The familial amyotrophic lateral sclerosis-associated amino acid substitutions E100G, G93A, and G93R do not influence the rate of inactivation of copper- and zinc-containing superoxide dismutase by H2O2

Inactivation of copper- and zinc-containing superoxide dismutase (Cu,ZnSOD) by H2O2 is the consequence of several sequential reactions: reduction of the active site Cu(II) to Cu(I) by H2O2; oxidation of the Cu(I) by a second H2O2, thus generating a powerful oxidant, which may be Cu(I)O or Cu(II)OH or Cu(III); and finally oxidation of one of the histidines in the ligand field, causing loss of SOD activity. Three familial amyotrophic lateral sclerosis (FALS)-associated mutant Cu,ZnSODs, i.e., E100G, G93A, and G93R, did not differ from the control enzyme in susceptibility to inactivation by H2O2. It thus appears that an increased peroxidase activity of the FALS-associated Cu,ZnSOD variants might not be a factor in the development of this disease. This leaves the loss of Zn, and the consequent increase in peroxidase activity, or in nitration activity, as a viable explanation (J. P. Crow et al., 1997, J. Neurochem. 69, 1936-1944), among other possibilities.

Structure and expression of the D-amino-acid oxidase gene from the yeast Rhodosporidium toruloides

D-Amino-acid oxidase (DAO2; EC 1.4.3.3) catalyses the oxidative deamination of D-amino acids to alpha-keto acids and ammonia. The purified DAO protein from Rhodosporidium toruloides was used to determine its amino acid sequence. Three internal peptide sequences, YCQYLARELQ, IAGIDDQAAEPIR and RCTMDSSDP, were obtained and used to synthesize four fully degenerated oligonucleotides for cloning of the DAO gene. Both cDNA and genomic DNA encoding R. toruloides DAO were cloned and sequenced. Comparison of these two DNA sequences revealed that the DAO gene contains six exons and five introns. The gene encodes a polypeptide of 368 amino acids with a calculated molecular mass of 40,079 Da. Using an Escherichia coli protein expression system, the DAO protein of R. toruloides can easily be produced in an active form and purified in a large quantity.

Superoxide-dependent peroxidase activity of H48Q: a superoxide dismutase variant associated with familial amyotrophic lateral sclerosis

Approximately 20% of cases of familial amyotrophic lateral sclerosis are caused by dominant mutations in the Cu,Zn superoxide dismutase. One such mutant, in which histidine #48 has been replaced by glutamine (H48Q), exhibits a novel activity. It can react sequentially with O2- and H2O2 to generate a potent oxidant at its active site, possibly Cu(II)-OH, which then can oxidize urate to the corresponding radical. This O2- -dependent peroxidase activity exerted on a substrate peculiar to motor neurons may be the toxic gain of function which leads to the deleterious consequences of this mutation. G93A, G93R, and E100G were also examined and found not to exert this O2- -dependent peroxidase activity.

Conditional oculomotor learning: population vectors in the supplementary eye field

We have shown previously that the activity levels and preferred directions of supplementary eye field neurons change as monkeys learn to associate nonspatial visual information with a saccade (or the spatial target of that saccade). The present report describes changes in neuronal population vectors (PV) during such learning. PVs based on neuronal activity shortly before and after saccades predicted movement direction poorly in the earliest stage of learning, but as monkeys mastered novel stimulus-response mappings, PV accuracy and magnitude increased significantly.

Delivery of recombinant tetanus-superoxide dismutase proteins to central nervous system neurons by retrograde axonal transport

The nontoxic C fragment of tetanus toxin (TC) can transport other proteins from the circulation to central nervous system (CNS) motor neurons. Increased levels of CuZn superoxide dismutase (SOD) are protective in experimental models of stroke and Parkinson's disease, whereas mutations in SOD can cause motor neuron disease. We have linked TC to SOD and purified the active recombinant proteins in both the TC-SOD and SOD-TC orientations. Light microscopic immunohistochemistry and quantitative enzyme-linked immunosorbant assays (ELISA) of mouse brainstem, after intramuscular injection, demonstrate that the fusion proteins undergo retrograde axonal transport and transsynaptic transfer as efficiently as TC alone.

Effects of ozone on normal and potentially sensitive human subjects. Part I: Airway inflammation and responsiveness to ozone in normal and asthmatic subjects

We report here the results of a multiphase project to assess the significance of airway responsiveness and airway injury in ozone (O3)* sensitivity. In Phase I, we measured the preexposure methacholine responsiveness of 66 normal subjects and then exposed these subjects to 0.2 ppm O3 for 4 hours with moderate exercise. Preexposure methacholine responsiveness was weakly correlated with O3-induced increases in specific airway resistance (sRaw) but not O3-induced declines in forced expiratory volume in one second (FEV1) or forced vital capacity (FVC). In addition, O3-induced lower respiratory symptoms were not well correlated with O3-induced changes in lung function. In Phase II, we exposed 23 normal subjects to O3, following an identical protocol to that of Phase I, and then performed bronchoscopy with proximal airway lavage (PAL), bronchoalveolar lavage (BAL), and bronchial biopsy at 18 hours after exposure. Ozone-induced increases in percentage of neutrophils and total protein concentration were observed in both bronchial fraction and BAL fluids; increased percentage of neutrophils also was observed in PAL fluid. These increases were correlated with O3-induced increases in sRaw, but not with O3-induced declines in FEV1 or FVC. Ozone also appeared to increase expression of intercellular adhesion molecule-1, an important mediator of neutrophil recruitment, in bronchial mucosa. In Phase III, we exposed a group of 19 asthmatic subjects to O3, following a protocol identical to that of Phase II. We then compared the lower respiratory symptom and lung function responses of the asthmatic subjects to those of the 81 normal subjects who participated in Phase I, Phase II, or both. The changes in the PAL and BAL fluids of the asthmatic subjects were compared with those of the normal subjects who participated in Phase II. Although both the asthmatic and nonasthmatic subjects showed significant O3-induced changes in lower respiratory symptoms, FEV1, FVC, and sRaw, no significant differences were found between the groups. For sRaw, however, a nonsignificant trend toward a greater O3-induced increase was noted for the asthmatic subjects. In contrast, the O3-induced increases in percentage of neutrophils and total protein concentration in BAL fluid were significantly greater for the asthmatic subjects than for the nonasthmatic subjects. These data suggest that although the lower respiratory symptom and lung function responses to O3 are not markedly greater in asthmatic subjects than in healthy subjects, the inflammatory response of the asthmatic lung may be more intense.

Human stomach alcohol and aldehyde dehydrogenases: comparison of expression pattern and activities in alimentary tract

BACKGROUND & AIMS

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are the major enzymes responsible for ethanol metabolism in humans. The human stomach has been documented to be involved in the metabolism of first-passed alcohol. The aim of this study was to determine ethanol-metabolizing activities in the stomach with regard to sex, age, enzyme pattern, and polymorphism.

METHODS

A total of 209 surgical gastric mucosal specimens were investigated. The expression patterns of ADH and ALDH were identified by isoelectric focusing, and the activities were assayed spectrophotometrically.

