Expression and functional significance of an additional ligand for CTLA-4

Effective T-cell activation requires antigen/major histocompatibility complex engagement by the T-cell receptor complex in concert with one or more costimulatory molecules. Recent studies have suggested that the B7 molecule, expressed on most antigen presenting cells, functions as a costimulatory molecule through its interaction with CD28 on T cells. Blocking the CD28/B7 interaction with CTLA4Ig inhibits T-cell activation in vitro and induces unresponsiveness. We demonstrate that another molecule(s), termed B7-2, is expressed constitutively on dendritic cells, is differentially regulated on B cells, and costimulates naive T cells responding to alloantigen. B7-2 is up-regulated by lipopolysaccharide in < 6 hr and is maximally expressed on the majority of B cells by 24 hr. In contrast, B7 is detected only on a subset of activated B cells late (48 hr) after stimulation. In addition, Con A directly induces B7-2 but not B7 expression on B cells. Finally, although both anti-B7 monoclonal antibodies and CTLA4Ig blocked T-cell proliferation to antigen-expressing B7 transfectants, only CTLA4Ig had any significant inhibitory effect on T-cell proliferation to antigens expressed on natural antigen presenting cells, such as dendritic cells. Thus, B7 is not the only costimulatory molecule capable of initiating T-cell responses since a second ligand, B7-2, can provide a necessary second signal for T-cell activation.

GTP binding and hydrolysis by the signal recognition particle during initiation of protein translocation

The signal recognition particle (SRP) consists of one RNA and six protein subunits. The N-terminal domain of the 54K subunit contains a putative GTP-binding site, whereas the C-terminal domain binds signal sequences and SRP RNA. Binding of SRP to the signal sequence as it emerges from the ribosome creates a cytosolic targeting complex containing the nascent polypeptide chain, the translating ribosome, and SRP. This complex is directed to the endoplasmic reticulum membrane as a result of its interaction with the SRP receptor, a membrane protein composed of two subunits, SR alpha and SR beta, each of which also contains a GTP-binding domain. In the presence of GTP, SRP receptor binding to SRP causes the latter to dissociate from both the signal sequence and the ribosome. GTP is then hydrolysed so that SRP can be released from the SRP receptor and returned to the cytosol. Here we show that the 54K subunit (M(r) 54,000) of SRP (SRP54) is a GTP-binding protein stabilized in a nucleotide-free state by signal sequences, and that the SRP receptor both increases the affinity of SRP54 for GTP and activates its GTPase. We propose that nucleotide-mediated conformational changes in SRP54 regulate the release of signal sequences and the docking of ribosomes at the endoplasmic reticulum.

Preoperative prediction for the use of cardiopulmonary bypass in lung transplantation

Cardiopulmonary bypass has been widely used in the management of isolated single and double lung transplantations. Although there are certain clear-cut preoperative indications for cardiopulmonary bypass, in many patients the decision to use this modality is based on the hemodynamic consequences of intraoperative pulmonary artery clamping. We have performed 109 isolated lung transplantations. In 69 patients (38 single lung transplantations and 31 double lung transplantations) cardiopulmonary bypass was initiated only on the basis of intraoperative hemodynamics. We have analyzed preoperative data from these 69 patients to determine whether an intraoperative requirement for cardiopulmonary bypass can be predicted. Of 38 single lung transplantations, 12 necessitated cardiopulmonary bypass (all patients had restrictive lung disease). No patients with obstructive lung disease who underwent single lung transplantation required cardiopulmonary bypass (p < 0.001). For single lung transplantations, 6-minute walk, the arterial desaturation/oxygen requirements on exercise, and the right ventricular ejection fraction were all significantly different between the cardiopulmonary bypass and noncardiopulmonary bypass groups (p < 0.001). Of 31 double lung transplantations, 10 patients required cardiopulmonary bypass (seven had bronchiectasis, two had obstructive lung disease, and one had restrictive lung disease). For obstructive lung disease, no preoperative parameters predicted cardiopulmonary bypass. In conclusion, cardiopulmonary bypass is not necessary for most patients undergoing lung transplantation (in the absence of an absolute preoperative indication). Obstructive lung disease rarely necessitates cardiopulmonary bypass. In single lung transplantations, the subsequent requirement for cardiopulmonary bypass can be predicted from preoperative cardiopulmonary performance. For double lung transplantations, the requirement for cardiopulmonary bypass is usually dependent on unpredictable intraoperative factors.

