Deep Learning Segmentation of the Nucleus Basalis of Meynert on 3T MRI

BACKGROUND AND PURPOSE

The nucleus basalis of Meynert is a key subcortical structure that is important in arousal and cognition and has been explored as a deep brain stimulation target but is difficult to study due to its small size, variability among patients, and lack of contrast on 3T MR imaging. Thus, our goal was to establish and evaluate a deep learning network for automatic, accurate, and patient-specific segmentations with 3T MR imaging.

MATERIALS AND METHODS

Patient-specific segmentations can be produced manually; however, the nucleus basalis of Meynert is difficult to accurately segment on 3T MR imaging, with 7T being preferred. Thus, paired 3T and 7T MR imaging data sets of 21 healthy subjects were obtained. A test data set of 6 subjects was completely withheld. The nucleus was expertly segmented on 7T, providing accurate labels for the paired 3T MR imaging. An external data set of 14 patients with temporal lobe epilepsy was used to test the model on brains with neurologic disorders. A 3D-Unet convolutional neural network was constructed, and a 5-fold cross-validation was performed.

RESULTS

The novel segmentation model demonstrated significantly improved Dice coefficients over the standard probabilistic atlas for both healthy subjects (mean, 0.68 [SD, 0.10] versus 0.45 [SD, 0.11], P = .002, t test) and patients (0.64 [SD, 0.10] versus 0.37 [SD, 0.22], P < .001). Additionally, the model demonstrated significantly decreased centroid distance in patients (1.18 [SD, 0.43] mm, 3.09 [SD, 2.56] mm, P = .007).

CONCLUSIONS

We developed the first model, to our knowledge, for automatic and accurate patient-specific segmentation of the nucleus basalis of Meynert. This model may enable further study into the nucleus, impacting new treatments such as deep brain stimulation.

Antipyretic and antimalarial activities of Solenostemon monostachyus

CONTEXT

Solenostemon monostachyus P. Beauv (Lamiaceae) is an important herb used traditionally in the treatment of malaria, fever, and other diseases.

OBJECTIVES

Antiplasmodial and antipyretic activities of S. monostachyus aerial extract were evaluated to ascertain the folkloric claim of its antimalarial and antipyretic activities.

MATERIALS AND METHODS

The extract (75-225 mg/kg) and fractions (chloroform and aqueous; 150 mg/kg) of S. monostachyus were investigated for suppressive, prophylactic, and curative antiplasmodial activities against chloroquine-sensitive Plasmodium berghei infections in Swiss albino mice and for antipyretic activity against 2,4-dinitrophenol and yeast-induced pyrexia. Artesunate (5 mg/kg) and pyrimethamine (1.2 mg/kg) were used as positive controls for antiplasmodial models. Thin films made from tail blood of each mouse were used to assess the level of parasitaemia of the mice.

RESULTS

The extract/fractions progressively reduced parasitaemia induced by chloroquine sensitive P. berghei infection in prophylactic (28.48-71.72%), suppressive (12.52-72.47%), and curative (22.4-82.34%) models in mice. These reductions were statistically significant (p < 0.01-0.001). They also improved significantly (p < 0.01-0.001) the mean survival time (MST) from 12.26 to 25.63 d relative to control (11.36 d). The activities of extract/fractions were incomparable with that of the standard drugs used (artesunate and pyrimethamine). The extract exerted prominent inhibition of pyrexia on dinitrophenol (87.33-90.11%, 5 h) and yeast (56.22-65.33, 5 h) induced pyrexia. Inhibition was significant (p < 0.05-0.001) from 3 to 5 h post-administration of extract and in a dose-dependent fashion.

CONCLUSION

The plant may possess antiplasmodial and antipyretic effects which may in part be mediated through the chemical constituents of the plant.

Non-operative management of acute cholecystitis in the elderly

BACKGROUND

Although cholecystectomy is the standard therapy for acute cholecystitis (AC), operative morbidity in the elderly may be high owing to medical co-morbidities and decreased physiological reserve. Outcomes of AC in the elderly have not been fully defined with regard to operative and long-term non-operative management.

METHODS

Patients aged 65 years or over admitted to a tertiary care centre with a diagnosis of AC between January 2000 and December 2009 were reviewed retrospectively. Patient data, operative and postoperative details were obtained. To determine cholecystectomy rates in the non-operative group, medical records were reviewed, and patients and families were interviewed.

RESULTS

A total of 290 patients underwent cholecystectomy during the index admission, of whom 59 (20·3 per cent) required conversion to open operation. Fifty-eight of these patients experienced 98 complications, including acute respiratory failure (27), pneumonia (18), myocardial infarction (16) and sepsis (15). Some 185 patients had non-operative treatment, of whom 67 underwent percutaneous cholecystostomy. Forty-four patients subsequently had elective cholecystectomy, with a complication rate of 23 per cent. One hundred and twenty-six patients were discharged without a plan for cholecystectomy; the rate of recurrent AC was 4 per cent among the two-thirds of patients followed to within 15 months of death. No deaths or major complications occurred among those with recurrent AC.

CONCLUSION

Despite selection of the best elderly candidates for cholecystectomy, postoperative morbidity was significant. Medical management, with interval cholecystectomy only for recurrent AC, may be appropriate in selected patients.

Influence of maternal corticosterone treatment on incubation length of eggs laid by Japanese quail hens selected for divergent adrenocortical stress responsiveness

1. Previous studies have shown that more yolk corticosterone is found in the eggs of random bred Japanese quail hens implanted with corticosterone during egg formation; both unstressed and stressed quail hens selected for exaggerated (high stress) rather than reduced (low stress) plasma corticosterone response to brief restraint deposit more corticosterone into their egg yolks. The length of egg incubation is also known to be shorter in eggs laid by high than low stress hens. 2. Here we investigated the interactive effects of quail stress line (low vs. high stress) with maternal corticosterone treatment (empty implant controls vs. corticosterone-implants) during egg formation on length of egg incubation. 3. Mean (+/-SEM) length of egg incubation for high stress control eggs (3973 +/- 04 h) was similarly shorter (by about 4.5 h) than that found for low stress control eggs (3928 +/- 02 h). In addition, on average, the incubation length of eggs laid by corticosterone-implanted hens (3929 +/- 05 h) was nearly 3 h shorter than that found for eggs laid by control hens (3958 +/- 02 h) regardless of stress line. 4. Line x hen-implant treatment effects on mean (+/-SEM) length of egg incubation partitioned in rank order as follows: low stress control (3978 +/- 05 h) > low stress corticosterone-implant (3959 +/- 07 h) > high stress control (3938 +/- 03 h) > high stress corticosterone-implant (3912 +/- 04 h). 5. Our original contention that selection for exaggerated adrenocortical responsiveness is associated with a reduction in the length of egg incubation was supported. Because maternal stress-induced elevations of yolk B are known to occur, the present findings of further shortenings of the hatching times of eggs of corticosterone-treated hens of both stress lines are also important to the poultry industry because they warn producers that unless stress in hens during egg formation is minimised, abbreviated egg incubation periods may result beyond the effects that a hen's genetic predisposition to adrenocortical stress responsiveness has on the length of egg incubation.

Fear responses of offspring from divergent quail stress response line hens treated with corticosterone during egg formation

Increased fearfulness has been associated with adrenocortical activation. Maternal corticosterone (B) treatment increases egg B, and elevated B in ovo enhances chick avoidance of humans. Quail selected for exaggerated (high stress, HS) rather than reduced (low stress, LS) plasma B response to stress are more fearful, and more B is found in HS hen eggs. Thus, we used tonic immobility (TI) and hole-in-the-wall box (HWB) emergence tests to assess fear in chicks hatched from eggs of LS and HS hens implanted with B or no B (CON). The number of inductions required to attain TI, latency to first alert head movement, and duration of TI were determined in one study and the latency until first vocalization (LATVOC), numbers of vocalizations (VOCS), proportions of chicks vocalizing, and the latencies to head (HE) and full-body (FE) emergence from a HWB were assessed in another. The LS chicks required less inductions (P < 0.0005) and had shorter latency to first alert head movement (P < 0.02) than HS chicks, although the duration of TI was unaffected by any of the treatments. During the acclimation period of the HWB tests, more (proportions of chicks vocalizing; P < 0.0001) HS chicks alarm-called sooner (LATVOC; P < 0.0001) and more often (VOCS; P < 0.0001) than did LS chicks, and, although maternal implant treatment did not affect LATVOC, progeny of B-implanted hens showed a tendency toward less (P < 0.07) VOCS than the CON. Chicks hatched from eggs of B-implant mothers also took longer to achieve HE (P < 0.06) and FE (P < 0.05) from the HWB than did their CON counterparts. Stress line, implantation treatment, and their interaction did not alter HE or FE responses. The data suggest that quail stress line genome may or may not be affecting certain fear and alarm responses in chicks via the same mechanism(s) that underlies how elevating maternal B increases egg levels of B that in turn alters the fear behavior of progeny.

The Growth of Silver on an Ordered Alumina Surface

The growth of Ag on an ordered Al2O3 surface was studied by low energy ion scattering spectroscopy (LEIS), scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD). Three-dimensional (3D) growth of Ag clusters was observed with STM and LEIS, with the cluster size increasing with Ag coverage. The XPS core level binding energies and the Auger parameters indicate a weak interaction between the Ag clusters and the Al2O3 support. Final state effects are determined to be the primary contribution to the Ag core level binding energy shift. Nonzero order kinetics was observed for Ag desorption in TPD with the Ag sublimation energy decreasing with decreasing cluster size.