RESULTS

At 33 or 500 mmol/L ethanol, pH 7.5, the activities in the ADH3 1-1 phenotypic and mu-ADH-expressing mucosal specimens were significantly greater than that in the ADH3 1-2 phenotypic and mu-ADH absent mucosal specimens, respectively. The activities of the ALDH2-inactive phenotypes were significantly lower than that of the ALDH2-active phenotypes at 200 micromol/L acetaldehyde. The gastric ADH and ALDH activities were not significantly different between men and women with respect to age and genetic polymorphism.

CONCLUSIONS

The stomach may contribute only a small portion of the alcohol metabolism observed in humans, and the liver may be the major site for first-pass metabolism. Differential expression patterns of ADH and ALDH in the alimentary tract suggest that different vulnerabilities to ethanol-induced mucosal injury may exist.

[Clinical and experimental studies on preventing and treating anaphylactic asthma with Zusanli point immunotherapy]

We have studied on preventing and treating anaphylactic asthma with Zusanli (S36) point immunotherapy (ZPIT). Sixty-nine patients were observed. The results showed that the clinical curative effect of ZPIT was not only much higher than that of conventional desensitization therapy, but also the patients' total IgE level was reduced, anti-acarid IgE was lowered, SIgA level was raised, the absolute eosinophilic granulocyte level dropped and pulmonary function recovered. Animal experiment results showed that the ZPIT could more effectively suppress the guinea pigs' anaphylactic asthma allergized by albumin and more obviously resist the guinea pigs' bronchial spasm induced by histamine and acetylcholine than the conventional desensitization therapy and injected normal saline. The immunomodulating action of the ZPIT are elucidated from clinical study and animal experiment in the paper.

Pulmonary complications of HIV infection in Dar es Salaam, Tanzania. Role of bronchoscopy and bronchoalveolar lavage

To determine the pulmonary complications in HIV-1-infected patients in Dar es Salaam, Tanzania, and to evaluate the diagnostic utility of bronchoscopy and bronchoalveolar lavage, we carried out a prospective study of 237 patients with acute respiratory disease who were hospitalized at Muhimbili Medical Center (MMC). Diagnoses were made using well-defined criteria. Of the total, 127 (54%) were HIV-1-seropositive and 110 (46%) were seronegative. Tuberculosis was the most common diagnosis occurring in 95 (75%) HIV-1-seropositive and 87 (79%) seronegative patients. Bacterial pneumonia was the next most common diagnosis occurring in 18 (14%) HIV-1-seropositive and 17 (15%) seronegative patients. Pneumocystis carinii pneumonia was diagnosed in one and Kaposi's sarcoma was seen in only two HIV-1-seropositive patients. Bronchoscopy with bronchoalveolar lavage was the sole source of a diagnosis in nine (8%) seropositive and six (5%) seronegative patients. We conclude that the HIV seroprevalence rate among patients hospitalized for acute respiratory disease at MMC is extremely high. Tuberculosis was the most common cause of pulmonary disease, regardless of HIV serostatus, and other HIV-associated opportunistic pulmonary infections were unusual. Bronchoscopy with bronchoalveolar lavage added little to the diagnosis and thus should not be high-priority procedures for the routine workup in resource-poor areas where tuberculosis is endemic.

Evolution of directional preferences in the supplementary eye field during acquisition of conditional oculomotor associations

We assessed the preferred directions (PDs) of supplementary eye field (SEF) neurons during conditional visuomotor learning. Monkeys learned to select one of four saccadic eye movements in response to a foveal instruction stimulus (IS). ISs were either familiar or novel. Each familiar IS reliably evoked one saccade: 7 degrees left, right, up, or down form the central fixation point. Novel ISs initially triggered virtually random responses among those four possibilities, but the monkeys ultimately learned to select the instructed saccade. As reported previously, activity rates on novel IS trials significantly changed during learning. Some of these cells (learning-dependent) also have significant modulation on familiar IS trials, but others (learning-selective) lack such activity. Of the former, the familiar IS activity can be either directionally selective or omnidirectional. For most neurons, PDs were apparent during all phases of learning, but they were rarely constant. Only infrequently did a neuron's PD for novel ISs closely match that for familiar ISs throughout the learning process. In directional learning-dependent cells, the PD usually reoriented near the end of learning to resemble that for familiar IS trials. In omnidirectional cells, initially evident PDs dissipated with learning, even as the cell became more strongly modulated. Learning-selective cells typically began with significant PDs, but became unmodulated as learning progressed. Our findings show a pervasive lability in SEF PDs that may reflect a flexible and rapid remapping between inputs and responses within the premotor cortical network.

Ozone-induced decrements in FEV1 and FVC do not correlate with measures of inflammation

In order to test the hypothesis that changes in lung function induced by ozone (O3) are correlated with cellular and biochemical indices of respiratory tract injury/inflammation, we exposed 20 healthy subjects, on separate days, to O3 (0.2 ppm) and filtered air for 4 h during exercise. Symptom questionnaires were administered before and after exposure, and pulmonary function tests (FEV1, FVC, and SRaw) were performed before, during, and immediately after each exposure. Fiberoptic bronchoscopy, with isolated left main bronchus proximal airway lavage (PAL) and bronchoalveolar lavage (BAL; bronchial fraction, the first 10 ml of fluid recovered) of the right middle lobe, was performed 18 h after each exposure. The PAL, bronchial fraction, and BAL fluids were analyzed for the following end points: total and differential cell counts, and total protein, fibronectin, interleukin-8 (IL-8), and granulocyte-macrophage colony-stimulating factor (GM-CSF) concentrations. The study population was divided into two groups, least-sensitive (n = 12; mean O3-induced change in FEV1 = -7.0%) and most-sensitive (n = 8; mean O3-induced change in FEV1 = -36.0%). We found a significant O3 effect on SRaw (p<0.001) and lower respiratory symptoms (p<0.001) for all subjects combined, but no significant differences between the least- and most-sensitive groups. Ozone exposure increased significantly percent neutrophils in PAL (p=0.01); percent neutrophils, total protein, and IL-8 in bronchial fraction (p<0.001, p<0.001, and p<0.01, respectively); and percent neutrophils, total protein, fibronectin, and GM-CSF in BAL (p<0.001, p<0.001, p<0.01, p=0.05, respectively) for all subjects combined; there were no significant differences, however, between least- and most-sensitive groups. Our results indicate that levels of O3-induced symptoms and respiratory tract injury/inflammation were not correlated with the magnitude of decrements in FEV1 and FVC.

A receptor kinase-like protein encoded by the rice disease resistance gene, Xa21

The rice Xa21 gene, which confers resistance to Xanthomonas oryzae pv. oryzae race 6, was isolated by positional cloning. Fifty transgenic rice plants carrying the cloned Xa21 gene display high levels of resistance to the pathogen. The sequence of the predicted protein, which carries both a leucine-rich repeat motif and a serine-threonine kinase-like domain, suggests a role in cell surface recognition of a pathogen ligand and subsequent activation of an intracellular defense response. Characterization of Xa21 should facilitate understanding of plant disease resistance and lead to engineered resistance in rice.

