Partial purification and characterization of a 235,000M(r) extracellular proteinase from Trichophyton rubrum

An extracellular proteinase has been partially purified from culture filtrates of Trichophyton rubrum by ultrafiltration, isoelectric focusing and gel filtration chromatography. The enzyme has a non-reduced molecular weight of 235,000 by substrate SDS-PAGE. It has a pH optimum of 8.5 using azocasein and azoalbumin as substrates and a pI of 3.6-3.8. The metalloproteinase inhibitors EDTA and 1,10-phenanthroline, together with the chymotrypsin inhibitor chymostatin, strongly inhibited its activity. The serine proteinase inhibitors phenylmethanesulphonyl fluoride and diisopropylfluorophosphate showed weak inhibitory activity. The proteinase exhibited broad substrate activity against azocoll, azoalbumin, azocasein, laminin and fibronectin. It exhibited weak activity against elastin and keratin. Observations on the occurrence of this proteinase together with previously described lower molecular weight proteinases suggests that the former is the first to appear in minimal medium cultures. Freeze/thaw cycling of the partially purified 235,000 M(r) proteinase was found to generate low molecular weight proteinases, particularly at 53,000, 27,000 and 25,000 M(r), indicating that the latter may originate from the larger molecule.

Purification of the 115-kilodalton exoantigen of Cryptococcus neoformans and its recognition by immune sera

A 115-kDa exoantigen produced by Cryptococcus neoformans recognized by the previously described murine monoclonal antibody 7C9 has been purified from culture filtrate by a combination of membrane ultrafiltration, isoelectric focusing, and preparative gel electrophoresis. It is produced in late-log-phase cultures and is present in greater amounts in cultures grown at 25 degrees C than in those grown at 37 degrees C. Recognition of the antigen by 7C9 on immunoblots is abolished by the proteolytic enzymes papain and trypsin. The antigen is a glycoprotein bearing N-linked oligosaccharides, of which mannose is an important constituent. It does not appear to have proteolytic activity and is acidic, with a pI of 3 to 3.2. Its relationship to previously described C. neoformans mannoprotein is unclear since 7C9 shows only very weak cross-reactivity with a purified sample of the latter. Sera from patients infected with C. neoformans exhibited strong recognition of the glycoprotein as shown by immunoenzyme development of Western immunoblots, indicating its possible significance as a marker of disease.

Possible mechanisms of immune modulation in chronic dermatophytoses: an in vitro study

It has been suggested that patients with chronic superficial Trichophyton rubrum infection have defective cellular immunity to dermatophyte antigens. This may be due to a selective anergy to dermatophyte antigens or reflect the activity of dermatophyte-derived lymphocyte inhibitory factors. To explore these possibilities, we assessed lymphocyte transformation to a variety of recall antigens, including a cytoplasmic and exoantigen preparation of Trichophyton rubrum in 15 patients with chronic dermatophyte infection and 15 age- and sex-matched positive controls. In a duplicate set of experiments, autologous serum was replaced by heat-inactivated fetal calf serum. In addition, the direct effect of Trichophyton rubrum extracts on lymphoproliferation was assessed in vitro. Comparable lymphocyte transformation to each recall antigen was observed in patients and controls. Moreover, we found no evidence for a circulating dermatophyte-derived lymphocyte inhibitory factor in sera from patients with chronic superficial infection. A direct inhibitory effect of Trichophyton rubrum on lymphocyte proliferation to recall antigens was observed, however, at protein concentrations of > 10 micrograms/ml (exoantigen preparation) and > 25 micrograms/ml (cytoplasmic preparation). This inhibitory effect was rapidly reversible, not associated with loss of cell viability and maximal when added within 24 h of antigen to cultured lymphocytes. Class II MHC antigen HLA-DR, a surface marker of T-cell activation, was observed on inhibited lymphocytes co-cultured with antigen, suggesting the primary target for the inhibitory effect in vitro is the lymphocyte rather than the antigen-presenting cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxocara canis: monoclonal antibodies to carbohydrate epitopes of secreted (TES) antigens localize to different secretion-related structures in infective larvae

