York Heart Association class II to IV CHF were studied prospectively without cardiac medications; radionuclide ventriculography, right-sided heart catheterization, peroneal microneurography, plasma norepinephrine and 24- to 48-hour ambulatory electrocardiography were performed. Average RR interval and its standard deviation, and HR power spectrum (0 to 0.5, 0.05 to 0.15 and 0.2 to 0.5 Hz) were derived from the ambulatory electrocardiographic recordings and compared with left ventricular ejection fraction, thermodilution cardiac output, pulmonary arterial wedge pressure, New York Heart Association class, age, muscle sympathetic nerve activity (peroneal nerve) and norepinephrine level by linear regression. None of the measures of HR variability were significantly related to age, left ventricular ejection fraction, cardiac output or functional classification, whereas the 0.05 to 0.15 and 0.20 to 0.50 Hz components were weakly but significantly related to cardiac output (r = 0.49 and 0.42, p = 0.02 and 0.045, respectively). In contrast, a generally stronger and negative relation was demonstrated between spectral and nonspectral measurements of HR variability, and indicators of sympathoexcitation, muscle sympathetic nerve activity and plasma norepinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pentafraction and hetastarch plasma expansion on lung and soft tissue transvascular fluid filtration.

BACKGROUND: Hetastarch and pentafraction are high molecular weight starch solutions designed to augment plasma oncotic pressure. Although clinical utilization of hetastarch has been limited by reported coagulation abnormalities, pentafraction is a newer derivative that appears to have few adverse hemostatic effects. We examined the ability of pentafraction to modulate lung and soft tissue transvascular fluid filtration under hypoproteinemic conditions compared with hetastarch and Ringer's lactate (LR). METHODS: Awake, protein-depleted sheep (n = 19) were prepared with lung and soft tissue lymph fistulas, and comparable infusions of 5% pentafraction (n = 6), 6% hetastarch (n = 6), or LR (n = 7) were administered. Plasma and lymph samples were collected during 24-hour period to determine changes in protein concentrations, plasma-to-lymph oncotic gradients, and lung (QL) and soft tissue (QS) lymph flows. RESULTS: QL and QS rose nearly twofold after protein depletion alone. LR infusion increased QL and QS to 8.7 +/- 1.7 and 3.1 +/- 0.6 times normoproteinemic baseline, respectively (p < 0.05). In contrast, hetastarch and pentafraction infusion limited the increase in QL to 4.2 +/- 1.1 and 4.0 +/- 0.8 times normoproteinemic baseline, respectively (p < 0.05 versus LR) and did not significantly increase QS. Hetastarch and pentafraction infusions increase plasma oncotic pressure by nearly 6 mm Hg, which significantly widened the plasma-to-lymph oncotic pressure gradients above preinfusion baseline by 4.7 +/- 0.7 and 3.4 +/- 0.4 mm Hg in lung and 4.6 +/- 0.7 and 3.2 +/- 0.4 mm Hg in soft tissue, respectively (p < 0.05). CONCLUSIONS: Both hetastarch and pentafraction limit transvascular fluid filtration under hypoproteinemic conditions by augmenting plasma oncotic pressure and the plasma-to-lymph oncotic pressure gradient. Because of fewer adverse hemostatic effects pentafraction may be an improvement over current therapies in critical care fluid management.

Management of paraesophageal hernia with a selective approach to antireflux surgery.

BACKGROUND: The role of an antireflux procedure in the management of paraesophageal hernia is controversial. To address this issue, we reviewed our experience with selective use of antireflux procedures in patients with pure paraesophageal hernia (type II; n = 26) and those with a partial sliding component (type III; n = 11). PATIENTS AND METHODS: Surgical repair was performed on diagnosis in all 37 patients. Competency of the lower esophageal sphincter was evaluated on the basis of reflux symptoms, and objectively, with endoscopy in 21 patients and 24-hour esophageal pH studies in 17 patients. Repair included an antireflux procedure in 11 patients, as indicated by reflux disease. RESULTS: Preoperatively, 80% of both type II and type III patients reported obstructive symptoms. Reflux symptoms were present in 27% of patients--19% of type II and 45% of type III patients. Endoscopy revealed esophagitis in 5 cases, and 24-hour pH studies indicated significant reflux in 3 of 17 patients. There were no operative deaths and 1 recurrence. Symptoms improved in 92% of patients after surgery. Medically manageable reflux was identified in 2 patients. CONCLUSIONS: Frequent obstructive symptoms and the potential for gastric volvulus indicate elective repair of paraesophageal hernia on diagnosis. Significant gastroesophageal reflux is less common, especially in type II patients, and excellent symptomatic results are obtained with selective application of an antireflux procedure.