Pediatric retransplantation

Previous studies have attempted to outline the efficacy of heart retransplantation in adults. A limited number of these retransplantation procedures have been performed in children; however, no study to date has evaluated the risk of heart retransplantation in this specific patient population. We conducted a retrospective review of 17 pediatric (non-neonatal) heart transplant recipients who subsequently underwent heart retransplantation. Thirteen male and four female patients underwent retransplantation at four different institutions between 1974 and 1992. Patient age at the time of primary transplantation ranged from 2 to 19 years (mean, 12.5 years) and from 3 to 30 years (mean, 16 years) at retransplantation. The time interval between transplantation procedures ranged from 2 days to 15.6 years and was not predictive of patient outcome. Follow-up after retransplantation ranged from 1 day to 11 years (mean, 2.8 years). All patients were New York Heart Association class 3 or class 4 at the time of retransplantation. After retransplantation all survivors were New York Heart Association class 1. No patient had mechanical device implantation or extracorporeal membrane oxygenation bridge-to-transplantation at primary transplantation or retransplantation. The indication for retransplantation was transplant coronary artery disease (TxCAD) in seven patients (41.2%), acute rejection in four (23.5%), chronic rejection in one (5.8%), chronic rejection associated with TxCAD in four (23.5%), and intraoperative donor organ failure in one (5.8%). No significant difference occurred in linearized rates of rejection or infection or in actuarial freedom from rejection or infection when secondary grafts were compared with primary grafts in patients undergoing retransplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the Glasgow Coma Scale and the Swedish Reaction Level Scale

The Glasgow Coma Scale (GCS) and the Swedish Reaction Level Scale (RLS85), two level-of-consciousness scales used in the assessment of patients with head injury, were compared in a prospective study of 239 patients admitted to a regional head injury unit over a 4-month period. Assessments were made by nine staff members ranging from house officer to registrar, after briefing about the two scales. Data were also collected on age, nature of injuries, surgical treatment, and condition at discharge or transfer using the Glasgow Outcome Scale. Both the GCS and the RLS85 reliably identified comatose patients and those with minor head injury, but were much less effective in defining the response level in patients considered to have a moderate head injury. Only 41% of the patients allocated to a moderate-head-injury category by the GCS and the RLS85 were common to both groups. Where a mismatch occurred, neither scale allocated patients to a 'better' or 'worse' category more frequently than the other. Assessment of patients' conscious levels using the GCS was difficult in only two cases. One patient had facial injuries, and the other was intubated. The RLS85 was reported by all users to be simpler to use than the GCS, but the latter is much more widespread in use. Both scales function well in cases of severe and minor head injury, but have weaknesses when defining moderate head injury. Level-of-consciousness scales are only an aid to assessment and the final choice between the two scales must remain a matter of personal or departmental preference.

The fragmentation of 670A MeV neon-20 as a function of depth in water. III. Analytical multigeneration transport theory

This is the final report of a detailed study of the interaction of 670A MeV neon ions with water, used as a presumed tissue-equivalent target. A first comparison of the data with theoretical fluence spectra predicted by the one-generation heavy-ion transport code HZESEC was reported previously. In the present article, subsequent nuclear interactions of the fragment are taken into account, using the LBLBEAM multigeneration heavy-ion transport code, which incorporated new features and modifications intended to address some of the approximations made in the previous calculation. The LBLBEAM code uses the method of characteristics and an iterative procedure to solve a one-dimensional Boltzmann transport equation for the first through third successive generations of nuclear reaction products; it includes a recent version of the semiempirical model used to derive nuclear interaction cross sections. The stopping power used for the theory was calculated in the same way that experimental time-of-flight and energy-loss data are converted to obtain a comparison independent of stopping power; accordingly, good agreement was found between calculated and measured neon fluence spectra in the Bragg peak region. Multiple scattering effects were considered separately for each isotope in the present work. Acceptance factors were calculated as previously, assuming that all projectile fragments originate from the first nuclear interaction. The results show that lower-mass isotopes can account for the high-LET portions of the spectrum in measured fluence spectra. Third-generation products become increasingly important as a source of lighter fragments for depths comparable with the primary particle mean free path, accounting for between one-third and one-half of carbon and lighter particles near the Bragg peak; higher-order interactions were negligible for the detector geometry and material thicknesses examined. Agreement between measured and calculated fluence spectra is 30% (20% for integral fluences). Inclusion of hydrogen, helium, and lithium fragments improves agreement between calculated and measured RBE values for spermatogonial cell survival, but tertiary particle acceptance and track structure effects need to be understood in greater detail to predict RBE accurately.