The major secreted glycoproteins of Toxocara canis larvae appear to be derived from two specialized organs within the nematode organism. Using immunogold electron microscopy, we have analyzed the binding patterns of a panel of monoclonal antibodies (Tcn-1 to Tcn-8) reactive with Toxocara excretory-secretory (TES) antigens. We find, first, that the esophageal gland and lumen are strongly reactive with monoclonals Tcn-4, Tcn-5, and Tcn-8, and because the posterior portion of the gut is closed, we hypothesize that products of this gland are released through the oral aperture. Second, a distinct anti-TES antibody (Tcn-2) localizes solely to the midbody secretory column, which opens onto the cuticle at a secretory pore. Thus, the secretory apparatus is probably functional in this stage of parasite as an important source of TES products. Only one monoclonal, Tcn-7, can bind to both esophageal and secretory structures. In addition, another antibody, Tcn-3, binds both to the epicuticle and to a TES antigen, but our data do not directly determine whether antigens located in the cuticle are subsequently released. Thus there are at least two, and possibly three, independent sources of TES antigens within Toxocara larvae.

Postoperative low-dose heparin decreases thromboembolic complications in neurosurgical patients

Thromboembolic complications are a major cause of postoperative morbidity and mortality in the neurosurgical patient. Prophylaxis with lower extremity pneumatic compression boots (PCBs) reduces the incidence of lower extremity deep vein thrombosis (DVT) but has not been shown to affect the incidence of pulmonary embolism (PE). Prophylaxis with low-dose heparin has consistently reduced the incidence of both DVT and PE in studies on general surgical patients but has not been adopted for use in neurosurgery primarily for fear of causing catastrophic hemorrhage. We report on a series of 138 consecutive adult patients who underwent major neurosurgical procedures on a general neurosurgical service at our institution. Patients were treated with intraoperative PCBs and, starting on the morning of the first postoperative day, with a regimen of 5000 U of heparin administered subcutaneously twice daily. This treatment was continued until patients were fully ambulatory. PCBs were discontinued 24 hours after the first administration of heparin. None of the heparin-treated patients suffered postoperative hemorrhage. We compared this series with a control group of 473 adult patients who had previously undergone major neurosurgical procedures on the same neurosurgical service. These patients had been treated with intraoperative and postoperative PCBs alone. The control group had a 3.2% incidence of thromboembolic complications (15 of 473; eight DVT, seven PE). Prophylaxis with PCBs plus heparin significantly (P = 0.020) reduced the incidence of thromboembolic complications: no PCBs/heparin-treated patient exhibited clinical evidence of PE or DVT (0%, 0/138). We conclude that a combination of intraoperative PCBs and postoperative low-dose heparin is a safe and effective method by which to reduce thromboembolic complications in the neurosurgical patient.

A 34- to 38-kilodalton Cryptococcus neoformans glycoprotein produced as an exoantigen bearing a glycosylated species-specific epitope

Three monoclonal antibodies (MAbs), all of the immunoglobulin G1 subclass, were raised against Cryptococcus neoformans by using the technique of cyclophosphamide ablation of B-cell responses against shared epitopes of the cross-reactive fungus Trichosporon beigelii. MAb 3C2 was reactive against the encapsulated and nonencapsulated isolates of C. neoformans var. neoformans by enzyme-linked immunosorbent assay (ELISA) and Western blot (immunoblot), and in addition to a 34- to 38-kDa determinant, it recognized a series of lower-molecular-weight species. 3C2 also reacted strongly with culture supernatant preparations of C. neoformans var. neoformans by ELISA. 3C2 showed no recognition of either T. beigelii or C. neoformans var. gattii antigens. Enzymatic deglycosylation followed by reaction with 3C2 on Western blots revealed that sialic acid was an integral part of the determinant, together with N-acetylglucosaminyl-asparagine and alpha-mannose. Proteolytic digestion showed that the epitope was pepsin sensitive and that it also contained tryptophan and glycine and/or leucine as determinants of recognition by 3C2. The pI of the glycoprotein was 7.1. Affinity chromatography-purified antigen did not exhibit proteolytic activity on sodium dodecyl sulfate-polyacrylamide substrate gels. Indirect fluorescence antibody tests revealed that 3C2 labelling was confined to the cell membrane and cytoplasm of yeasts. The remaining MAbs, 7H4 and 5G5, recognized both capsulated and nonencapsulated strains of C. neoformans var. neoformans by both ELISA and Western Blot, identifying linear determinants with molecular masses of 36 and 30 kDa. They were unreactive against culture supernatant antigen (exoantigen) from either variant of C. neoformans.