Incremental doses of dobutamine induce a biphasic response in dysfunctional left ventricular regions subtending coronary stenoses

BACKGROUND

Dobutamine stress echocardiography has been proposed as a diagnostic tool to identify viable myocardium. How regional wall thickening responds to dobutamine in the ischemic or short-term hibernating myocardium has not been adequately defined. We hypothesized that regional wall thickening would improve initially and subsequently deteriorate with incremental doses of dobutamine in viable myocardial regions supplied by a stenotic coronary artery. This study was undertaken to determine whether this biphasic pattern of regional function characterizes the response of ischemic or hibernating myocardium to dobutamine and to explore the factors and mechanisms that determine this response.

METHODS AND RESULTS

Twenty-six pigs in four groups were studied: a control group (n = 5) to assess the response of myocardium perfused by nonstenotic coronary artery to incremental doses of dobutamine, and three experimental groups with a left anterior descending coronary artery stenosis producing acute myocardial ischemia (n = 7), short-term myocardial hibernation for 90 minutes (n = 7), and short-term hibernation for 24 hours (n = 7) to determine the functional and metabolic response to dobutamine under these conditions. Regional coronary flow was reduced to 40% to 60% of baseline, with significant reductions of regional wall thickening as measured by two-dimensional echocardiography and sonomicrometers. An incremental dobutamine infusion from 2.5 to 25 micrograms.kg-1.min-1 increased wall thickening and coronary flow without lactate production in the control group. In the other three groups, during the incremental dobutamine infusion, regional wall thickening improved initially, from 11.4 +/- 7.5% to 19.8 +/- 11.4%, P < .01, at dobutamine doses of 2.5 to 10 (4.5 +/- 2.2) micrograms.min-1.kg-1 but deteriorated subsequently to 5.0 +/- 5.8% at the maximal dose of dobutamine of 12.6 +/- 4.1 micrograms.min-1.kg-1. The initial improvement of regional wall thickening was associated with a small increase in regional coronary flow (from 0.53 +/- 0.18 to 0.68 +/- 0.25 mL.min-1.g-1 myocardium, P < .05) and with regional lactate production. High doses of dobutamine did not further increase regional coronary flow but markedly increased lactate production and induced regional myocardial acidosis (pH 7.26 +/- 0.07). The biphasic pattern of response to dobutamine was observed in each of the three experimental groups. Both peak improvement and peak deterioration occurred earlier and at lower dobutamine dose levels in the group with acute ischemia compared with the group with short-term hibernation for 24 hours (P < .05).

CONCLUSIONS

A biphasic response of wall thickening to incremental dobutamine with initial improvement and subsequent deterioration is characteristic of ischemic or short-term hibernating myocardium. The initial low-dose dobutamine infusion improved wall thickening in the ischemic or hibernating myocardial region to a modest level. This initial modest improvement was transient and at the expense of metabolic deterioration of myocardial ischemia, so that at higher doses during prolonged dobutamine infusion, wall thickening deteriorated, lactate accumulated, and myocardial acidosis developed.

Increased cellular uptake of the human immunodeficiency virus-1 Tat protein after modification with biotin

The human immunodeficiency virus-1 Tat protein can efficiently enter cells when added exogenously in tissue culture. Using the transactivation activity of Tat as a measure of intracellular delivery, we found that the addition of hydrophobic groups to Tat potentiated its uptake. Biotin was the most promising of the reagents tested and we characterized this effect in more detail. When coupled through a cysteine thiol, the addition of a single biotin to Tat increased activity by about six-fold. Increased activity was only seen with reducible biotin analogs, as modification with noncleavable analogs is known to block Tat transactivation activity. Biotin had no effect on Tat uptake when mixed with Tat without cross-linking. Recently, Tat was used as a carrier to direct the uptake of heterologous proteins into cells. We have used RNase as a model system for studying Tat-mediated uptake and found that biotin also increased the delivery of a Tat37-58-RNase conjugate. The increased uptake of Tat and Tat conjugates by addition of hydrophobic groups may significantly enhance the usefulness of Tat as a delivery vehicle, and the approach may be applicable to other systems.

Cytokine regulation of gelatinase production by head and neck squamous cell carcinoma: the role of tumor necrosis factor-alpha

Gelatinases (GLs) belong to a family of enzymes known as matrix metalloproteinases (MMPs), which are produced by both normal and neoplastic cells. These enzymes have been implicated in tumor invasion and metastasis, although the mechanism of regulation of tumor MMP production is unknown. Since our previous studies have shown that numerous cytokines are present in the tumor microenvironment, our goal was to establish the effect of selected cytokines on GL production by both established tumor cell lines and primary cultures of head and neck squamous cell carcinoma (HNSCC). Supernatants of HNSCC cell lines SCC-25 and FADU stimulated with interleukin (IL)-1 alpha and IL-1 beta demonstrated modest induction of 92 kd GL production by zymogram analysis when compared with controls; IL-2, IL-6, and interferon-gamma had no consistent effect on MMP production. Stimulation of cell lines with tumor necrosis factor (TNF)-alpha (10(4) to 10 U/mL), however, dramatically enhanced production of 92 kd GL by both cell lines in a dose-dependent fashion, although tissue inhibitor of metalloproteinase (TIMP) expression was unaffected. Northern blot analysis showed that this enhancement of 92 kd GL occurred at the messenger RNA level. Stimulation of short-term primary tumor cultures with TNF-alpha resulted in significant enhancement of 92 kd GL expression in one of four cultures and enhancement of 72 kd GL expression in all cultures. The observed increase in GL expression by TNF-alpha suggests a role for this cytokine in the regulation of GL expression by tumor cells during invasion and metastasis.

Neuronal activity in the supplementary eye field during acquisition of conditional oculomotor associations

1. The supplementary eye field (SEF) has been viewed as a premotor cortical field for the selection and control of saccadic eye movements. Drawing on studies of the neighboring premotor cortex, we hypothesized that if the SEF participates in the selection of action based on arbitrary stimulus-response associations, then task-related activity in the SEF should change during the learning of such associations. 2. Rhesus monkeys were operantly conditioned to make a saccadic eye movement to one of four targets (7 deg up, down, left, and right from center) in response to a foveal instruction stimulus (IS). One and only one of those four possible responses was arbitrarily designated "correct" for each IS. The monkeys responded to familiar ISs, four stimuli that remained unchanged throughout training and recording, as well as to novel ISs, which the monkeys had not previously seen. The monkeys initially chose responses to novel stimuli by trial and error, with near chance levels of performance, but quickly learned to select the correct saccade. 3. We studied 186 SEF cells as monkeys learned new visuomotor associations. Neuronal activity was quantified in four task periods: during the presentation of the IS, during an instructed delay period (i.e., after the removal of the IS but before a trigger or "go" stimulus), just before the saccade, and after the saccade during fixation of the target location. The discharge rate in each task period was considered a separate case for analysis, compared with that in a reference period preceding the IS, and eliminated from further analysis if not significantly different. 4. We observed two main categories of activity change during learning, which we termed learning selective and learning dependent. Learning-selective cases showed a significant evolution in activity as the monkeys learned which saccade was instructed by a novel IS, but had no significant modulation during trials with familiar ISs. Many of these cells were virtually inactive on trials with familiar ISs. However, they initially showed dramatic modulation when tested with a novel IS. As the monkey chose the correct saccade (or target) with increasing reliability, the modulation often decremented until the cell was again relatively unmodulated, as observed during familiar-IS trials. These cells usually remained relatively inactive until the monkeys were challenged to start learning another new stimulus-response association. Learning-selective activity was observed in all task periods, and 33 (18%) of the 186 adequately tested SEF cells showed learning-selective activity in one or more task periods.(ABSTRACT TRUNCATED AT 400 WORDS)