High versus low body condition in mares: interactions with responses to somatotropin, GnRH analog, and dexamethasone

Mares that had previously been fed to attain body condition scores (BCS) of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) were used to determine the interaction of BCS with the responses to 1) administration of equine somatotropin (eST) daily for 14 d beginning January 20 followed by administration of GnRH analog (GnRHa) daily for 21 d and 2) 4-d treatment with dexamethasone later in the spring when mares in low BCS had begun to ovulate. The majority of mares with high BCS continued to cycle throughout the winter, as evidenced by larger ovaries (P < 0.002), more corpora lutea (P < 0.05), greater progesterone concentrations during eST treatment (P < 0.04), and more (P < 0.05) large- and medium-sized follicles. Treatment with eST alone or in combination with GnRHa had no effect (P > 0.05) on ovarian activity or ovulation. Plasma leptin concentrations were greater (P < 0.002) in mares with high BCS; however, there was no effect (P > 0.10) of eST treatment. Plasma IGF-I concentrations were greater (P < 0.0001) in mares treated with eST compared with mares given vehicle, and mares with high BCS had greater IGF-I (P < 0.02) and LH concentrations (P < 0.02) than mares with low BCS. Plasma leptin concentrations in mares with high BCS were increased (P < 0.001) within 12 h of dexamethasone treatment; the leptin response (P < 0.001) in mares with low BCS was greatly reduced (P < 0.001) and transient. Glucose and insulin concentrations also increased (P < 0.0001) after dexamethasone treatment in both groups, and the magnitude of the response was greater (P < 0.0001) in mares with high BCS than in mares with low BCS. In summary,low BCS in mares was associated with a consistent seasonal anovulatory state that was affected little by eST and GnRHa administration. In contrast, all but one mare with high BCS continued to experience estrous cycles and(or) have abundant follicular activity on their ovaries. The IGF-I response to eST treatment was also reduced in mares with low BCS, as was the basal leptin concentration and leptin response to dexamethasone. Although low BCS and leptin concentrations were associated with inactive ovaries during winter and early spring, mares with low BCS eventually ovulated in April and May while leptin concentrations remained low.

The relationship between body condition, leptin, and reproductive and hormonal characteristics of mares during the seasonal anovulatory period

An experiment was conducted to determine the effects of high vs low body condition scores (BCS) produced by restricted feeding on reproductive characteristics, hormonal secretion, and leptin concentrations in mares during the autumnal transition and winter anovulatory period. Mares with BCS of 6.5 to 8.0 were maintained on pasture and/or grass hay, and starting in September, were full fed or restricted to produce BCS of 7.5 to 8.5 (high) or 3.0 to 3.5 (low) by December. All but one mare with high BCS continued to ovulate or have follicular activity during the winter, whereas mares with low BCS went reproductively quiescent. Plasma leptin concentrations varied widely before the onset of restriction, even though all mares were in good body condition. During the experiment, leptin concentrations gradually decreased (P < 0.0001) over time in both groups, but were higher (P < 0.009) in mares with high vs low BCS after 6 wk of restriction, regardless of initial concentration. No differences (P > 0.1) between groups were detected for plasma concentrations of LH, FSH, TSH, GH, glucose, or insulin in samples collected weekly; in contrast, plasma prolactin concentrations were higher (P < 0.02) in mares with high BCS, but also decreased over time (P < 0.008). Plasma IGF-I concentrations tended (P = 0.1) to be greater in mares with high vs low BCS. The prolactin response to sulpiride injection on January 7 did not differ (P > 0.1) between groups. During 12 h of frequent blood sampling on January 12, LH concentrations were higher (P < 0.0001), whereas GH concentrations (P < 0.0001) and response to secretagogue (EP51389; P < 0.03) were lower in mares with high BCS. On January 19, the LH response to GnRH was higher (P < 0.02) in mares with high BCS; the prolactin response to TRH also was higher (P < 0.01) in mares with high BCS. In conclusion, nutrient restriction resulting in low BCS in mares resulted in a profound seasonal anovulatory period that was accompanied by lower leptin, IGF-I, and prolactin concentrations. All but one mare with high BCS continued to cycle throughout the winter or had significant follicular activity on the ovaries. Although leptin concentrations on average are very low in mares with low BCS and higher in well-fed mares, there is a wide variation in concentrations among well-fed mares, indicating that some other factor(s) may determine leptin concentrations under conditions of high BCS.

Penetrating colon injuries requiring resection: diversion or primary anastomosis? An AAST prospective multicenter study

BACKGROUND

The management of colon injuries that require resection is an unresolved issue because the existing practices are derived mainly from class III evidence. Because of the inability of any single trauma center to accumulate enough cases for meaningful statistical analysis, a multicenter prospective study was performed to compare primary anastomosis with diversion and identify the risk factors for colon-related abdominal complications.

METHODS

This was a prospective study from 19 trauma centers and included patients with colon resection because of penetrating trauma, who survived at least 72 hours. Multivariate logistic regression analysis was used to compare outcomes in patients with primary anastomosis or diversion and identify independent risk factors for the development of abdominal complications.

RESULTS

Two hundred ninety-seven patients fulfilled the criteria for inclusion and analysis. Overall, 197 patients (66.3%) were managed by primary anastomosis and 100 (33.7%) by diversion. The overall colon-related mortality was 1.3% (four deaths in the diversion group, no deaths in the primary anastomosis group, p = 0.012). Colon-related abdominal complications occurred in 24% of all patients (primary repair, 22%; diversion, 27%; p = 0.373). Multivariate analysis including all potential risk factors with p values < 0.2 identified three independent risk factors for abdominal complications: severe fecal contamination, transfusion of > or = 4 units of blood within the first 24 hours, and single-agent antibiotic prophylaxis. The type of colon management was not found to be a risk factor. Comparison of primary anastomosis with diversion using multivariate analysis adjusting for the above three identified risk factors or the risk factors previously described in the literature (shock at admission, delay > 6 hours to operating room, penetrating abdominal trauma index > 25, severe fecal contamination, and transfusion of > 6 units blood) showed no statistically significant difference in outcome. Similarly, multivariate analysis and comparison of the two methods of colon management in high-risk patients showed no difference in outcome.

CONCLUSION

The surgical method of colon management after resection for penetrating trauma does not affect the incidence of abdominal complications, irrespective of associated risk factors. Severe fecal contamination, transfusion of > or = 4 units of blood within the first 24 hours, and single-agent antibiotic prophylaxis are independent risk factors for abdominal complications. In view of these findings, the reduced quality of life, and the need for a subsequent operation in colostomy patients, primary anastomosis should be considered in all such patients.

Combination therapy that targets secondary pulmonary changes after abdominal trauma

After abdominal trauma, the lung is susceptible to secondary injury caused by acute neutrophil (PMN) sequestration and alveolar capillary membrane disruption. Adenosine is an endogenous anti-inflammatory metabolite that decreases PMN activation. AICAR ([5-amino-1-[beta-D-ribofuranosyl]imidazole-4-carboxamide]riboside) is the prototype of a novel class of anti-inflammatory drugs that increase endogenous adenosine. After trauma, AICAR administration has been shown to decrease secondary lung injury in models of hemorrhagic shock with delayed lipopolysaccharide challenge and pulmonary contusion. However, early suppression of PMN activation could worsen outcomes after penetrating abdominal trauma. We hypothesized that, after penetrating abdominal trauma, the ideal resuscitation strategy would involve early, short-lived suppression of PMN activation to minimize secondary lung injury, followed by later enhancement of PMN chemotaxis and phagocytosis [using granulocyte colony-stimulating factor (G-CSF)] to lessen late septic complications. G-CSF has not been shown to potentiate PMN mediated pulmonary reperfusion injury. Swine were subjected to cecal ligation/incision and hemorrhagic shock (trauma), followed by resuscitation with shed blood, crystalloid, and either G-CSF, a combination of G-CSF and AICAR, or 0.9% normal saline. At 72 h, bronchoalveolar lavage (BAL) leukocyte counts and protein concentration were determined, and lung tissue analysed for myeloperoxidase (MPO, a measure of PMN infiltration) and microscopic pathology. Analysis of BALs revealed a significant increase protein concentrations and in white blood cell and PMN infiltration (P< 0.05) following trauma. These acute changes were not exacerbated by G-CSF, but were reversed by combined AICAR + G-CSF, which implicates a physiologic role for adenosine. This suggests that combination therapy may have beneficial effects on the lung after trauma.

A novel two-color flow cytometric assay for the detection of Cryptosporidium in environmental water samples

BACKGROUND

Cryptosporidium is an important waterborne pathogen. Detection of Cryptosporidium in concentrated water samples depends on oocyst isolation using immunomagnetic separation (IMS) and/or fluorescence-activated cell sorting (FACS), followed by confirmation using immunofluorescence staining (IFA) and fluorescence microscopy. These methods require highly trained microscopists for oocyst identification and confirmation. Analysis is hampered due to the presence of autofluorescent particles coupled with particles binding nonspecifically with the monoclonal antibodies (mAbs) used for detection. Flow cytometry (FCM) has the potential to be a more specific method for oocyst detection, but such a system would require more than one selection parameter.

METHODS

Various mAbs from commercial suppliers were paired with CRY104-PE and evaluated. The mAb combination that best discriminated stained oocyst from detritus was optimized and compared to Cryptosporidium detection utilizing one-color IFA/FACS.