Unidirectional block in cardiac fibers: effects of discontinuities in coupling resistance and spatial changes in resting membrane potential in a computer simulation study.

The mechanisms for conduction and unidirectional block (UDB) in cardiac tissue under spatial changes in cell-to-cell coupling resistivity (Ri) and resting potential (Vrest) were studied. Cable theory was used to simulate the cardiac fiber, and the Beeler and Reuter model, or a modified model based on the Ebihara-Johnson formulation was used to describe the ionic currents. The effects of discontinuities in Ri as would result from collagenous or fibrotic tissue on propagation characteristics were studied. We were especially interested in the effects on propagation characteristics of discontinuities in Ri in the border zone between normal and ischemic tissue. We found that conduction block is more likely to occur when an abrupt decrease in Ri is encountered as compared to an abrupt increase in Ri. Discontinuities in Ri were found to cause changes in propagation characteristics, changing regions of bidirectional block to UDB or bidirectional propagation. Spatial changes in Vrest were also studied. We found that when Vrest alone was altered, block was not likely to occur, while discontinuities in Ri superimposed with Vrest gradients increased the likelihood of block. We also found that Ri discontinuities located in the border zone between normal and ischemic tissue can create exit block or propagation of a parasystolic focus.

Level dependent signal flow in the light pupil reflex. I. Latency of time domain responses to transient stimuli.

Latency of pupillary responses to light stimuli are smaller for larger steps of light, and larger for smaller steps of light (Alpern 1954; Lowenstein et al. 1964; Lee et al. 1969; Terdiman et al. 1969; Cibis et al. 1977; and many others). Miller and Thompson (1978), however, reported negligible change in pupil cycle time (period of high gain instability oscillations) with increased mean brightness. Sandberg and Stark (1968) reported a negligible reduction in phase lag of pupillary responses to sinusoidal light stimuli as the modulation coefficient (m) increased. To resolve the inconsistency between the well-documented dependence of latency upon brightness, and the apparent absence of level dependence in the phase characteristics (as reflected directly in the responses to sinusoidal stimuli and indirectly in pupil cycle time experiments) we measured: 1. Latency to step stimuli of light, 2. Phase of responses to sinusoidal light stimuli and 3. Period (pupil cycle time) of high gain instability oscillations. The dependence of pupillary latency upon stimulus level (both light and accommodation) and the interaction between accommodation and light responses were investigated. We show that most of the level dependence of light-pupil latency resides in the afferent path. In the companion papers, we demonstrate that: 1. Phase of pupillary response to sinusoidal light stimuli is reduced by increased mean light level, but is independent of pupil size and accommodative stimulus level; and 2. The period of high gain oscillations is shown to decrease with increased mean light level.(ABSTRACT TRUNCATED AT 250 WORDS)

Level dependent signal flow in the light pupil reflex. III. Phase velocity in high gain instability oscillations.

The pupil can be excited to sustained oscillations under high gain feedback conditions. The period of these oscillations (cycle time) is reduced by increased average light level by an amount commensurate with reductions in phase lag reported in the companion paper (Myers et al. 1991b). A mathematical model of this phenomenon is used to unify and clarify experimental data presented here and in the literature.

Identification of multifiber neural spike trains by interval prediction and morphology.

Interpretation of neurograms from multifiber preparations is usually limited to forming a grand running average. In so doing, individual nerve activity is lost. This information is important in studying nervous system activity. We have developed a method to find the rates of constituent nerve fibers using linear one-step prediction and cross correlation between the spike template and instantaneous spikes. Some size discrimination is employed, as is a memory to mark spikes which are "accounted for." Thus we are able to parse out the several rates which make up an aggregate spike train. Our results show that some afferent baroreceptor fibers may increase rate, while others may decrease rate, in response to holding carotid sinus pressure at a high level for 10 minutes.

Topology of the near response triad.

The near response complex comprises three elements: accommodation, convergence, and pupillary constriction. The synkinesis between vergence and accommodation is well understood functionally, if not neuroanatomically. The latencies of near response components were measured in four healthy, experienced subjects to determine how the pupillary component is mediated. Addition of disparity stimulus to blur, yielding a near stimulus, reduces the latency of vergence eye movements and of accommodation by an amount that is significantly greater than the corresponding reduction in pupil latency. None of the existing hypotheses: vergence-pupil, accommodation-pupil or symmetric dual interaction, can account for this difference. Therefore, we present a new hypothesis: asymmetric dual interaction between accommodation and vergence.

Level dependent signal flow in the light pupil reflex. II. Phase velocity of responses to sinusoidal light stimuli.