Supplementary eye field contrasted with the frontal eye field during acquisition of conditional oculomotor associations

1. The companion paper reported that a substantial proportion of cells in the supplementary eye field (SEF) of macaque monkeys show significant evolution of neuronal activity as subjects learn new and arbitrary stimulus-saccade associations. The purpose of the present study was to compare and contrast the activity of the SEF and the frontal eye field (FEF) during such conditional oculomotor learning. 2. In both SEF and FEF, we observed learning-dependent and learning-selective activity, defined as significant evolution of task-related activity as monkeys learned which of four saccades was instructed by a novel stimulus. By definition, in addition to changes as the monkeys learned the instructional significance of a novel instruction stimulus, learning-dependent activity also showed task-related modulation for trials instructed by familiar stimuli, whereas learning-selective activity did not. Of the 186 SEF neurons adequately tested, 81 (44%) showed one of these two categories of learning-related change. By contrast, of the 90 FEF neurons adequately tested, only 14 (16%) showed similar properties. This difference was highly statistically significant (chi 2 = 21.1; P < 0.001). 3. We also observed persistent differences in activity for trials with familiar versus novel instruction stimuli, which we termed learning-static effects. In some cases, the learning-static effect coexisted with learning-dependent or learning-selective changes in activity, although in others it did not. In the former cases, activity changed systematically during learning, but reached a level that differed from that for familiar stimuli instructing the same saccade. In the latter cases, the activity did not change significantly as the monkey learned new conditional oculomotor associations, but did show a significant difference depending upon whether a novel or familiar stimulus instructed a given saccade. Overall, 66 of 186 (35%) cells in the SEF and 17 of 90 (19%) cells in the FEF showed learning-static effects in one or more task periods. This difference was statistically significant (chi 2 = 7.9; P < 0.005). 4. The significant difference in the properties of SEF and FEF cells suggests a functional dissociation of the two areas during conditional oculomotor learning. In this respect, the FEF resembles the primary motor cortex, whereas the SEF resembles the premotor cortex.

Interleukin-8 expression by head and neck squamous cell carcinoma

OBJECTIVE

To test the hypothesis that interleukin-8 (IL-8) is produced by human head and neck squamous cell carcinomas (HNSCCAs) and may therefore be a possible mediator for lymphocyte recruitment and neovascularization by these tumors.

METHODS

Nine fresh samples of HNSCCA were analyzed for expression of IL-8 antigen using radioimmunoassay and immunohistochemical staining techniques. Also, four short-term primary cultures of HNSCCA and two continuous HNSCCA cell lines were then analyzed for production of IL-8 expression under both baseline conditions and following stimulation with other cytokines.

RESULTS

The IL-8 antigen was detected in all fresh tumor homogenates by radioimmunoassay (5.58 to 331.69 ng of IL-8 per gram of tissue), and immunohistochemical results localized staining predominantly within the tumor cells. Primary cultures of HNSCCA and continuous HNSCCA cell lines produced only low levels of IL-8 (0.04 to 4.49 ng of IL-8 per 10(6) cells) under baseline (unstimulated) conditions. Stimulation of both primary cultures and cell lines with interleukin-1 and tumor necrosis factor induced significant increases in IL-8 antigen, while other cytokines failed to induce a significant increase.

CONCLUSIONS

This study demonstrates that IL-8 antigen is expressed by HNSCCA in vivo, and that cultured HNSCCA in vitro can be stimulated to express IL-8 antigen by both interleukin-1 and tumor necrosis factor. Local production of IL-8 by HNSCCA cells, and its regulation by other cytokines, may be important in both the lymphocyte recruitment and tumor neovascularization seen in HNSCCA, and may thus ultimately affect the natural history of the disease.

Mantle-cell lymphoma in a patient with human immunodeficiency viral infection

Rare cases of low-grade lymphomas have been described in patients with human immunodeficiency virus (HIV) infection. However, this is the first reported case of mantle-cell lymphoma, a type of low-grade lymphoma, in a patient who also had HIV infection. Salient clinical features included lymphocytosis, lymphadenopathy, splenomegaly, and involvement of the bone marrow and meninges. The disease proved to be unusually aggressive and response to chemotherapy was insignificant. The patient survived only 4 months.

Head-direction cells in the rat posterior cortex. I. Anatomical distribution and behavioral modulation

We examined the behavioral modulation of head-directional information processing in neurons of the rat posterior cortices, including the medial prestriate (area Oc2M) and retrosplenial cortex (areas RSA and RSG). Single neurons were recorded in freely moving rats which were trained to perform a spatial working memory task on a radial-arm maze in a cue-controlled room. A dual-light-emitting diode (dual-LED) recording headstage, mounted on the animals' heads, was used to track head position and orientation. Planar modes of motion, such as turns, straight motion, and nonlocomotive states, were categorized using an objective scheme based upon the differential contributions of movement parameters, including linear and angular velocity of the head. Of 662 neurons recorded from the posterior cortices, 41 head-direction (HD) cells were identified based on the criterion of maintained directional bias in the absence of visual cues or in the dark. HD cells constituted 7 of 257 (2.7%) cells recorded in Oc2M, 26 of 311 (8.4%) cells in RSA, and 8 of 94 (8.5%) cells in RSG. Spatial tuning of HD cell firing was modulated by the animal's behaviors in some neurons. The behavioral modulation occurred either at the preferred direction or at all directions. Moreover, the behavioral selectivity was more robust for turns than straight motions, suggesting that the angular movements may significantly contribute to the head-directional processing. These behaviorally selective HD cells were observed most frequently in Oc2M (4/7, 57%), as only 5 of 26 (19%) of RSA cells and none of the RSG cells showed behavioral modulation. These data, taken together with the anatomical evidence for a cascade of projections from Oc2M to RSA and thence to RSG, suggest that there may be a simple association between movement and head-directionality that serves to transform the egocentric movement representation in the neocortex into an allocentric directional representation in the periallocortex.

Patterns of abnormal myogenesis in human cleft palates

To test the hypothesis that soft palate muscles are abnormal in cleft palate, we compared soft palate morphogenesis in fetuses with cleft palate (n = 4) to age-matched (n = 3) and nonmatched (n = 1) control specimens. The morphologic status of all soft palate and masticatory structures were classified into one of six stages based on the level of histogenesis. At 54 mm crown-rump length (CRL), the levator veli palatini (L), palatopharyngeus (PP), and palatoglossus (PG) in cleft subjects demonstrated mesenchymal condensation into myoblastic fields, lagging behind the control specimens (97 mm CRL), which displayed definitive fields of myoblasts and myotube formation. In the 175 mm and 225 mm cleft and the 170 mm and 192 mm control specimens, muscular morphology was similar and had reached its postnatal appearance for the tensor veli palatini (175 m only) and L, PP, PG (225 mm only). Muscle fiber directions were, however, disoriented and disorganized, especially close to the medial epithelial edge of the cleft. The levator veli palatini, could not be distinguished as a discrete muscle in the cleft specimens, and what we believed to be the PP and PG seemed "normal" at the level of light microscopy, but malpositioned in a superior direction. This preliminary study demonstrates for the first time that early myogenesis in cleft palates differs from normal.