RESULTS

A highly specific two-color assay employing the IgG(1) mAb CRY104 was developed. The assay resulted in reductions, up to 20-fold, in the number of non-Cryptosporidium particles detected. The addition of a second selection parameter improved microscopic analysis times and simplified oocyst confirmation by microscopists.

CONCLUSIONS

A two-color assay employing competing surface mAbs reduces the number of fluorescent particles sorted, thus improving FCM detection methods for Cryptosporidium.

Endogenous adenosine and secondary injury after chest trauma

BACKGROUND

No previous studies have examined actions of adenosine or related compounds after blunt chest trauma, but we have shown that the prototype adenosine-regulating agent, acadesine (aminoimidazole carboxamide ribonucleotide [AICAR]), has multiple favorable anti-inflammatory actions after other forms of trauma, ischemia, hemorrhage, and sepsis; and that a progressive inflammatory response in the contralateral (uninjured) lung after unilateral blunt chest trauma is caused (in part) by activation and sequestration of circulating leukocytes (white blood cells [WBCs]). Thus, we hypothesized that AICAR would ameliorate WBC-dependent, secondary pathophysiologic changes after blunt chest trauma.

METHODS

Mongrel pigs (28+/-1 kg, n = 21) were anesthetized, mechanically ventilated, and injured on the right chest (pulmonary contusion) with a captive bolt gun. Either AICAR (1 mg/kg + 0.2 mg/kg/min) or its saline vehicle were administered for a 12-hour period, beginning 15 minutes before injury.

RESULTS

Injury caused a three- to fourfold increase in bronchoalveolar lavage (BAL) WBC counts, 10- to 20-fold increases in BAL protein, and 200% increases in lung edema as measured by wet-dry ratio (all p < 0.05), in both the injured (right) and the noninjured (left) lungs. With AICAR versus saline, BAL WBC counts, lung myeloperoxidase levels, and systemic hemodynamics were similar. However, the increases in BAL protein were attenuated by 30% to 50% (p < 0.14, NS) and edema was reduced (p < 0.05) in both lungs. Furthermore, oxygenation, hypercapnia, acidosis (all p < 0.05), and survival were improved (9 of 10 vs. 4 of 11, p < 0.04).

CONCLUSION

Pretreatment with AICAR before experimental pulmonary contusion ameliorates the trauma-induced destruction of the alveolar capillary membrane, and attenuates the delayed secondary injury in the contralateral uninjured lung, by a mechanism that may be independent of leukocytes. Endogenous adenosine could have a role in the pathophysiologic response after blunt chest injury, with potential sites of action including the endothelium and alveolar macrophage. Adenosine-regulating agents may have therapeutic potential after blunt chest injury, but further studies are needed in clinically relevant models, with administration begun at the time of resuscitation.

A rapid and accurate closed-tube immunoassay for platelets on an automated hematology analyzer

Accurate and precise platelet counts are important for patients with severe thrombocytopenia or who are receiving chemotherapy. We developed a novel flow cytometric analysis of platelets that may be particularly valuable for assessing the necessity for platelet transfusions. This ImmunoPlt (CD61) assay is based in part on CD61 monoclonal antibody labeling and has been automated and implemented on the CELL-DYN 4000 hematology analyzer. It is well suited for thrombocytopenic specimens, since it reduces interference by nonplatelet particles. It takes less than 5 minutes from closed-tube aspiration to report. Data for more than 350 thrombocytopenic specimens demonstrate that the ImmunoPlt (CD61) assay is more accurate than the optical scatter or the impedance count for specimens with platelet counts between 1 and 60 x 10(3)/microL (1 and 60 x 10(9)/L). The ImmunoPlt (CD61) assay is more precise than the optical scatter or the impedance count for specimens with platelet counts between 1 and 50 x 10(3)/microL (1 and 50 x 10(9)/L).

Pharmacological evidence of inhibitory and disinhibitory neuronal circuits in dorsal cochlear nucleus

The dorsal cochlear nucleus (DCN) is rich in both glycine and GABA inhibitory neurotransmitter systems, and the response properties of its principal cells (pyramidal and giant cells) are strongly shaped by inhibitory inputs. For example, DCN principal cells often display highly nonmonotonic (so-called type IV) input-output functions in response to best-frequency (BF) tones. In this study, the inhibitory inputs onto the principal cell types and onto response types of known inhibitory interneurons were compared before and during iontophoretic application of the glycine- and GABA(A)-receptor antagonists, strychnine and bicuculline. Strychnine eliminates the central (on-BF) inhibitory area in type IV units, resulting in monotonic BF rate-level curves. Unexpectedly, bicuculline primarily enhances inhibition in principal-cell types; for example, type IV units are inhibited at lower sound levels in the presence of bicuculline. Principal cell types with weaker inhibitory inputs (type IV-T and type III units) are more strongly inhibited in the presence of bicuculline and usually are converted into type IV units. This enhancement of on-BF inhibition by bicuculline suggests a disinhibitory process involving GABA(A) action on a non-GABA(A)ergic inhibitory pathway. This latter pathway is probably glycinergic and involves type II units (deep-layer vertical cells) and/or complex-spiking units (superficial cartwheel cells) because both of these unit types are disinhibited by bicuculline. One intrinsic GABA(A) source could be the superficial stellate cells in DCN because bicuculline partly blocks the inhibition evoked by somatosensory-stimulated activation of the superficial granule-cell circuitry in DCN. Taken together, the results suggest that glycinergic circuits mediate directly the inhibition of DCN principal cells, but that GABA(A)ergic circuits modulate the strength of the inhibition.

Secondary abdominal compartment syndrome: an underappreciated manifestation of severe hemorrhagic shock

OBJECTIVE

Abdominal compartment syndrome (ACS) has multiple well-described etiologies, but almost no attention has focused on ACS in the absence of abdominal injury. This study describes a secondary ACS that occurs after severe hemorrhagic shock with no evidence of abdominal injury.

METHODS

The trauma registry at a Level I trauma center was reviewed for a 13-month period beginning July 1, 1997.

RESULTS

During the study period, there were 46 of 1,216 intensive care unit admissions (4%) who required laparotomy and mesh closure of the abdominal wall because of visceral edema. In that subgroup, six patients (13% of mesh closures, 0.5% intensive care unit admissions) had hemorrhagic shock (5/1, blunt/penetrating trauma) but no evidence of intra-abdominal injury. Associated extremity compartment syndrome developed in two of six (33%). Overall mortality was four of six (67%), secondary to sepsis (n = 3), and head injury (n = 1). Time from admission to decompression averaged 3 hours in survivors and 25 hours in nonsurvivors (overall average = 18+/-9 hours). Resuscitation volume before abdominal decompression averaged 19+/-5 liters of crystalloid and 29+/-10 units of packed red blood cells. Bladder pressure averaged 33+/- 3 mm Hg. Decompression significantly improved peak inspiratory pressure (p < 0.003) and base deficit (p < 0.003).

CONCLUSION

ACS can occur with no abdominal injury; The incidence of secondary ACS was 0.5% in this cohort trauma intensive care unit patients, so it probably occurs more frequently than is currently appreciated. Because survivors were decompressed 20 hours before nonsurvivors, early recognition might improve outcomes. On the basis of these observations, we recommend that bladder pressures should be routinely checked and acted on appropriately when resuscitation volumes approach 10 liters of crystalloid or 10 units of packed red cells.

Spectral integration by type II interneurons in dorsal cochlear nucleus

The type II unit is a prominent inhibitory interneuron in the dorsal cochlear nucleus (DCN), most likely recorded from vertical cells. Type II units are characterized by low rates of spontaneous activity, weak responses to broadband noise, and vigorous, narrowly tuned responses to tones. The weak responses of type II units to broadband stimuli are unusual for neurons in the lower auditory system and suggest that these units receive strong inhibitory inputs, most likely from onset-C neurons of the ventral cochlear nucleus. The question of the definition of type II units is considered here; the characteristics listed in the preceding text define a homogeneous type II group, but the boundary between this group and other low spontaneous rate neurons in DCN (type I/III units) is not yet clear. Type II units in decerebrate cats were studied using a two-tone paradigm to map inhibitory responses to tones and using noisebands of varying width to study the inhibitory processes evoked by broadband stimuli. Iontophoresis of bicuculline and strychnine and comparisons of two-tone responses between type II units and auditory nerve fibers were used to differentiate inhibitory processes occurring near the cell from two-tone suppression in the cochlea. For type II units, a significant inhibitory region is always seen with two-tone stimuli; the bandwidth of this region corresponds roughly to the previously reported excitatory bandwidth of onset-C neurons. Bandwidth widening experiments with noisebands show a monotonic decline in response as the bandwidth increases; these data are interpreted as revealing strong inhibitory inputs with properties more like onset-C neurons than any other response type in the lower auditory system. Consistent with these properties, iontophoresis of inhibitory antagonists produces a large increase in discharge rate to broadband noise, making tone and noise responses nearly equal.

Granulocyte colony-stimulating factor and neutrophil-related changes in local host defense during recovery from shock and intra-abdominal sepsis

BACKGROUND

We have reported that treatment with exogenous granulocyte colony-stimulating factor (G-CSF) improves abscess localization and reduces mortality without aggravating neutrophil (PMN)-mediated reperfusion injury in a model of septic abdominal trauma. The purpose of this study was to determine actions of G-CSF on PMN function in the peritoneum.

METHODS

Anesthetized swine were pretreated with broad-spectrum antibiotics and underwent cecal ligation and incision and 35% hemorrhage (trauma). After 1 hour they were resuscitated with shed blood, crystalloid, and either G-CSF (n = 10) or saline solution vehicle (n = 9). The animals were observed for 72 hours.