Pupillary responses to sinusoidal light stimuli were measured over a range of light levels and frequencies. The phase lag and equivalent time delay of these responses were reduced in an approximately log-linear fashion with increasing mean light level (slope = -60 ms/log unit). The magnitude of this level dependence is reduced at higher frequencies, and at higher light levels. This nonlinear level dependent signal flow (LDSF) effect is shown to be essentially independent of target distance (accommodative stimulus) which influences pupil size, and of pupil size itself. Thus most of the level dependence probably resides in the afferent path of the light-pupil reflex arc, before the accommodation signal joins the light signal in the Edinger-West-phal nucleus. A systems model is presented to the LDSF effect described here and in the companion papers (Myers and Stark 1993a, b). When parameters of the model are adjusted to fit pupillary responses to transient light stimuli over a range of light levels, the model simulates reduced phase lag in response to increased mean light level, and the reduction in this LDSF effect with increased mean light level or increasing stimulus frequency without further changes in parameters. This latter reduction explains the relatively small level dependence seen in latency data (-34 ms/log unit). These data will be shown (Myers and Stark 1990b) to be commensurate with reduction in pupil cycle time (increased frequency of oscillation) observed in high gain oscillation experiments as mean brightness increases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptive realtime compensatory feedback to open the light-pupil reflex loop.

Integrity of the visual pathway is often clinically determined from response of the pupil to light. The need for more quantitative measurement of pupillary response has led engineers to investigate the light-pupil reflex with systems analysis techniques. The results have made the light-pupil reflex a model of the application of the principles of control theory to physiologic mechanisms. This analysis required that the system be rendered open loop by focusing the stimulus at the center of the pupil. Patients may not be able to restrict their head and eye movement well enough to permit the feedback loop to be rendered open loop optically. Thus, clinical applications of the technique have been limited. A means of opening the feedback loop by using a realtime deterministic autoregressive moving average prediction algorithm integrated into a computer based television pupillometer has been developed. It employs a model reference adaptive scheme to identify the physiologic system, then predicts future values of pupil area to compensate for delays in the measuring apparatus. A computer driven liquid crystal display shutter controls retinal illuminance to render the light-pupil reflex open loop. This technique reduced the mean square error of retinal illuminance by about 75% compared to uncompensated pupil responses.

Susceptibility of Bordetella species to growth inhibition and killing by chlorpromazine.

Chlorpromazine, the prototype phenothiazine tranquilizer, inhibited the growth and killed organisms of the genus Bordetella. There were striking differences, however, among the three Bordetella species. Bordetella pertussis was most susceptible, with some inhibition of growth at greater than or equal to 4 micrograms/ml and killing at 16 micrograms of chlorpromazine per ml. Bordetella parapertussis and Bordetella bronchiseptica were less susceptible, with killing at 32 and 256 micrograms/ml, respectively. Although the phenothiazines were inhibitory for Bordetella extracytoplasmic adenylate cyclase, the lethal effect occurred at a lower concentration and did not appear to involve modification of the enzyme activity. Exposure of B. pertussis to combinations of chlorpromazine and erythromycin resulted in impaired growth at concentrations lower than that of either drug alone, but there was no evidence that the two drugs interacted either synergistically or antagonistically.

Pneumocystis carinii pneumonia postrestorative proctocolectomy for ulcerative colitis: a role for perioperative prophylaxis in the cyclosporine era? Report of a case and review of the literature.

PURPOSE: Medical management of severe ulcerative colitis has used cyclosporine with increasing frequency as an adjuvant to systemic steroids and mercaptopurine. However, the effects of combined management with cyclosporine and prednisone may lead to significant immune compromise and adversely affect operative morbidity in the event urgent surgery is required. METHODS: A case is reported of a 43-year-old white male who presented with severe ulcerative colitis. The patient had been initially treated with prednisone and cyclosporine for six weeks before surgical intervention. The intractability of his ulcerative colitis caused the patient to present to surgery, where he underwent restorative proctocolectomy. RESULTS: On initial presentation, the patient manifested systemic signs of severe ulcerative colitis with hypoalbuminemia, anemia, and weight loss, despite continuous prednisone and cyclosporine management. Before surgical intervention, a chest x-ray and the patient's respiratory status were normal. A total abdominal colectomy with ileal pouch reconstruction and temporary loop ileostomy were performed without incident. On the fifth postoperative day, the patient developed respiratory failure, which was subsequently diagnosed as Pneumocystis carinii pneumonia. Although ventilator support and both aggressive medical and surgical management eventually resulted in successful outcome, significant perioperative morbidity occurred. CONCLUSIONS: In the era of aggressive medical management for ulcerative colitis with both steroids and cyclosporine, the complications of immunosuppression may be significant, including opportunistic pneumonia. Prophylaxis against P. carinii pneumonia with sulfa antibiotics should be considered, especially in patients for whom proctocolectomy is a potential end point.