A queue-series model for reaction time, with discrete-stage and continuous-flow models as special cases

This article presents a new reaction time model that includes both sequential-stage (discrete) and overlapping-stage (continuous-flow) models as special cases. In the new model, task performance is carried out by a series of distinct processing stages, each of which functions as a queue. A stimulus conveys 1 or more distinct components of information (e.g., features), and each stage can begin processing as soon as it receives 1 component from its predecessor. If a stimulus activates only 1 component, successive stages operate in strict sequence; if it activates multiple components, successive stages operate with temporal overlap. Within this class of models, experimental factors affecting different processing stages always have additive effects on reaction time with sequential stages but rarely do so with overlapping stages. Within this class of models, then, observations of factor additivity support discrete-stage models.

Transoral-transpharyngeal approach to the upper cervical vertebrae

The classical operative approaches to the cervical spine include the posterior one and the anterior exposure along the sternomastoid muscle. However, neither of these are helpful in exposing the upper cervical vertebrae, especially the odontoid process, atlas, and axis. We have used the transoral-transpharyngeal exposure for lesions of the odontoid process and upper (first to third) cervical vertebrae in six patients. The pathologic processes included rheumatoid disease and fracture of the cervical vertebrae, suspected tumor with compression of the spinal cord, basilar invagination, and compression of the medulla. In all six patients, the exposure was excellent, and postoperative morbidity was minimal. Tracheostomy was performed routinely in all these patients. In five patients, vertebral stabilization was performed as a secondary procedure a few days after the initial anterior decompressive surgery. The transoral-transpharyngeal approach appears to be relatively easy. It is associated with minimal complications and provides excellent exposure of the odontoid and upper cervical vertebrae for a microneurosurgical approach. Modifications of this approach include incision of the soft palate, excision of a portion of the hard palate, and, occasionally, transmandibular median labio-mandibulo-glossotomy (Trotter's) approach. Although the technique was described initially approximately 35 years ago, this neglected anatomic approach will facilitate cooperative efforts between head and neck surgeons and neurosurgeons.

Chronic myelogenous leukemia: in search of the benign hematopoietic stem cell

Donor marrow transplantation can cure chronic myelogenous leukemia (CML). Unfortunately, the procedure is associated with severe complications and is limited to the minority of potential recipients with suitably matched donors. Autologous marrow transplantation using negative selection approaches such as incubation with gamma interferon (IFN-gamma) can produce cytogenetic and clinical remissions, but they are often associated with recurrent evidence of leukemia. A primitive progenitor population can be separated from normal human marrow on the basis of morphologic characteristics and cell surface antigen expression. Cell populations with similar morphologic and phenotypic characteristics obtained by positive selection from the marrow of patients with CML appear to be benign. Benign primitive and committed progenitors selected in this fashion can be expanded ex vivo when cultured in a "Transwell" system which physically separates hematopoietic cells from stromal feeder layers. Positive selection and ex vivo cultivation of benign progenitors from CML marrow may provide a source of hematopoietic stem cells suitable for autologous marrow transplantation. Autologous natural killer (NK) cells obtained from the peripheral blood of patients with CML are of benign origin and have antileukemia activity. Interleukin 2 (IL-2) activated autologous NK cells may be used in post-transplant cellular therapy to prevent recurrence of CML.