RESULTS

After trauma, saline solution treatment increased PMN infiltration into the peritoneum within 2 hours (P = .035), increased peritoneal PMN elastase production (i.e., cytotoxicity) by 24 hours (P = .004), and decreased adherence of peritoneal PMNs to an artificial substrate from 4 to 72 hrs (P = .043). The mean autopsy score was 7.0 +/- 0.5. With G-CSF treatment peritoneal neutrophilia was enhanced (maximum 48 hours, P = .002) and PMN cytotoxicity was augmented and delayed (maximum 48 hours, P = .004). Despite these changes, adherence of peritoneal PMNs was not significantly changed and there was no evidence for PMN-mediated damage in the lung as judged by bronchoalveolar lavage protein, bronchoalveolar lavage PMNs, lung tissue myeloperoxidase, or histologic changes. The mean autopsy score was improved to 4.1 +/- 0.3 (P < .001).

CONCLUSIONS

G-CSF in resuscitation fluids improved localization of an intra-abdominal septic focus by increased production of circulating PMNs, increased PMN extravasation into the peritoneal cavity, and increased PMN cytotoxicity at the abdominal septic focus, without exaggerating PMN-dependent reperfusion injury in the lung. Therefore these data further support the idea that G-CSF in resuscitation fluids might reduce septic complications in the multiply injured trauma patient.

Single-unit responses in the inferior colliculus of decerebrate cats. I. Classification based on frequency response maps

This study proposes a classification system for neurons in the central nucleus of the inferior colliculus (ICC) that is based on excitation and inhibition patterns of single-unit responses in decerebrate cats. The decerebrate preparation allowed extensive characterization of physiological response types without the confounding effects of anesthesia. The tone-driven discharge rates of individual units were measured across a range of frequencies and levels to map excitatory and inhibitory response areas for contralateral monaural stimulation. The resulting frequency response maps can be grouped into the following three populations: type V maps exhibit a wide V-shaped excitatory area and no inhibition; type I maps show a more restricted I-shaped region of excitation that is flanked by inhibition at lower and higher frequencies; and type O maps display an O-shaped island of excitation at low stimulus levels that is bounded by inhibition at higher levels. Units that produce a type V map typically have a low best frequency (BF: the most sensitive frequency), a low rate of spontaneous activity, and monotonic rate-level functions for both BF tones and broadband noise. Type I and type O units have BFs that span the cat's range of audible frequencies and high rates of spontaneous activity. Like type V units, type I units are excited by BF tones and noise at all levels, but their rate-level functions may become nonmonotonic at high levels. Type O units are inhibited by BF tones and noise at high levels. The existence of distinct response types is consistent with a conceptual model in which the unit types receive dominant inputs from different sources and shows that these functionally segregated pathways are specialized to play complementary roles in the processing of auditory information.

Single-unit responses in the inferior colliculus of decerebrate cats. II. Sensitivity to interaural level differences

Single units in the central nucleus of the inferior colliculus (ICC) of unanesthetized decerebrate cats can be grouped into three distinct types (V, I, and O) according to the patterns of excitation and inhibition revealed in contralateral frequency response maps. This study extends the description of these response types by assessing their ipsilateral and binaural response map properties. Here the nature of ipsilateral inputs is evaluated directly using frequency response maps and compared with results obtained from methods that rely on sensitivity to interaural level differences (ILDs). In general, there is a one-to-one correspondence between observed ipsilateral input characteristics and those inferred from ILD manipulations. Type V units receive ipsilateral excitation and show binaural facilitation (EE properties); type I and type O units receive ipsilateral inhibition and show binaural excitatory/inhibitory (EI) interactions. Analyses of binaural frequency response maps show that these ILD effects extend over the entire receptive field of ICC units. Thus the range of frequencies that elicits excitation from type V units is expanded with increasing levels of ipsilateral stimulation, whereas the excitatory bandwidth of type I and O units decreases under the same binaural conditions. For the majority of ICC units, application of bicuculline, an antagonist for GABAA-mediated inhibition, does not alter the basic effects of binaural stimulation; rather, it primarily increases spontaneous and maximum discharge rates. These results support our previous interpretations of the putative dominant inputs to ICC response types and have important implications for midbrain processing of competing free-field sounds that reach the listener with different directional signatures.

Mediator-dependent secondary injury after unilateral blunt thoracic trauma

The pathophysiologic sequence leading to respiratory failure after chest trauma can be an inevitable consequence of the primary injury or a secondary, mediator-driven inflammatory process. To distinguish between these alternatives, a simple cross-transfusion experiment was performed. A captive bolt gun injured the chest of anesthetized pigs that were mechanically ventilated with FiO2 = .21, .50, or .50 plus indomethacin (5 mg/kg intravenous; 15 min before injury). Tube thoracostomy immediately followed. After 30 min, blood from these injured donors was transfused into three matched groups of naive recipients (n = 8, 6, and 4, respectively) for a 33% exchange transfusion. Two control groups received blood from uninjured donors with tube thoracostomies only (FiO2 = .21, n = 7; FiO2 = .50, n = 10). Within 15-30 min after transfusion, in recipients from injured donors versus controls, lung compliance was decreased 20%, stroke volume and cardiac output were decreased 50%, and pulmonary vascular resistance was increased >300% (all p < .05). These changes recovered to baseline within 60-90 min. The stable metabolite of thromboxane A2, thromboxane B2, increased >500% in plasma within 15 min and remained elevated for >120 min. All responses were similar at 21 % or 50% O2, which suggests that hypoxia per se is not a cause of mediator production. All responses were eliminated by indomethacin. By 24 h, histologic changes included atelectasis in 3/3 recipients from injured donors versus 0/3 recipients from uninjured donors. We conclude that 1) blunt chest trauma releases blood borne mediators, including prostanoids; 2) these mediators can cause secondary cardiopulmonary changes in naive recipients similar to those produced by chest trauma; 3) the progression to trauma-induced respiratory failure is multifactorial; 4) early pharmacologic intervention, rather than supportive care alone, may benefit some victims of severe chest trauma.

Prostanoids: early mediators in the secondary injury that develops after unilateral pulmonary contusion

BACKGROUND

We have previously shown a sequence of events after unilateral pulmonary contusion that suggests the release of blood-borne prostanoid mediators and that culminates in refractory bilateral pulmonary failure.

PURPOSE

To determine the role of platelet-derived thromboxane and endothelial-derived prostacyclin in the primary and secondary injury after unilateral blunt chest trauma, and to determine whether pretreatment with the cyclooxygenase inhibitor indomethacin alters the progression of secondary injury.

METHODS

Anesthetized, ventilated (FIO2 = 0.50) pigs received a unilateral, blunt injury to the right thorax (n = 20) or sham injury (n = 5) and were monitored for 24 hours. Either indomethacin (5 mg/kg i.v.; n = 10) or its saline vehicle (n = 10) were administered 15 minutes before injury. Serial bronchoalveolar lavages of each lung were analyzed for protein and neutrophil (polymorphonuclear neutrophil (PMN)) content.

RESULTS

Contusion caused profound hypoxemia; PaO2 partially recovered within 1 hour of injury to 50% of baseline. Thereafter, worsening hypoxemia required positive end-expiratory pressure. With indomethacin compared with vehicle, PaO2 was higher at any given level of positive end-expiratory pressure (p < 0.05). There was an early increase in serial bronchoalveolar lavage protein on the injured side (peak at 2 hours), with a delayed pulmonary capillary leak on the contralateral side (peak at 6 hours), which correlated with increasing PMN infiltration; this was reduced by 40 to 60% with indomethacin (p < 0.05). Thromboxane peaked within 1 hour after contusion at 800% baseline, then fell off rapidly. This peak preceded the maximal increase in permeability and was completely blocked by indomethacin. Prostacyclin slowly rose to 300% baseline by 3 hours and remained elevated; this change was blocked by indomethacin for 18 hours.

CONCLUSIONS

Contusion of the right thorax induced a delayed pulmonary capillary leak in the left lung, which reflects a progressive secondary inflammatory response. Elevations in thromboxane and prostacyclin preceded progressive bilateral PMN infiltration. Indomethacin blocked thromboxane and prostacyclin and attenuated, but did not prevent, the progression to pulmonary failure. Overall, these data suggest that prostanoids are released soon after unilateral contusion and initiate an inflammatory response in both lungs that is sustained by PMN infiltration.

Early and late acute respiratory distress syndrome: two distinct clinical entities

BACKGROUND

Despite numerous advances in surgical critical care and ventilatory management, mortality rates for acute respiratory distress syndrome (ARDS) have remained relatively constant. Pressure-limited and non-pressure-limited ventilatory techniques have been advocated with disparate results. We hypothesized that there are two forms of ARDS, which may account for the conflicting clinical reports.

METHODS

Patients with posttraumatic ARDS were identified and reviewed. ARDS was defined as PaO2/FiO2 ratio less than 200 with diffuse bilateral infiltrates on chest radiograph and no congestive heart failure. Patients were analyzed relative to injury mechanism, transfusions, fluid balance, presence of pneumonia (defined as > or =10(5) colony-forming units/mL in bronchoalveolar lavage effluent), and outcome. All were managed with a non-pressure-limited strategy.