Spectral analysis of arterial pressure lability in rats with sinoaortic deafferentation.

Traditionally, the standard deviation (SD) of the mean arterial pressure (AP) has been used as an index for the AP lability produced by interruption of baroreceptor afferents. Although a useful measure of variance about the mean, the SD does not provide any information about the temporal characteristics of this variability. We employed two different spectral analytic techniques to characterize AP waveforms in rats with sinoaortic deafferentation (SAD) and in sham-operated (Sham) rats to determine if the AP waveform in SAD animals was qualitatively and/or quantitatively different from that of Sham animals. The SAD and Sham animals exhibited qualitatively different spectral profiles, suggesting that lability of AP in SAD animals is not simply an exaggeration of normal fluctuations. In addition, a low-frequency (0.3-0.5 Hz) spectral peak was found in Sham but not SAD animals, suggesting that it is associated with the baroreflex. Finally, we observed in both normal rats and rats without intact baroreceptors that the spectral components of AP are not static but rather vary continuously across time.

Pulmonary vascular filtration of starch-based macromolecules: effects on lung fluid balance.

BACKGROUND: Pulmonary edema is a complication of critical care fluid management that may be restricted by the use of oncotically effective resuscitation fluids. Potentially beneficial oncotic properties of starch-based plasma volume expanders such as hetastarch (Het), pentafraction (Pen), and Dextran-70 (Dex) may be compromised by their broad range of molecular masses, some of which are small enough to filter from the circulation. Leakage of these molecules into the pulmonary interstitium may limit their oncotic effectiveness and enhance fluid filtration. We measured the filtration of these three resuscitation solutions into lung lymph to evaluate their oncotic contribution to pulmonary edema formation. MATERIALS AND METHODS: Unanesthetized euvolemic adult sheep, prepared with chronic lung lymph fistulae, underwent plasma volume expansion with Het (n = 6), Pen (n = 6), or Dex (n = 6 ) (6%, 35 ml/kg/90 min). Oncotic effectiveness was determined by measuring plasma and lymph oncotic pressures and the oncotic pressures contributed by each starch. Pulmonary hydrostatic pressures and lung lymph flows (Q(L)) were also measured. Results are expressed as means +/- SEM. Comparisons were made by two-factor analysis of variance. RESULTS: Dex contributed 9.0 +/- 0.9 mmHg to the plasma oncotic pressure, significantly more than Het and Pen (5.3 +/- 0.6, 6.5 +/- 0.6 mmHg, respectively). However, Dex filtration also contributed 6.1 +/- 0.5 mmHg to the lymph oncotic pressure, compared to 3.1 +/- 0.3 and 4.7 +/- 0.5 mmHg for Het and Pen, respectively (P < or = 0.05). Dex, Het, and Pen raised Q(L) over baseline by 7.7 +/- 1.5, 4.3 +/- 1.0, and 3.2 +/- 0.7 ml/30 min, respectively (P < or = 0.05). Dex increased Q(L) significantly more than Het or Pen. CONCLUSIONS: Pen and Het demonstrated greater oncotic effectiveness because of restricted plasma-to-lymph macromolecular filtration and limited transvascular fluid flux. By comparison, Dex filtered rapidly and increased transvascular fluid filtration. Pen appears to possess filtration properties that optimize critical care fluid management compared to currently available colloid solutions such as Het and Dex.

Tn5-induced mutations affecting virulence factors of Bordetella pertussis.

Transposon Tn5 was used to isolate mutants of Bordetella pertussis. Strains with Tn5 insertions were screened for loss of virulence-associated factors, including filamentous hemagglutinin, hemolysin, and pertussis toxin. Several mutants deficient for hemolysin production were obtained. All produced dermonecrotic toxin, pertussis toxin, and filamentous hemagglutinin, but were found to vary with respect to adenylate cyclase production. One hemolysin mutant had no detectable adenylate cyclase activity; others had 0.6% or 16% wild-type activity, whereas a fourth seemed to be unaffected in terms of adenylate cyclase activity. Mutants deficient in the ability to hemagglutinate sheep erythrocytes were also isolated. These mutants either failed to synthesize or produced reduced amounts of three protein species of 200,000, 130,000, and 100,000 daltons, all of which reacted with antiserum to filamentous hemagglutinin. Pertussis toxin mutants were identified by screening culture supernatants for failure to induce a clustered growth pattern in Chinese hamster ovary cells, and identification was confirmed by the standard histamine-sensitizing assay in mice. These mutants will be useful to determine the relative contribution of each virulence factor to pathogenicity as well as to determine the identity of the antigens important in protective immunity.