Brain-derived neurotrophic factor (BDNF) prevents the degeneration of medial septal cholinergic neurons following fimbria transection

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, supports the survival of developing basal forebrain cholinergic neurons in vitro and is retrogradely transported by cholinergic neurons of the medial septum and diagonal band following intrahippocampal injections in vivo. To substantiate a potential role for BDNF in the maintenance of forebrain cholinergic neurons in the adult brain, we assessed the ability of BDNF to sustain the phenotype of medial septal cholinergic neurons following a unilateral transection of the fimbria. BDNF, NGF, or vehicle solutions were infused continuously in adult female rats either into the lateral ventricle (intracerebroventricularly) or directly into the septum for 2 weeks beginning at the time of the transection. In vehicle-infused animals, only 28% of the ChAT-immunoreactive neurons remained on the side ipsilateral to the lesion compared to the contralateral intact side. When infused intracerebroventricularly, both BDNF and NGF reduced the extent of the phenotypic loss, in that 44% and 68%, respectively, of the ChAT-immunopositive neurons remained on the lesioned side. Intraseptal infusion proved even more effective, in that following BDNF and NGF treatment 60% and 86%, respectively, of the normal complement of ChAT-immunopositive neurons were apparent on the side ipsilateral to the lesion. Similar results were obtained when an antibody to the low-affinity NGF receptor was used to identify the cholinergic neurons. To determine if the apparent greater efficacy of NGF compared to BDNF might be related to differences in delivery, we examined the patterns of distribution of radiolabeled BDNF and NGF injected into the lateral ventricle. 125I-BDNF showed only very little diffusion from the ventricles into the adjacent neural tissue and negligible retrograde labeling of the neurons within the basal forebrain. 125I-NGF, however, diffused readily into the brain, resulting in widespread retrograde labeling of basal forebrain neurons. A similarly limited distribution pattern was observed where BDNF was detected immunohistochemically in animals infused intracerebroventricularly (12 micrograms/d) for 2 weeks. In contrast, when delivered intraseptally, the same dose of BDNF exhibited a widespread diffusion within the surrounding neuropil and retrograde labeling of neurons in the medial septum and the vertical limb of the diagonal band. Thus, when delivered effectively, BDNF has a substantial capacity to rescue axotomized cholinergic neurons.

Vancomycin skin tests and prediction of "red man syndrome" in healthy volunteers

The purpose of the present study was to assess the cutaneous response to intradermally administered vancomycin in healthy adults and to determine whether the magnitude of the cutaneous response correlated to the severity of "red man syndrome" (RMS) following intravenous administration of vancomycin to the same subjects. Eleven healthy males were skin tested with intradermally administered histamine and saline controls and intradermally administered vancomycin at different concentrations. Vancomycin caused a dose-dependent area of flare in all subjects. The sigmoidal maximal flare model was used to fit each dose-response curve, and cutaneous responsiveness to vancomycin was quantified by various methods, including the flare area at each dose, maximum flare area (maximal flare), dose required to produce 50% of maximum flare, dose required to produce a flare area of 400 mm2, and the slope of the dose-response curve. One week after skin testing, subjects received an infusion of vancomycin, 15 mg/kg of body weight over 60 min. For the assessment of the severity of RMS, we used previously described methods. Although all subjects experienced erythema from the intravenously administered vancomycin and 10 subjects had pruritus, there was no significant correlation between vancomycin skin test results and the severity of RMS. We conclude that vancomycin skin tests do not predict the severity of RMS. In addition, vancomycin skin tests may be of no benefit for assessing immunoglobulin E-mediated allergy to vancomycin, since all subjects had a positive reaction at concentrations of > or = 10 micrograms/ml.

Neuropathological and neurophysiological effects of interstitial white matter autologous and non-autologous protein containing solutions: further evidence for a glioma derived permeability factor

The feline infusion model of brain edema was used to evaluate the pathophysiological effects of 0.6 ml infusions of autologous serum protein (66%), human serum protein (66%), human glioma cyst fluid and a tissue culture medium (TCM) on the structure and function of the forebrain white matter. These infusions increased local white matter water content by between 10.8 and 12.5 ml/100 g brain and were associated with moderate increases in ICP and CSF outflow resistance and a significant decrease in lumped craniospinal compliance. Cortical somatosensory potentials, motor evoked potentials, EEG and local cerebral blood flow (rCBF) at normocapnia were generally unchanged by the various infusions. All infusates except the 66% autologous serum protein infusion impaired rCBF CO2 reactivity. Histologically all infusates caused marked extracellular edema. The autologous serum protein infusion caused no additional histological changes whereas the glioma cyst infusates caused profound endothelial and astrocytic swelling, focal endothelial necrosis, basement membrane disruption, perivascular microglial reaction and pavementation and perivascular migration of polymorphonuclear leukocytes. Similar but less marked changes were seen after infusion of human serum protein whilst the TCM produced only minimal changes. The intensity and extent of Evans Blue extravasation into the forebrain white matter was greatest with glioma cyst infusates and with all infusions reflected the extent to microvascular changes. These studies show that products derived from gliomas cause additional damage to the blood-brain-barrier than that caused by non-autologous serum proteins. These results add further support for the existence of glioma derived permeability factors (GDPF), but suggest neither serum proteins nor glioma derived compounds in the white matter interstitium significantly influence local electrophysiological function. Some limitations of the infusion edema model when using non-autologous infusions and difficulties quantitating brain dysfunction are emphasised.