RESULTS

During a 5.5-year period, 178 patients with posttraumatic ARDS were identified. Mean Injury Severity Score and age were 29 and 40 years, respectively. Patients were stratified by time of ARDS diagnosis. Eighty-two patients (46%) had early ARDS (within 48 hours after admission), and 96 patients (54%) had late ARDS (>48 hours between admission and diagnosis). There were no differences in Injury Severity Score, but the late group was significantly older. The early ARDS group was characterized by profound hemorrhagic shock and had significant differences from the late group in incidence of penetrating injury (30 vs. 10%; p<0.001), admission base deficit (-7.7 vs. -4.2 mEq/L; p<0.001), 48-hour transfusions (19.7 vs. 9.4; p<0.0001), initial 5-day fluid balance (19.9 vs. 10.1 L; p<0.0001), and initial PaO2/FiO2 (121 vs. 141; p<0.007). Pneumonia before ARDS was significantly associated with late ARDS (38 vs. 9%; p<0.001). ARDS-related mortality was primarily caused by hemorrhagic shock in the early group and progressive multiple organ failure in the late group.

CONCLUSION

There are two distinct forms of posttraumatic ARDS. Early ARDS is characterized by hemorrhagic shock with capillary leak. Late ARDS frequently follows pneumonia and is associated with multiple system injury. Further studies should differentiate between these two distinct syndromes.

Normal human CD4+ memory T cells display broad heterogeneity in their activation threshold for cytokine synthesis

CD4+ memory T cells coordinate immune responses against viruses and other pathogens via the Ag-induced secretion of potent effector cytokines. The efficacy of these responses depends on both the overall number of pathogen-specific memory T cells and the particular array of cytokines that these cells are programmed to secrete. Here, we provide evidence that heterogeneity in Ag triggering thresholds constitutes an additional critical determinant of memory T cell function. Using a novel assay that allows single-cell detection of Ag-specific T cell cytokine production, we demonstrate that CMV-specific CD4+ memory cells from human peripheral blood display pronounced differences in their costimulatory requirements for Ag-induced triggering of IFN-gamma and IL-2 secretion, ranging from cells that trigger with little costimulation (e.g., resting APC alone) to cells requiring potent costimulation through multiple pathways (resting APC plus multiple costimulatory mAbs, or activated APC). These differences in costimulatory requirements are independent of clonal differences in TCR signaling intensity, consistent with an intrinsic activation-threshold heterogeneity that is "downstream" from the TCR. Thus, "effective" frequencies of Ag-specific CD4+ memory T cells appear to depend on the activation status of available APC, a dependence that would allow the immune system to rapidly adjust the number of functional Ag-specific memory T cells in a particular effector site according to local conditions.

Determination of CD4 antigen density on cells: role of antibody valency, avidity, clones, and conjugation

The number of R-phycoerythrin (R-PE)-conjugated antibodies bound to a cell can be quantitated on a flow cytometer by using beads with known numbers of attached R-PE molecules (QuantiBRITE PE). Using these reference beads, we have observed that a number of factors affect the accuracy of the quantitation and conclusions about epitope density. These factors include valence of antibody binding, the use of antibody fragments (Fab's) versus intact monoclonal antibodies (mAb's), fixation, the purity of the conjugate (i.e., percentage of 1:1 ratios), dissociation rate, the use of washed versus unwashed preparations, and the location of epitope on target antigen. We used CD4 on T cells as a model to explore these challenges in detail. We conclude that CD4+ T cells bind approximately 49,000 CD4 (Leu 3a) antibody molecules, that this binding is bivalent, and therefore that there are approximately 98,000 CD4 antigen molecules on the surface of these cells.

Quantitation of CD38 expression using QuantiBRITE beads

The QuantiBRITE bead method was compared with the CD4 biological calibration method for quantitation of CD38 expression on CD8+ T-lymphocytes of Multicenter AIDS Cohort Study participants. Results were expressed as CD38 antibodies bound per cell (ABCs) and were the same with the two methods provided two conditions were met. These were the use of repurified (> 95% of the monoclonal antibodies [mAbs] have 1 phycoerythrin [PE] molecule per mAb) CD38-PE for both methods and use of repurified CD4-PE to calculate the relative fluorescence intensity multiplier for the CD4 biological calibration method. Our results indicate that the prognostic significance of CD38 values obtained using the QuantiBRITE method can be interpreted using previously published reports (Liu et al.: J Acquir Immune Defic Syndr Hum Retrovirol 16:83-92, 1997 and 18:332-340, 1998). Sample preparation using NH4Cl and FACS lysing solution gave similar results for CD38 relative fluorescence intensity. Dilution into either phosphate-buffered saline with 2% fetal calf serum and 0.1% sodium azide or fixation in 1% paraformaldehyde for 1 or 24 h also gave similar results. In experiments using Raji cells, which express high levels of CD38, the valence of binding of the intact Leu 17 antibody was approximately 68% bivalent and approximately 32% monovalent. This emphasizes the complexity of determining antigen density from ABCs. We conclude that repurified PE conjugates of CD38, which can be consistently made, together with QuantiBRITE PE beads, provide a convenient and reliable method for quantitation of CD38 expression as ABCs.

Staining of cell surface human CD4 with 2'-F-pyrimidine-containing RNA aptamers for flow cytometry

We have used recombinant human CD4 presented on beads as an affinity matrix to screen a 2'-F-pyrimidine-containing RNA library with a complexity of approximately 10(14) molecules. Affinity-selected aptamers bind recombinant CD4 with low nanomolar equilibrium dissociation constants. These high-affinity aptamers conjugated to different fluorophores such as fluorescein and phycoerythrin were used to stain cells, expressing human CD4 on cell surface, for analysis by flow cytometry. Aptamers, conjugated to fluorophores, stained mouse T cells that express human CD4 on the surface, but not the control mouse T cells lacking human CD4. The control cells, however, do express mouse CD4 whose extracellular domain has 55% sequence identity to the human form. These human CD4-specific aptamers selectively stained CD4(+) T cells in a preparation of human peripheral blood mononuclear cells. These results and others suggest that aptamers are emerging as a versatile class of molecules that can be used for various diagnostic applications performed under different formats or platforms.

Acetylcholine metabolism in the inflamed rat intestine

Acetylcholine (ACh) is a major neurotransmitter in the enteric nervous system. Since increasing evidence suggests that inflammation alters neural regulation of intestinal function, we examined the synthesis and breakdown of ACh in smooth muscle/myenteric plexus (SM/MP) preparations from the jejunum of the rat during inflammation caused by infection with the nematode parasite Trichinella spiralis. Both total and neuron-specific uptake of the ACh precursor [3H]choline into SM/MP preparations was increased by over twofold on Day 6 postinfection. Further, a radiochemical assay of choline acetyltransferase activity showed significant increase by Day 1, with peak values reached by Day 3 and maintained without reversal thereafter. Despite the enhancement of these steps, measurement of the conversion of [3H]choline into [3H]ACh in SM/MP preparations in vitro showed a nearly fourfold decrease by Day 6, implying a large decrease in ACh production in the inflamed jejunum. Examination of acetylcholinesterase in the rat jejunum showed decreased histochemical staining intensity in the muscle wall, and quantitative evaluation showed significantly decreased (>50%) acetylcholinesterase activity in SM/MP preparations. These results show that cholinergic innervation of the intestine can undergo rapid and long-lasting alterations during inflammation. Upregulation of major steps in the synthetic pathway for ACh was not matched by increased ACh production, suggesting that defects in ACh packaging, storage, and granule exocytosis may also be present.

Improved success in nonoperative management of blunt splenic injuries: embolization of splenic artery pseudoaneurysms

OBJECTIVES

By using abdominal computed tomographic scans in the evaluation of blunt splenic trauma, we previously identified the presence of vascular blush as a predictor of failure, with a failure of nonoperative management of 13% in that series. This finding led to an alteration in our management scheme, which now includes the aggressive identification and embolization of splenic artery pseudoaneurysms.

METHODS

The medical records of 524 consecutive patients with blunt splenic injury managed over a 4.5-year period were reviewed for the following information: age, Injury Severity Score (ISS), American Association for the Surgery of Trauma splenic injury grade (SIG), method and outcome of management.

RESULTS

Of the patients, 66% were male with a mean age of 32 +/- 16, and mean ISS of 25 +/- 13. A total of 180 patients (34%) were managed with urgent operation on admission (81% splenectomy (SIG 4.0), 19% splenorrhaphy (SIG 2.6)). The remaining 344 patients (66%) were hemodynamically stable and underwent computed tomographic scan and planned nonoperative management. Of these patients, 322 patients (94%) were successfully managed nonoperatively (61% of total splenic injuries). In 26 patients (8%), a contrast blush identified on computed tomographic scan was confirmed as a parenchymal pseudoaneurysm on arteriography. Twenty patients (SIG, 2.8) were successfully embolized. In six patients, technical failure precluded embolization; all required splenectomy (SIG, 4.0). A total of 22 patients (6%) failed nonoperative management, including the six with unsuccessful embolization attempts. Sixteen patients (SIG, 3.0) who had no evidence of pseudoaneurysm were explored for a falling hematocrit, hemodynamic instability, or a worsening follow-up computed tomography: 13 patients had splenectomy, and three patients had splenorrhaphy.

CONCLUSIONS

Aggressive surveillance for and embolization of posttraumatic splenic artery pseudoaneurysms improved the rate of successful nonoperative management of blunt splenic trauma to 61%, with a nonoperative failure rate of only 6%. In comparison with our previous work, this reduction in failure of nonoperative management is a significant improvement (p < 0.03).