Head-direction cells in the rat posterior cortex. II. Contributions of visual and ideothetic information to the directional firing

This study investigated the effects of visual and ideothetic cues on the spatial tuning of head-direction (HD) cells recorded in the rat posterior cortices. Extracellular, single unit responses were recorded from animals performing each of two different tasks, a spatial working memory task on a radial-arm maze and a passive rotation task on a modified "lazy Susan" platform. The influence of visual cues was assessed by manipulating the position of one white and three black cue-cards placed around the maze. We found three major categories of HD cells based on their response to cue manipulations in the maze tasks. Type A cells (10/41) rotated their preferred directions along with the rotation of the cues. The majority (type B, 25/41) of the HD cells were unaffected by the rotation of visual cues, maintaining their established preferred direction. Type C cells (6/41) showed complex responses to cue rotation, with the preferred direction reflecting either a combination of both type A and type B responses or an unpredictable response. The results indicate that the internal representation of directionality can be calibrated by visual cues and that some mnemonic processes may have been involved in the registration of the previous cue locations. Eleven cells were tested in both the maze task and the passive rotation task. Most (9/11) showed a significant directionality in the former task, but showed either no or weak directionality in the latter task, suggesting that movement-related ideothetic cues may be used in supporting the directional firing of these cells. Only two cells showed significant directionality in both tasks. Their established preferred directions did not rotate along with the cues in the maze task, but did rotate with the cues in the passive rotation task. We conclude that the dynamic aspect of the directional tuning in these cortical HD cells may represent on-line calibration of an angular coordinate representation.

[Pharmacological actions of hyphae body of Auricularia auricula (L. ex Hook) Underw and its alcoholic extract]

The percent peripheral blood T lymphocytes were elevated and HC50 reduction induced by cyclophosphamide was recovered after the hyphae body of Auricularia auricula had been ip administered in mice. The action of blood platelet agglutination in rats induced by ADP was inhibited and the time of erythrocytic electrophoresis in mice was shortened after the alcoholic extract had been ig administered.

An accurate impression method for implant prosthesis fabrication

The long-term success of an implant prosthesis depends not only on the development of osseointegration, but also on the maintenance of osseointegration after the prosthetic phase. To achieve this, a passive superstructure must be fabricated. Errors that result from the impression transfer method of implant position during the impression procedures often made it necessary to section and solder metal frameworks repeatedly. This article presents a modified impression technique intended to deal with the problems of more traditional impressions with the aim of achieving a more accurate master cast.

Phospholipid metabolite expression by head and neck squamous cell carcinoma

OBJECTIVE

To characterize the presence and production of various phospholipid metabolites by head and neck squamous cell carcinoma (HNSCC) and squamous cell carcinoma cell lines in vitro and in vivo.

DESIGN

The HNSCC tumor homogenates and supernatants of HNSCC tumor cultures and established squamous cell carcinoma cell lines were assayed for prostaglandin E2 (PGE2), leukotriene B4 (LTB4), and platelet activating factor (PAF). In vitro experiments were carried out under baseline conditions or with exposure to several known immunomodulators (epidermal growth factor, bacterial lipopolysaccharide, and interleukin 1).

PATIENTS

The HNSCC tumor tissue was obtained from primary tumor or cervical lymph node metastasis of surgical resections.

MAIN OUTCOME MEASURES

Prostaglandin E2, LTB4, and PAF were measured in tumor homogenates and cell culture supernatants using standardized radioimmunoassay kits.

RESULTS

All tumor homogenates (eight of eight) contained detectable levels of PGE2 (range, 324 to 2258 pg/g of tumor tissue) and LTB4 (range, 790 to 41,900 pg/g of tumor tissue); PAF was detected in six of eight homogenates (range, 7362 to 40,788 pg/g of tumor tissue). All of the short-term primary HNSCC tumor cultures and squamous carcinoma lines produced PGE2 (range, 90 to 1160 pg/10(6) cells), and half of the cultures produced LTB4 (range, 100 to 1700 pg/10(6) cells); none of the cultures or cell lines produced detectable levels of PAF. Interleukin 1 significantly enhanced production of PGE2 by tumor cultures (P < .02). Characterization of tumor cultures with a fibroblast antibody marker, BR2, revealed that 26% to 64% of tumor culture cells were fibroblasts.

CONCLUSIONS

Prostaglandin E2, LTB4, and PAF are present in the tumor microenvironment, where they may be involved in the local immunosuppression phenomenon seen in HNSCC. Both PGE2 and LTB4 were produced in vitro by tumor cultures and squamous cell carcinoma cell lines; PAF was not produced by tumor cultures in vitro and therefore may be a product of local immune cells in HNSCC in vivo. Interleukin 1 and PGE2 may interact in immunoregulation in the HNSCC tumor microenvironment.

[Studies on the isolation of endogenous sleep factors from Tupaia Belangeri Chinensis (TBC) after sleep deprivation]

The present study was undertaken to explore endogenous sleep factors isolated from 48-72 h sleep deprived (SD) male Tupaia belangeri chinensis (TBC). Only drink ad libitum (10% glucose) was available within 24 h before collection of urine. Controlled "clean" urinary samples were pooled and stored at 20 C. Fraction I-V from the urine were determined after ultrafiltration and Sephadex-G15. Amino-acid analysis of each fraction was automatically done by a 835 Amino-acid Analyzer, respectively. Bioassay was performed in 40 adult rabbits weighing 2.5-3.5 kg of either sex. Experiments were undertaken via the mesodiencephalic intraventricular infusion. Results show that S2C (Fraction-III) (50 micrograms/rabbit, i.c.v.) exhibited significant delta-enhancing effect compared to the controls. Further purification was done with Sephadex G-25 and Sephadex LH-20. The more purified S4B (50 micrograms/rabbit, i.c.v.) also exhibited significant delta-enhancing effect compared to the controls. The amino-acid analysis of Fraction-III revealed that the compositional contents of S2C and S4B are different from what have been known with Factor S, DSIP and SPS.

Tat-mediated delivery of heterologous proteins into cells

The Tat protein of human immunodeficiency virus 1 (HIV-1) can enter cells efficiently when added exogenously in tissue culture. To assess if Tat can carry other molecules into cells, we chemically cross-linked Tat peptides (residues 1-72 or 37-72) to beta-galactosidase, horseradish peroxidase, RNase A, and domain III of Pseudomonas exotoxin A (PE) and monitored uptake colorimetrically or by cytotoxicity. The Tat chimeras were effective on all cell types tested, with staining showing uptake into all cells in each experiment. In mice, treatment with Tat-beta-galactosidase chimeras resulted in delivery to several tissues, with high levels in heart, liver, and spleen, low-to-moderate levels in lung and skeletal muscle, and little or no activity in kidney and brain. The primary target within these tissues was the cells surrounding the blood vessels, suggesting endothelial cells, Kupffer cells, and/or splenic macrophages. Tat-mediated uptake may allow the therapeutic delivery of macromolecules previously thought to be impermeable to living cells.