A novel adenylyl cyclase-activating serotonin receptor (5-HT7) implicated in the regulation of mammalian circadian rhythms

We report the cloning and characterization of a novel serotonin receptor, designated as 5-HT7, which is coupled to the stimulation of adenylyl cyclase. 5-HT7 mRNA is expressed discretely throughout the CNS, predominantly in the thalamus and hypothalamus. 5-HT7 has a unique pharmacological profile that redefines agonist and antagonist classification of ligands previously thought to be "selective." The circadian phase of spontaneous neuronal activity of the rat suprachiasmatic nucleus of the hypothalamus advances in response to serotonin ligands with a pharmacological profile consistent exclusively with that of 5-HT7. These findings suggest a physiological role in the regulation of circadian rhythms for one subtype of serotonin receptor, 5-HT7, and provide a pharmacological test to evaluate its role in other neuronal systems.

Necrobiotic xanthogranuloma without periorbital lesions

Cutaneous necrobiotic xanthogranuloma is rare and closely resembles widespread necrobiosis lipoidica. It is important to recognize this skin disorder because of its strong association with paraproteinemia and, in some cases, with a hematologic malignancy. We describe two patients with necrobiotic xanthogranuloma who are unusual in that they had no periorbital involvement, a feature previously believed to be diagnostic of this condition.

Laparoscopic cholecystectomy in patients admitted with acute biliary symptoms

Laparoscopic cholecystectomy has become the standard of care for the elective management of cholelithiasis. Little information exists, however, regarding the appropriateness of this procedure in the setting of acute symptomatology. We retrospectively reviewed our experience with 516 laparoscopic cholecystectomies performed at a single institution from May 1990 to May 1991. Seventy-five (14.5%) of these patients were admitted from the emergency department with acute abdominal pain (100%), fever (4 of 75, 5%), and/or an elevated white blood cell count (22 of 75, 29%). There were 54 females and 21 males, with a mean age of 50.0 +/- 2.4 years (range: 17 to 89 years). Laparoscopic cholecystectomy was attempted in all patients, and was successful in 68 of 75 patients (91%). Seven procedures were converted to open cholecystectomy because of the difficulty in dissection precluding safe laparoscopic cholecystectomy. The time from admission to surgery (mean: 3.4 +/- 0.3 days), as well as the total hospital stay (mean: 5.5 +/- 0.6 days), was much longer than in the elective circumstance. Mean laboratory values for the group as a whole were as follows: white blood cell count (mean: 9.6 IU/L +/- 0.4 IU/L, range: 4.1 IU/L to 19.5 IU/L), alkaline phosphatase (mean: 97.0 IU/L +/- 13.7 IU/L, range: 27 IU/L to 375 IU/L), and alanine aminotransferase (mean: 78.3 IU/L +/- 13.7 IU/L, range: 15 IU/L to 701 IU/L). Patients requiring open cholecystectomy were older (mean: 61.4 +/- 4.4 versus 48.8 +/- 2.6), were more likely to be febrile (3 of 7, 42%, versus 1 of 68, 1%), and were more likely to have a significant leukocytosis (mean: white blood cell count 12.9 +/- 1.8 x 10(3) cells/mm3 versus 9.2 +/- 0.4 x 10(3) cells/mm3) than were those undergoing successful laparoscopic cholecystectomy. Laparoscopic cholecystectomy can be performed safely in the majority of patients presenting with acute biliary symptoms. Patients with a triad of acute abdominal pain, fever, and elevated white blood cell count, particularly elderly patients, are more likely to require conversion to open cholecystectomy, however.