Prospective study of blunt aortic injury: helical CT is diagnostic and antihypertensive therapy reduces rupture

OBJECTIVE

There were two aims of this study. The first was to evaluate the application of helical computed tomography of the thorax (HCTT) for the diagnosis of blunt aortic injury (BAI). The second was to evaluate the efficacy of beta-blockers with or without nitroprusside in preventing aortic rupture.

SUMMARY BACKGROUND DATA

Aortography has been the standard for diagnosing BAI for the past 4 decades. Conventional chest CT has not proven to be of significant value. Helical CT scanning is faster and has higher resolution than conventional CT. Retrospective studies have suggested the efficacy of antihypertensives in preventing aortic rupture.

METHODS

A prospective study comparing HCTT to aortography in the diagnosis of BAI was performed. A protocol of beta-blockers with or without nitroprusside was also examined for efficacy in preventing rupture before aortic repair and in allowing delayed repair in patients with significant associated injuries.

RESULTS

Over a period of 4 years, 494 patients were studied. BAI was diagnosed in 71 patients. Sensitivity was 100% for HCTT versus 92% for aortography. Specificity was 83% for HCTT versus 99% for aortography. Accuracy was 86% for HCTT versus 97% for aortography. Positive predictive value was 50% for HCTT versus 97% for aortography. Negative predictive value was 100% for HCTT versus 97% for aortography. No patient had spontaneous rupture in this study.

CONCLUSIONS

HCTT is sensitive for diagnosing intimal injuries and pseudoaneurysms. Patients without direct HCTT evidence of BAI require no further evaluation. Aortography can be reserved for indeterminate HCTT scans. Early diagnosis with HCTT and presumptive treatment with the antihypertensive regimen eliminated in-hospital aortic rupture.

Development and evaluation of computer-based training for pre/post human immunodeficiency virus test counseling

Computer-based instruction provides flexibility for staff development in the context of downsizing and rapid change in hospitals. There is an increasing need for nurse involvement in human immunodeficiency virus test counseling in hospitals and clinics because the Centers for Disease Control has recommended that human immunodeficiency virus testing be offered to all pregnant women. In this article, the author describes the development and evaluation of a computer-based instruction program to train nurses in human immunodeficiency virus test counseling.

A flow cytometric immunoassay for beta2-microglobulin in whole blood

Flow cytometers can discriminate a single particle type in an unwashed whole blood sample. Utilizing this capability. we devised a homogeneous bead-immobilized sandwich immunoassay for soluble beta2M (beta2-microglobulin) in whole blood, utilizing an antibody that discriminates soluble from cellular beta2M. A 4 microm bead was chosen that fluoresces only in a FACScan flow cytometer's FL3 channel. thus allowing triggering on this bead to the exclusion of the many blood cell events. The bead was adsorbed with a capture antibody (clone A7801) which binds only to soluble and not to cellular beta2M. This antibody appears to recognize an epitope on beta2M which interfaces to the heavy chain of cellular Class I MHC molecules. The signal antibody (PE conjugate of clone L376, emitting in the FL2 channel) binds to both soluble and cellular beta2M (present in roughly equal amounts in normal blood). The various parameters required for a flow cytometric immunoassay were optimized. The 4 microm sized bead was adequately large to give a near full scale signal at saturation. The relative amounts of signal antibody and capture beads were balanced to give a low blank, minimal 'hook effect', and reasonable event rate on the flow cytometer. The amount of blood added was selected to give a signal near the bottom of the immunassay range for normals with the higher range available for clinical samples. The assay requires no washing, minimizes blood handling, and has a working range (2.5 decades) that is compatible with the biological range of beta2M concentrations with a single blood dilution.

P-glycoprotein function involves conformational transitions detectable by differential immunoreactivity

The MDR1 P-glycoprotein (Pgp), a member of the ATP-binding cassette family of transporters, is a transmembrane ATPase efflux pump for various lipophilic compounds, including many anti-cancer drugs. mAb UIC2, reactive with the extracellular moiety of Pgp, inhibits Pgp-mediated efflux. UIC2 reactivity with Pgp was increased by the addition of several Pgp-transported compounds or ATP-depleting agents, and by mutational inactivation of both nucleotide-binding domains (NBDs) of Pgp. UIC2 binding to Pgp mutated in both NBDs was unaffected in the presence of Pgp transport substrates or in ATP-depleted cells, whereas the reactivities of the wild-type Pgp and Pgps mutated in a single NBD were increased by these treatments to the level of the double mutant. These results indicate the existence of different Pgp conformations associated with different stages of transport-associated ATP hydrolysis and suggest trapping in a transient conformation as a mechanism for antibody-mediated inhibition of Pgp.

Granule cell activation of complex-spiking neurons in dorsal cochlear nucleus

Dorsal cochlear nucleus (DCN) principal cells receive, in addition to their well known auditory inputs, various nonauditory inputs via a cerebellar-like granule cell circuit located in the superficial layers of the DCN. Activation of this circuit (granule cell axons make excitatory synapses on the principal cells but also contact inhibitory interneurons that project to the principal cells) produces strong inhibition of the principal cells. Here we investigate the role of cartwheel cells, homologs of cerebellar Purkinje cells, in producing this inhibition. The responses of type IV units (one type of principal cells) and of cartwheel cells were recorded to ortho- and antidromic activation of the granule cells (i. e., by stimulation of their inputs from the somatosensory cuneate and spinal trigeminal nuclei and by direct stimulation of their parallel fiber axons). Cartwheel cells were identified on the basis of recording depth and complex action potential shape. A four-pulse facilitation paradigm (four pulses at 50 msec intervals) was used; this stimulus allows separation of the apparently simple inhibitory somatosensory response of type IV units into a three-component (inhibition-excitation-inhibition) response. As expected, cartwheel cells are excited by granule cell activation; the latencies and four-pulse amplitudes of these responses correspond to the properties of the second, long-latency inhibitory component of type IV responses. The source of the first, short-latency inhibitory response is still unknown. Nevertheless, these results show that cartwheel cells convey inhibitory polysensory information to DCN principal cells.

Evidence of stimulus-dependent correlated activity in the dorsal cochlear nucleus of decerebrate gerbils

Cross-correlation analysis of simultaneously recorded spike trains was used to study the internal organization of the dorsal cochlear nucleus (DCN) of unanesthetized decerebrate Mongolian gerbils. The goal was to test the model (adapted from cat) that its principal cells (type III and type IV units) receive three sources of shared auditory input: excitatory input from the auditory nerve; inhibitory input from DCN interneurons (vertical cells; type II and type II-i units) that respond vigorously to tones; and inhibitory input from ventral cochlear nucleus principal cells (D-stellate cells; wideband inhibitors) that conversely respond vigorously to noise. Records of spontaneous and/or driven activities (to long-duration tones and frozen broadband noise) were obtained for 51 pairs consisting of type II, type III, and type IV units; type III units inhibited by low-level noise were subclassified as type III-i units. Pairs were isolated with two electrodes to study the effect of differences in unit best frequencies (BFs) on correlation. All correlated pairs composed of type III and type IV units (17 of 31 pairs) showed central mounds (CMs), indicative of shared input, in their cross-correlograms. These data exhibited two important properties: pairs with similar BFs were more likely to show CMs, and the shape of the CMs was stimulus dependent. That is, CM width typically changed sharply from wide to narrow with increasing level; significantly, transition-level CMs were either a composite of these shapes or not present. The transition to only narrow CMs occurred above the thresholds of type II and type III-i units to tones, but below their thresholds to noise. Cross-correlograms derived from the tone-evoked activities of pairs involving type II units (3 of 6 pairs) showed inhibitory troughs (ITs); unexpectedly, type III-i units were involved in both IT and CM pairs, suggesting that this unit type may reflect recordings from both vertical and principal cells. Overall, the results are interpretable in terms of the model of gerbil DCN that was adapted from cat, suggesting that the model generalizes across species. Compared with cat, however, gerbil principal cell responses (predominantly type III unit properties) are less dominated by inhibition.

Affinity modulation of platelet integrin alphaIIbbeta3 by beta3-endonexin, a selective binding partner of the beta3 integrin cytoplasmic tail

Platelet agonists increase the affinity state of integrin alphaIIbbeta3, a prerequisite for fibrinogen binding and platelet aggregation. This process may be triggered by a regulatory molecule(s) that binds to the integrin cytoplasmic tails, causing a structural change in the receptor. beta3-Endonexin is a novel 111-amino acid protein that binds selectively to the beta3 tail. Since beta3-endonexin is present in platelets, we asked whether it can affect alphaIIbbeta3 function. When beta3-endonexin was fused to green fluorescent protein (GFP) and transfected into CHO cells, it was found in both the cytoplasm and the nucleus and could be detected on Western blots of cell lysates. PAC1, a fibrinogen-mimetic mAb, was used to monitor alphaIIbbeta3 affinity state in transfected cells by flow cytometry. Cells transfected with GFP and alphaIIbbeta3 bound little or no PAC1. However, those transfected with GFP/beta3-endonexin and alphaIIbbeta3 bound PAC1 specifically in an energy-dependent fashion, and they underwent fibrinogen-dependent aggregation. GFP/beta3-endonexin did not affect levels of surface expression of alphaIIbbeta3 nor did it modulate the affinity of an alphaIIbbeta3 mutant that is defective in binding to beta3-endonexin. Affinity modulation of alphaIIbbeta3 by GFP/beta3-endonexin was inhibited by coexpression of either a monomeric beta3 cytoplasmic tail chimera or an activated form of H-Ras. These results demonstrate that beta3-endonexin can modulate the affinity state of alphaIIbbeta3 in a manner that is structurally specific and subject to metabolic regulation. By analogy, the adhesive function of platelets may be regulated by such protein-protein interactions at the level of the cytoplasmic tails of alphaIIbbeta3.