A sequence-specific single-stranded DNA-binding protein that is responsive to epidermal growth factor recognizes an S1 nuclease-sensitive region in the epidermal growth factor receptor promoter

An epidermal growth factor (EGF) responsive DNA-binding protein (ERDBP-1) has been identified. It recognizes with high affinity and specificity a specific single-stranded DNA sequence located in the S1 nuclease-sensitive site of the EGF receptor (EGFR) 5' flanking region. The EGF-responsive element, determined by footprint analysis, is located from -364 to -344 (86-106 base pairs upstream from the major in vivo transcription initiation site). The factor does not recognize the antisense DNA sequence or double-stranded DNA of the EGF-responsive element. Three bands were observed by mobility shift assay using nuclear extracts from normal human keratinocytes. UV cross-linking followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one major band with molecular weight in the range of 121,000 to 128,000. The induction of ERDBP-1 became evident 3 to 4 h after EGF stimulation and remained elevated as long as EGF was present. HL60 cells are devoid of endogenous EGFR and produce no ERDBP-1. Retroviral gene transfer of EGFR into HL60 cells resulted in induction of ERDBP-1 by EGF to levels comparable to those found in human keratinocytes.

Retroviral gene transfer of epidermal growth factor receptor into HL60 cells results in a partial block of retinoic acid-induced granulocytic differentiation

HL60 cells are devoid of endogenous epidermal growth factor receptor (EGFR). They respond to retinoic acid and undergo terminal granulocytic differentiation. EGFR complementary DNA was introduced into HL60 cells by retroviral gene transfer. Scatchard plot showed that the binding characteristics are identical to those of A431 cells. HL60-EGFR cells were estimated to express 34,000 EGFR/cell (Kd = 5 nM). The tyrosine phosphorylation upon ligand binding is the first step of signal transduction. The dominant phosphotyrosyl proteins in epidermal growth factor-stimulated HL60-EGFR cells include a 170 kDa protein (EGFR itself), and 125 and 53 kDa proteins. The EGFR signal results in the induction of 92 kDa gelatinase/matrix metalloproteinase in HL60-EGFR cells, thereby providing evidence of the function of the exogenous EGFR and a semiquantitative measure of the EGFR signal. These HL60-EGFR cells offer a unique opportunity to examine the potentially important role of EGFR (c-erbB) in maintaining homeostasis between self-renewal and differentiation. c-erbB has been shown to play a physiological role in the self-renewal of the very early avian stem cells which do express EGFR. The v-erbB (double truncated EGFR) has been shown to cause avian erythroblastosis. We found that these HL60-EGFR cells responded to retinoic acid differently from the HL60-control cells. A partial block of only 45% granulocytic differentiation and concomitant proliferation was noted, consistent with a shift of balance between self-renewal and differentiation toward the former.

Pentose phosphate pathway alterations in multi-drug resistant leukemic T-cells: 31P NMR and enzymatic studies

31P NMR studies were carried out on the parental drug-sensitive human T-lymphoblastoid cell line CCRI-CEM (CEM) and its multi-drug-resistant (MDR) CEM-VBL100 variants, to assess the role of the pentose phosphate (PP) in MDR expression. CEM and CEM-VBL100 were incubated in the presence of 2-deoxyglucose, as recently proposed by our group (Clin. Chim. Acta 208: 39, 1992). Accumulation of 2-deoxyglucose 6-phosphate was much lower in the drug-resistant than in sensitive cells, indicating PP shunt activation in the MDR variants. This result was confirmed by enzymatic analyses, which demonstrated that, with respect to the parental line, the MDR variant was characterized by a) unaltered hexokinase activity; b) higher glucose 6-phosphate dehydrogenase activity; c) increased levels of reduced glutathione and marked increase of glutathione peroxidase activity after cell exposure to an oxidizing agent (tert-butylhydroperoxide). These results support the view that cell detoxification mechanisms mediated by the pentose phosphate pathway may contribute to the expression of MDR in tumours.

Altered epidermal growth factor signal transduction in activated Ha-ras-transformed human keratinocytes

Epidermal growth factor (EGF) can stimulate proliferation and 92 kDa gelatinase/matrix metalloproteinase (MMP-9) expression. The induction of MMP-9 is not only pathologically significant for invasion and metastasis, but also serves as a semiquantitative measure of EGF signal transduction. In order to examine the role of mutated ras p21 in EGF signal transduction, an activated Ha-ras-transformed human keratinocyte cell line was developed and characterized. Overexpression of the mutated Ha-ras p21 in these cells was demonstrated. Our results showed that EGF induced 92 kDa MMP-9 secretion was doubled in the ras-transformed keratinocytes in comparison to the parent cells. The karyotype, the expression of EGF receptor (EGFR) and transforming growth factor (TGF) alpha at the mRNA level remained unchanged. These results suggest that the presence of high levels of mutated ras p21 may be responsible for the aberrant EGF signal transduction and contributes to transformation. In addition, a reduction of TGF beta expression at mRNA level by 70% was found in the activated Ha-ras-transformed keratinocytes when compared to the parent cells.

Enflurane inhibits NMDA, AMPA, and kainate-induced currents in Xenopus oocytes expressing mouse and human brain mRNA

Effects of enflurane, an inhalational anesthetic, on NMDA, AMPA, and kainate-gated currents were examined in Xenopus laevis oocytes expressing mouse or human brain mRNA. In oocytes expressing mouse mRNA, enflurane at an anesthetic concentration (1.8 mM) inhibited the NMDA-, AMPA-, and kainate-induced currents by 29-40%, 30-33%, and 20-27%, respectively, suggesting that all three glutamate ionotropic receptors are susceptible to suppression by inhalational anesthetics. Furthermore, inhibition by enflurane was independent of the concentrations of the agonists (NMDA, AMPA, and kainate) or the NMDA-coagonist (glycine). This suggests that enflurane inhibition does not result from a competitive interaction at glutamate or glycine binding sites. Enflurane also suppressed the oscillation and apparent desensitization of NMDA currents, suggesting an inhibition of Ca2+ influx through the NMDA channel. In oocytes expressing human brain mRNA, only kainate produced observable currents. Kainate currents of human channels were smaller in size than those of the mouse; however, the kainate concentration-response curve and percent inhibition (27-29%) by enflurane were similar for mice and humans. The results suggest that human and mouse kainate receptors have similar pharmacological characteristics.