Modeling inhibition of type II units in the dorsal cochlear nucleus

Type II units in the dorsal cochlear nucleus (DCN) are characterized by vigorous but nonmonotonic responses to best frequency tones as a function of sound pressure level, and relatively weak responses to noise. A model of DCN neural circuitry was used to explore two hypothetical mechanisms by which neurons may be endowed with type II unit response properties. Both mechanisms assume that type II units receive excitatory input from auditory nerve (AN) fibers and inhibitory input from an unspecified class of cochlear nucleus interneurons that also receive excitatory AN input. The first mechanism, a lateral inhibition (LI) model, supposes that type II units receive inhibitory input from a number of narrowly tuned interneurons whose best frequencies (BFs) flank the BF of the type II unit. Tonal stimuli near BF result in only weak inhibitory input, but broadband stimuli recruit enough lateral inhibitors to greatly weaken the type II unit response. The second mechanism, a wideband inhibition (WBI) model, supposes that type II units receive inhibitory input from interneurons that are broadly tuned so that they respond more vigorously to broadband stimuli than to tones. Physiological and anatomical evidence points to the possible existence of such a class of neurons in the cochlear nucleus. The model extends an earlier computer model of an iso-frequency DCN patch to multiple frequency slices and adds a population of interneurons to provide the inhibition to model type II units (called 12-cells). The results show that both mechanisms accurately simulate responses of type II units to tones and noise. An experimental paradigm for distinguishing the two mechanisms is proposed.

Effects of somatosensory and parallel-fiber stimulation on neurons in dorsal cochlear nucleus

1. Single units and evoked potentials were recorded in the dorsal cochlear nucleus (DCN) of paralyzed decerebrate cats in response to electrical stimulation at two sites: 1) in the somatosensory dorsal column nuclei (together called MSN below for medullary somatosensory nuclei), which activates mossy-fiber inputs to granule cells in superficial DCN, and 2) on the free surface of the DCN, which activates granule cell axons (parallel fibers) directly. The goal was to evaluate hypotheses about synaptic interactions in the cerebellum-like circuitry of the superficial DCN. A four-pulse facilitation paradigm was used (50-ms interpulse interval); this allows identification of three components of the responses of DCN principal cells (type IV units) to these stimuli. The latencies of the response components were compared with the latency of the evoked potential in DCN, which signals the arrival of the parallel fiber volley at the recording site. 2. The first component is a short-latency inhibitory response; this component is seen only with MSN stimulation and is seen almost exclusively in units also showing the second component, the transient excitatory response. The short-latency inhibitory component precedes the evoked potential. No satisfactory explanation for the short-latency component can be given at present; it most likely reflects a fast-conducting inhibitory input that arrives at the type IV unit before the slowly conducting parallel fibers. 3. The second component is a transient excitatory response; this component is seen with both MSN and parallel fiber stimulation; it is weak and appears to be masked easily by the inhibitory response components. The excitatory component occurs at the same latency as the evoked potential and probably reflects direct excitation of principal cells by granule cell axons. The excitatory component is seen in about half the type IV units for both stimulating sites. With MSN stimulation, the lack of excitation in some units suggests a heterogeneity of cochlear granule cells, with some carrying somatosensory information and some not carrying this information; with parallel fiber stimulation, excitation probably requires the stimulating and recording electrodes to be lined up on the same "beam" of parallel fibers. 4. The third component is a long-lasting inhibitory response that is observed in virtually all type IV units with both MSN and parallel-fiber stimulation; its latency is longer than the evoked potential. Evidence suggests that it is produced by inhibitory input from cartwheel cells. The appearance of this inhibitory component in almost all type IV units can be accounted for by the considerable spread of cartwheel-cell axons in the direction perpendicular to the parallel fibers. 5. The evoked potential and all three components of the unit response vary systematically in size over the four pulses of the electrical stimulus. These results can be accounted for by two phenomena: 1) a facilitation of the granule cell synapses on all cell types that produces a steadily growing response through the four pulses, resembles presynaptic facilitation, and is seen with both MSN and parallel-fiber stimulation; and 2) a strong reduction in the granule cell response between the first and second pulse for MSN stimulation only. This reduction probably occurs presynaptically in the glomerulus or in the granule cell itself and could reflect inhibitory inputs. 6. The response components described above are seen in type IV units recorded in both the fusiform-cell and deep layers of the DCN; this suggests that both pyramidal and giant cells are activated similarly. The simplest interpretation is that both principal cell types are activated by the cerebellum-like circuitry in superficial DCN. Alternatively, because giant cells appear to make limited contact with the granule-cell circuits of superficial DCN, this finding may suggest the existence of currently undescribed granule cell circuits in deep DCN that are si

Differentiation and stability of T helper 1 and 2 cells derived from naive human neonatal CD4+ T cells, analyzed at the single-cell level

The development of CD4+ T helper (Th) type 1 and 2 cells is essential for the eradication of pathogens, but can also be responsible for various pathological disorders. Therefore, modulation of Th cell differentiation may have clinical utility in the treatment of human disease. Here, we show that interleukin (IL) 12 and IL-4 directly induce human neonatal CD4- T cells, activated via CD3 and CD28, to differentiate into Th1 and Th2 subsets. In contrast, IL-13, which shares many biological activities with IL-4, failed to induce T cell differentiation, consistent with the observation that human T cells do not express IL-13 receptors. Both the IL-12-induced Th1 subset and the IL-4-induced Th2 subset produce large quantities of IL-10, confirming that human IL-10 is not a typical human Th2 cytokine. Interestingly, IL-4-driven Th2 cell differentiation was completely prevented by an IL-4 mutant protein (IL-4.Y124D), indicating that this molecule acts as a strong IL-4 receptor antagonist. Analysis of single T cells producing interferon gamma or IL-4 revealed that induction of Th1 cell differentiation occurred rapidly and required only 4 d of priming of the neonatal CD4+ T cells in the presence of IL-12. The IL-12-induced Th1 cell phenotype was stable and was not significantly affected when repeatedly stimulated in the presence of recombinant IL-4. In contrast, the differentiation of Th2 cells occurred slowly and required not only 6 d of priming, but also additional restimulation of the primed CD4+ T cells in the presence of IL-4. Moreover, IL-4-induced Th2 cell phenotypes were not stable and could rapidly be reverted into a population predominantly containing Th0 and Th1 cells, after a single restimulation in the presence of IL-12. The observed differences in stability of IL-12- and IL-4-induced human Th1 and Th2 subsets, respectively, may have implications for cytokine-based therapies of chronic disease.

Computer simulation of shared input among projection neurons in the dorsal cochlear nucleus

Computer simulations of a network model of an isofrequency patch of the dorsal cochlear nucleus (DCN) were run to explore possible mechanisms for the level-dependent features observed in the cross-correlograms of pairs of type IV units in the cat and nominal type IV units in the gerbil DCN. The computer model is based on the conceptual model (of a cat) that suggests two sources of shared input to DCN's projection neurons (type IV units): excitatory input for auditory nerves and inhibitory input from interneurons (type II units). Use of tonal stimuli is thought to cause competition between these sources resulting in the decorrelation of type IV unit activities at low levels. In the model, P-cells (projection neurons), representing type IV units, receive inhibitory input from I-cells (interneurons), representing type II units. Both sets of model neurons receive a simulated excitatory auditory nerve (AN) input from same-CF AN fibers, where the AN input is modeled as a dead-time modified Poisson process whose intensity is given by a computationally tractable discharge rate versus sound pressure level function. Subthreshold behavior of each model neuron is governed by a set of normalized state equations. The computer mode has previously been shown to reproduce the major response properties of both type IV and type II units (e.g., rate-level curves and peri-stimulus time histograms) and the level-dependence of the functional type II-type IV inhibitory interaction. This model is adapted for the gerbil by simulating a reduced population of I-cells. Simulations were carried out for several auditory nerve input levels, and cross-correlograms were computed from the activities of pairs of P-cells for a complete (cat model) and reduced (gerbil model) population of I-cells. The resultant correlograms show central mounds (CMs), indicative of either shared excitatory or inhibitory input, for both spontaneous and tone-evoked driven activities. Similar to experimental results, CM amplitudes are a non-monotonic function of level and CM widths decrease as a function of level. These results are consistent with the hypothesis that shared excitatory input correlates the spontaneous activities of type IV units adn shared inhibitory input correlates their driven activities. The results also suggest that the decorrelation of the activities of type IV units can result from a reduced effectiveness of the AN input as a function of increasing level. Thus, competition between the excitatory and inhibitory inputs is not required.