[Efficacy of xiaoxingzhang guttae ophthalmic eye drops in the treatment of experimental herpes simplex keratitis]

The new guttae ophthalmic Xiaoxingzhang (XXZ) was extracted from Radix Actinidiae, a traditional Chinese herbal drug. The 50% inhibition concentration (IC50) of XXZ on type I Herpes Simplex Virus (HSV-1) in virus cell cultures is 165.48-174.73 micrograms/ml. However, XXZ concentrations greater than 400 micrograms/ml did not cause any microscopically visible disruption of vero cells. The efficacy of XXZ in the treatment of experimental Herpes Simplex Keratitis (HSK) in rabbits is higher than that of idoxuridine. The effective doses of XXZ are not toxic to corneal epithelium. The results suggest that XXZ as a new anti-HSV preparation is potentialy useful in the treatment of patients with HSK.

Cytokine expression by head and neck squamous cell carcinomas

Cytokines are known to play an important role in host defense by regulating the function, growth, and differentiation of the cells of the immune system. We hypothesize that, in the tumor microenvironment, tumor cells and resident tissue cells (e.g., fibroblasts) also produce cytokines that may regulate the local immune response to tumors. Initially, homogenates of eight head and neck squamous cell carcinomas (HNSCC) were assayed for the presence of interleukin-1 (IL-1), interleukin-4 (IL-4), interleukin-6 (IL-6), and granulocyte-macrophage colony-stimulating factor (GM-CSF) to establish the presence of these cytokines in the tumors in vivo. We detected IL-1 in all tumor homogenates and IL-4, IL-6, and GM-CSF in some homogenates. To assess the ability of HNSCC to produce these cytokines, supernatants of short-term primary cultures of HNSCC were assayed for the same cytokines. No IL-1 was detected, although baseline levels of IL-4, IL-6, and GM-CSF were present. However, the stimulation of primary tumor cultures with exogenous IL-1 induced or significantly enhanced production of IL-4 (p < 0.01), IL-6 (p < 0.001), and GM-CSF (p < 0.02). These results support our hypothesis that HNSCC secrete cytokines that may influence the response of local immune cells. Our data also suggest that IL-1 may have a central role in regulating the local immune response through the enhancement or induction of cytokine production by tumor and/or resident tissue cells.

General anesthetics potentiate gamma-aminobutyric acid actions on gamma-aminobutyric acidA receptors expressed by Xenopus oocytes: lack of involvement of intracellular calcium

Potentiation of the gamma-aminobutyric acid (GABAA) receptor-gated Cl- channel response has been suggested to be a primary action of some anesthetic agents. We asked whether the GABAA receptor is a target site common for general anesthetics that are chemically and structurally diverse. This hypothesis was tested in Xenopus oocytes expressing mouse cortical mRNA, and GABA-activated Cl- currents were measured using two-electrode voltage clamping. General anesthetics, including inhalational (halothane, diethylether, enflurane and isoflurane), i.v. (3 alpha-hydroxy-5 alpha-dihydroprogesterone, ketamine and propofol) and alcohol (pentanol) anesthetics, enhanced GABA-induced currents by 56 to 1089% at concentrations that were clinically relevant. The results suggest that potentiation of the GABAA receptor/channel response may be a common action for anesthetic agents. Moreover, anesthetic effects were dependent on GABA concentrations; the enhancement was marked with low GABA concentrations and was exponentially decreased as the GABA concentration increased. Also, anesthetic effects were dependent on anesthetic concentrations. The apparent EC50 of halothane was found to be similar to the anesthetic ED50. We also investigated the role of intracellular Ca++ in mediating anesthetic enhancement of the GABA current. We found that intracellular injection of the Ca++ chelator, EGTA, did not change the enhancement by anesthetics. In addition, these anesthetics alone did not produce significant currents, suggesting that the Ca(++)-dependent Cl- current was not activated by these anesthetics per se. Thus, we found that diverse anesthetics potentiate GABA-induced Cl- currents, but this action is not mediated by a release of intracellular Ca++.

Structure/function studies on vascular cell adhesion molecule-1

Vascular cell adhesion molecule-1 (VCAM1) is a member of the immunoglobulin (Ig) superfamily which interacts with the integrin very late antigen-4 (VLA4). The VCAM1/VLA4 interaction mediates both adhesion and signal transduction and is thought to play an important role in inflammatory and immune responses in vivo. The major form of human VCAM1 contains seven extracellular Ig-like domains, with domain 1 designated as the most N-terminal. We have examined the relationship between human VCAM1 structure and function using a combination of domain truncation mutants and proteolytic fragmentation of recombinant soluble VCAM1. We have characterized two regions of VCAM1, localized to domains 4 and 5, which are highly sensitive to proteolytic cleavage, localized the epitope of the blocking monoclonal antibody 4B9 to domain 1, and found that domains 1-3 are sufficient for both its adhesive function and its ability to initiate T cell activation.

Schistosoma mansoni p48 eggshell protein gene: characterization, developmentally regulated expression and comparison to the p14 eggshell protein gene

Egg production by worm pairs is a major cause of pathogenesis in schistosomiasis. To further the understanding of female reproductive development, we have isolated and characterized a complete copy of an eggshell protein precursor gene, p48. Sequence analysis reveals that the gene has 3 open reading frames and does not contain an intron. One of the open reading frames, ORF1, encodes a polypeptide of 50 kDa which shows strong homology to insect chorion proteins. Determination of the position of the mRNA cap-site facilitated identification of putative regulatory elements in the 5' upstream region of the gene. Some of these elements (e.g., TCACGT) have been shown to play a role in the regulation of chorion gene expression in insects. p48 mRNA is detectable only in mature female worms and the ability to detect the mRNA coincides temporally with worm pairing. Quantitative comparisons, during female reproductive development, of p48 transcripts to those from another eggshell protein precursor gene, p14, show that the p48 mRNA is significantly less abundant than p14 mRNA. In mature female worms, p48 mRNA can only be detected in vitelline cells. Antibodies made against the polypeptide sequence deduced from ORF1 of the p48 gene recognize a 50-kDa molecule in extracts from mature female worms, but not in extracts from immature females or males.

Max: functional domains and interaction with c-Myc

The product of the c-myc proto-oncogene is a DNA-binding protein, the deregulated expression of which is associated with a variety of malignant neoplasms. The cDNA for the max gene was recently cloned as a result of the ability of its protein product to interact with the c-Myc protein. We studied bacterially produced Max, c-Myc, and a series of truncated c-Myc proteins. Full-length c-Myc alone cannot bind DNA. However, a truncated c-Myc protein comprising the basic, helix-loop-helix, and leucine zipper regions can bind specifically to DNA bearing the sequence GGGCAC(G/A)TGCCC. Max protein, either alone or in a heteromeric complex with full-length c-Myc, binds to the same core sequence. Using a novel combination of chemical and photo-cross-linking analysis, we demonstrate that either Max or a c-Myc/Max heteromeric complex binds to DNA virtually exclusively in a dimeric structure. Using fusion proteins in cultured cells, we establish a number of functional characteristics of Max. First, we show that Max can interact with c-Myc intracellularly in a manner dependent on the integrity of the helix-loop-helix and leucine zipper motifs. Second, a nuclear localization domain that contains the sequence PQSRKKLR is mapped to the carboxy-terminal region of Max. Third, Max lacks a transcriptional activation domain that is functional in Chinese hamster ovary cells when fused to a heterologous DNA-binding domain. These data suggest that Max may serve as a cofactor for c-Myc in transcriptional activation or, by itself, as a transcriptional repressor.