Response properties of units in the dorsal cochlear nucleus of unanesthetized decerebrate gerbil

1. The electrophysiological responses of single units in the dorsal cochlear nucleus of unanesthetized decerebrate Mongolian gerbil (Meriones unguiculatus) were recorded. Units were classified according to the response map scheme of Evans and Nelson as modified by Young and Brownell, Young and Voigt, and Shofner and Young. Type II units have a V-shaped excitatory response map similar to typical auditory nerve tuning curves but little or no spontaneous activity (SpAc < 2.5 spikes/s) and little or no response to noise. Type I/III units also have a V-shaped excitatory map and SpAc < 2.5 spikes/s, but have an excitatory response to noise. Type III units have a V-shaped excitatory map with inhibitory sidebands, SpAc > 2.5 spikes/s, and an excitatory response to noise. Type IV-T units typically also have a V-shaped excitatory map with inhibitory sidebands, but have a highly nonmonotonic rate versus level response to best frequency (BF) tones like type IV units, SpAc > 2.5 spikes/s, and an excitatory response to noise. Type IV units have a predominantly inhibitory response map above an island of excitation of BF, SpAc > 2.5 spikes/s, and an excitatory response to noise. We present results for 133 units recorded with glass micropipette electrodes. The purpose of this study was to establish a normative response map data base in this species for ongoing structure/function and correlation studies. 2. The major types of units (type II, type I/III, type III, type IV-T, and type IV) found in decerebrate cat are found in decerebrate gerbil. However, the percentage of type II (7.5%) and type IV (11.3%) units encountered are smaller and the percentage of type III (62.4%) units is larger in decerebrate gerbil than in decerebrate cat. In comparison, Shofner and Young found 18.5% type II units, 30.6% type IV units, and 23.1% type III units using metal electrodes. 3. Two new unit subtypes are described in gerbil: type III-i and type IV-i units. Type III-i units are similar to type III units except that type III-i units are inhibited by low levels of noise and excited by high levels of noise whereas type III units have strictly excitatory responses to noise. Type IV-i units are similar to type IV units except that type IV-i units are excited by low levels of noise and become inhibited by high levels of noise whereas type IV units have strictly excitatory responses to noise. Type III-i units are approximately 30% of the type III population and type IV-i units are approximately 50% of the type IV population. 4. On the basis of the paucity of classic type II units and the reciprocal responses to broadband noise of type III-i and type IV-i units, we postulate that some gerbil type III-i units are the same cell type and have similar synaptic connections as cat type II units. 5. Type II and type I/III units are distinguished from one another on the basis of both their relative noise response, rho, and the normalized slope of the BF tone rate versus level functions beyond the first maximum. Previously, type II units were defined to be those nonspontaneously active units with rho values < 0.3 where rho is defined as the ratio of the maximum noise response minus spontaneous rate to the maximum BF tone response minus spontaneous rate. In the gerbil, the average rho value for type II units is 0.25, although a few values are > 0.3, and the rate-level curves are consistently nonmonotonic with normalized slopes steeper than than -0.007/dB. The average rho value for type I/III units is 0.54, although a few values are < 0.3, and the rate-level curves tend to saturate with slopes shallower than -0.006/dB. In general, the response properties of type II units recorded in gerbil are similar to those recorded in decerebrate cat. 6. In comparison to decerebrate cat, the lower percentage of type IV units recorded in decerebrate gerbil may be due to a species difference (a reduced number of type II units in gerbil) or an electrode bias.

Computed tomography in blunt hepatic trauma

BACKGROUND

Nonoperative management of blunt hepatic injury in hemodynamically stable trauma patients is now common. Recently, it has been proposed that the finding of hepatic periportal tracking (PPT) of blood on the initial computed tomographic (CT) scan is a sensitive marker of significant hepatic and subhepatic injury that might militate against nonoperative management. While CT scan is useful in diagnosing the injury, the utility of follow-up CT scans has not been elucidated.

DESIGN

Retrospective chart review.

SETTING

Regional trauma center.

PATIENTS

The records of 58 hemodynamically stable patients with blunt hepatic trauma were reviewed and the following data recorded: age, outcome, Injury Severity Score (ISS), operative intervention, and complications. Computed tomographic scans were taken on admission and reviewed for the presence of PPT. The timing and radiographic appearance of follow-up CT scans was also recorded.

RESULTS

Seventeen patients (29%) had radiographic evidence of PPT while 41 patients (71%) did not. Age, ISS, injury grade, overall success rate of nonoperative management, and incidence of complications were not statistically significant between the two groups. In no instance did a routine follow-up CT scan affect subsequent management of the patient.

CONCLUSIONS

The finding of PPT on the admission CT scan is not clinically significant and does not preclude nonoperative management of patients with blunt hepatic injury. Furthermore, routine follow-up CT scans are not indicated, as treatment is not influenced by their results. Rather, follow-up CT scans should be obtained as dictated by the patient's clinical course. Extrapolation of these findings to all patients with blunt hepatic trauma in the United States would result in considerable savings of health care dollars, without negatively affecting patient care.

Use of a high affinity DNA ligand in flow cytometry

To investigate the feasibility of using oligonucleotides in flow cytometry we describe a model system consisting of human neutrophil elastase (HNE) coated on 3.3 micro beads and a high affinity DNA ligand for HNE isolated by in vitro selection (SELEX). In this system the fluoresceinated DNA ligand was equally effective as an anti- HNE antibody in detecting HNE on beads. The location on and the chemistry of attachment of fluorescein to the DNA ligand is critical for the sensitivity of detection. DNA constructs in which fluorescein was conjugated via an ethylene glycol tether to either the 5'-end or near the 3'-end gave much higher signals than did probes with fluorescein directly conjugated to either end. Second-step staining with strepavidin-conjugated phycoerythrin was accomplished using a biotinylated DNA ligand in the initial staining of HNE beads. These data suggest that instead of, or in addition to, antibodies high affinity oligonucleotide probes can be useful in diagnostic applications based on flow cytometry.

AIDS nursing care and standardized nursing language: an application of the nursing intervention classification

Standardized nursing language is recommended increasingly as a method to describe the work of nursing, adapt to computerized documentation, and establish a place for nursing in national data bases. Nursing diagnosis has become a standard label for assessment data. The Iowa Interventions Project Research Team proposes that Nursing Interventions Classification (NIC) be adopted to label nursing interventions. The author applies NIC to HIV/AIDS nursing care guidelines from the literature and concludes that NIC can be an important tool as HIV/AIDS nurses develop and describe their knowledge base.

A statistically based method to generate response maps objectively

One scheme to classify the physiological response properties of single units in the cochlear nucleus is based on the average discharge rate of the unit and is reflected in the distribution of excitatory and inhibitory regions in a frequency-level map (response map) that spans the unit's receptive area (e.g., Evans and Nelson, 1973; Young and Brownell, 1976; Young and Voigt, 1982; Shofner and Young, 1985, Spirou and Young, 1991). Typically, discharge rate versus level curves are acquired at many frequencies and the investigator determines that a unit is excited or inhibited at a given level if the driven rate is above or below a spontaneous rate estimate by a specified criterion (for example, 20%). The investigator then encloses regions of excitation and inhibition where responses over adjacent frequencies and levels are consistent. In the present report, we describe an objective 3-step computer-based method to generate response maps: raw driven and spontaneous rate estimates are smoothed with a low-pass spatial filter; a unit is said to be excited or inhibited at a given level if the filtered driven rate is above or below the mean filtered spontaneous rate for that frequency by a specified criterion (percentage or statistical); and resultant response maps are median spatial filtered to eliminate spurious regions. The results shown here demonstrate that use of a statistical criterion provides a more reliable detection of excitation and inhibition than a 20% criterion, particularly when the variance of the rate estimates is high. Further, the statistically based method permits unit classification based on response map data that are more rapidly acquired with shorter duration stimuli (32 vs. 200 ms). Although this method is applied to units recorded in the dorsal cochlear nucleus, the technique may be applicable to studies of receptive fields and their plasticity in other systems.

Malignant degeneration of pilonidal cysts

Malignant degeneration is a rare occurrence in pilonidal disease. The authors present three new cases with a review of the world's previously published 41 cases. Among the total 44 cases, 36 were squamous cell carcinoma. All cases occurred in the setting of long-standing pilonidal disease, with the mean duration of antecedent disease being 23 years. Five of six patients presenting with inguinal metastases died within 16 months. Four patients received adjuvant radiation therapy, one received adjuvant chemotherapy, and one patient in the current series received both adjuvant chemotherapy and radiation. Six patients with recurrence underwent potentially curative resection, with three patients surviving greater than 10 years with no evidence of disease. The authors propose consideration of adjuvant chemotherapy and radiation as a new modality to decrease the local recurrence rate.

Neural modeling of the dorsal cochlear nucleus: cross-correlation analysis of short-duration tone-burst responses

A conceptual model of a portion of dorsal cochlear nucleus (DCN) neural circuitry has emerged over the past two decades. This model suggests that the response properties of the DCN's major projection neurons, called type IV units, are due, in part, to the behavior of local circuit inhibitory interneurons called type II units (Young and Brownell 1976). Cross-correlation studies of simultaneously recorded pairs of DCN units in decerebrate cat derived from 50-s best frequency (BF) stimuli are consistent with and have extended this conceptual model (Voigt and Young 1980, 1985, 1988, 1990). Interestingly, Gochin et al. (1989) found no signs of inhibition in the anesthetized rat DCN in cross-correlograms derived from 55-ms short-duration BF tone bursts. This seemingly contradictory result has motivated this study. Computer simulations were run using our network model of the intrinsic DCN neural circuitry. This model has previously been shown to reproduce the major features of both type II and type IV rate-level curves and the inhibitory trough (IT) observed in cross-correlograms derived from long-duration stimuli (Voigt and Davis 1994). The goal was to study the stimulus-duration-dependent strength of ITs in the cross-correlograms derived from short-duration BF tone-burst stimuli. The results suggest that ITs may not be detectable when the stimulus duration is 50 ms but may be detectable when the stimulus duration is 200 ms or greater. Furthermore, when the ITs are detected in cross-correlograms derived from 200-ms data sets, the strength of the IT, as measured by effectiveness, is comparable to the strength of ITs measured when the stimulus duration is 50 s.