Identification and characterization of an acyl-CoA:triterpene acyltransferase activity in rabbit and human tissues

Rabbit and human tissues contain substantial amounts of an unusual lipid, a fatty acid ester of a pentacyclic triterpene, that is a potent in vitro inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT). A possible origin of the triterpene ester is via dietary absorption of plant triterpenes (which have a similar structure to the triterpene moiety of the animal triterpene ester), followed by fatty acid esterification of the triterpene in animal tissues. To support this idea, homogenates of rabbit and human enterocytes and liver are now shown to contain an acyl-CoA:triterpene acyltransferase activity (ATAT) which esterifies triterpene to a fatty acid. The enzyme activity was stimulated by exogenous triterpene and required ATP and coenzyme A when fatty acid was used as substrate; ATP and coenzyme A were not required when fatty acyl-CoA was used. ATAT was not inhibited by two structurally different ACAT inhibitors, which may indicate that ACAT and ATAT are different enzymes. Rat enterocytes and liver contained very little ATAT activity, consistent with the finding that rat liver contained very little triterpene ester. To establish that triterpene esterification occurs in vivo, [3H]triterpene was shown to be incorporated into triterpene ester in several organs and tissues from a rabbit given a gastric bolus of the labeled triterpene. These data provide support for the hypothesis that triterpene esters in animal tissues arise from the dietary absorption of triterpenes followed by the esterification of the triterpenes by an enzymatic activity in the animal tissues.

The increased potency of cross-linked lymphocyte function-associated antigen-3 (LFA-3) multimers is a direct consequence of changes in valency

We have used chemically cross-linked dimers, trimers, and tetramers of lymphocyte function-associated antigen-3 (LFA-3) to study the role of multivalency in the interaction of the protein with its receptor, CD2. The cross-linked adducts showed enhanced activity in systems where LFA-3 has been shown to (i) block LFA-3/CD2 interactions in a rosetting assay and (ii) provide through the CD2 on peripheral blood lymphocytes a trigger for T-cell proliferation. The level of increase was directly related to the valency state of the multimers. In the rosetting assay, the dimers, trimers, and tetramers, by weight, exhibited 15-, 150-, and 430-fold increases in activity over monomeric LFA-3. In the proliferation assay, the tetramer produced a 6-fold increase in thymidine incorporation at 0.06 micrograms/ml, the trimer was 100 times less active than the tetramer, and the dimer and monomer were inactive. The LFA-3 multimers were generated using a three-step cross-linking chemistry that was targeted at the carbohydrates on LFA-3. With this procedure over 60% of the starting protein was converted into multimers with no effect on function. The cross-linking approach should be applicable to other surface antigens, providing a simple method for analyzing multivalent interactions.

Production of multimeric forms of CD4 through a sugar-based cross-linking strategy

We have developed a three-step cross-linking procedure that is specifically targeted at the carbohydrate on a protein and applied it to CD4 as a model system for studying the role of multivalent interactions in function. In the first step CD4 was oxidized with periodate, creating aldehydes that served as targets for the subsequent chemistry. Next the aldehydes were modified with cystamine, converting the reactive group into a thiol. Finally cross-linking through the thiol moiety was generated with the homobifunctional cross-linker bismaleimidohexane. With this procedure, approximately 60% of the CD4 was converted into higher molecular weight complexes that were soluble and retained function as assessed by glycoprotein gp120 binding activity. CD4 dimers and tetramers by mass were 4 and 15 times as active as CD4 monomer in blocking virus infection with HTLV-IIIB in an in vitro cellular assay. The cross-linking chemistry provides an efficient method for producing homomultimers of a glycoprotein.

The remodeling of synaptic extracellular matrix and its dynamic relationship with nerve terminals at living frog neuromuscular junctions

The question of whether the synaptic extracellular matrix undergoes remodeling and how this remodeling is related to nerve terminal plasticity was examined in living neuromuscular junctions of adult frogs. Sartorius muscles were double stained with a fluorescent nerve terminal dye 4-(4-diethylamino-styryl)-N-methylpyridinium iodide (4-Di-2-Asp) and rhodamine-tagged peanut agglutinin (PNA) which recognizes synaptic extracellular matrix. Both nerve terminals and synaptic extracellular matrix in 200 identified normal junctions were visualized in vivo two or three times over a period of 2.6-6 months. The majority of neuromuscular junctions (NMJs) showed remodeling of both nerve terminals and synaptic extracellular matrix. Only 2.5% showed no changes in either synaptic element. The most commonly seen remodeling involved correlated changes in both nerve terminals and synaptic extracellular matrix. In this large group, while some junctions (20%) showed overall proportionate changes in all branches, most junctions (68%) showed disproportionate extension and/or retraction of some but not all individual branches. Another group of NMJs (9.5%) showed mismatched changes in the nerve terminal and synaptic extracellular matrix. In this group, some NMJs showed a decrease in the nerve terminal length without a corresponding reduction in synaptic extracellular matrix length. In other junctions that displayed extension of branches, the PNA-stained matrix was longer than the distal tip of the nerve terminal. Morphometric analysis indicated an average increase of 15.6% in total nerve terminal length and 13.6% in total synaptic extracellular matrix length. Although almost all NMJs displayed remodeling in at least one branch, about 50% of the 2201 individual branches examined did not show changes. The average change was 8.9% growth in the length of individual nerve terminal branches and 8.3% growth in the length of individual branches of synaptic extracellular matrix. There was no significant difference in the morphometry between the repeatedly observed junctions and the previously unobserved control junctions. Furthermore, junctions in which the synaptic extracellular matrix was longer than the nerve terminal also were seen in control as well as in experimental muscles. Cases where the nerve terminals were longer than the synaptic extracellular matrix were never observed in newly arising junctional branches. The present study has shown extensive remodeling in not only the nerve terminal but also the synaptic extracellular matrix in adult living frog NMJs. Results suggest that nerve terminals retract before the synaptic extracellular matrix. A hypothesis that extension of synaptic extracellular matrix precedes nerve terminal growth during synaptic remodeling is proposed.

“Dead Reckoning,” Landmark Learning, and the Sense of Direction: A Neurophysiological and Computational Hypothesis

Behavioral and neurophysiological evidence strongly suggests that, within certain limits, rodents and humans can keep track of their directional heading relative to an inertial, and hence allocentric coordinate system. This “sense of direction” appears to involve the integration of angular velocity signals that arise primarily in the vestibular system. A hypothesis is proposed in which the integration process, an operation that may be difficult for neurons to implement, is replaced by a linear associative mapping, an operation that is at least theoretically easy to implement with neurons. The proposed system makes use of a set of linearly independent vectors representing the combination of the current head direction, and head angular velocity representations to “recall” the resulting head direction. It is then proposed that visual landmarks become incorporated into the directional system, enabling both the correction of cumulative error and, ultimately, the computation of novel, optimal trajectories between locations. According to the hypothesis, this occurs through the association of hippo-campal “local-view” cells (i.e., direction selective “place cells”) with “head-direction” cells located downstream in the dorsal presubiculum. The possible neurophysiological and neuroan-atomical bases for the proposed system are discussed.