Identification of a tomato gene for the ethylene-forming enzyme by expression in yeast

The ethylene-forming enzyme (EFE), which catalyzes the last step in the biosynthesis of the plant hormone ethylene, has never been purified and no molecular probes are available. Recently, a putative cDNA clone for tomato EFE (pTOM13) has been identified by inhibiting ethylene synthesis with an antisense gene expressed in transgenic plants. A direct test of its function has been made by expression of a pTOM13 gene in Saccharomyces cerevisiae. After cloning artefacts were discovered in the 5' region of the cDNA, a corrected cDNA (pRC13) was created by the fusion of the 5' end of a genomic clone to the 3' end of the cDNA and expressed in S. cerevisiae. Cultures of transformed yeast converted 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, whereas control cells did not. This EFE activity displays similar characteristics to EFE found in plant tissue: it converts the trans isomer of the ACC analogue 1-amino-2-ethylcyclopropane-1-carboxylic acid to 1-butene in preference to the cis isomer, and it is strongly inhibited by cobaltous ions and 1,10-phenanthroline. Furthermore, information gained from the activity of effectors on yeast EFE activity supports the hypothesis that EFE is one of a group of hydroxylase enzymes.

Plasma changes in beta-endorphin to acute hypobaric hypoxia and high intensity exercise

The purpose of this study was to examine the immediate post-exercise effects of acute exposure to a simulated altitude of 4,300 m on plasma concentrations of beta-endorphin (beta-EP) and associated changes of adrenocorticotropin (ACTH), and cortisol to high intensity cycle exercise (i.e., stages of 90 and 100% peak Vo2). Exercise intensities were assigned relative to peak O2 uptake both under sea level conditions and under acute hypobaric hypoxic conditions. Plasma beta-EP concentrations significantly increased from pre- to immediately post-exercise at both 90 and 100% peak Vo2 in both the sea level and acute hypobaric hypoxic trials. No associated exercise-induced changes were observed for ACTH or cortisol pre- to immediately post-exercise at either sea level or during hypoxic conditions. Exercise at acute hypobaric hypoxia elicited no significantly different responses in plasma beta-EP, ACTH, or cortisol than those elicited by the same relative exercise intensities under normobaric normoxic conditions. Additionally, no changes in the beta-EP/ACTH molar ratio for exercise or between conditions were observed. These data indicate that acute simulated high altitude exposure neither diminishes nor augments the physiological stimuli involved with high relative exercise intensity activation mechanisms of these hormones.

Alterations in human upper extremity motor function during acute exposure to simulated altitude

We tested the hypothesis that mild motor dysfunction was associated with Acute Mountain Sickness (AMS) by measuring arm movement characteristics in 14 subjects at sea level and at the end of a 30-h simulated altitude exposure (4,600 m). A computerized upper extremity movement analyzer (UEMA) was used to quantitate arm movements between a "start" position and randomly-generated targets on a large digitizing tablet by measuring selected speed parameters and error indices. The UEMA results were compared with the results of the Environmental Symptoms Questionnaire (ESQ) and with neurologic examinations. When compared with sea-level values, the mean values for all the speed-related parameters measured at the end of the 30-h exposure significantly declined by 20% to 32%. The error indices were not different. The declines in the speed-related parameters were significantly correlated with the severity of AMS symptoms as measured by the ESQ (R = 0.82). The neurologic abnormalities were limited to changes in mental status items. These results demonstrate that subclinical alterations in upper extremity speed are associated with mild, reversible AMS and provide evidence that hypoxia may produce supraspinal inhibition of motor pathways.

Production of species-specific murine monoclonal antibodies against Cryptococcus neoformans which recognize a noncapsular exoantigen

Three monoclonal antibodies (MAbs), designated 7C5, 7C9, and 5G8, against a cytoplasmic antigen of Cryptococcus neoformans were produced. MAbs 7C5 and 7C9 recognize culture filtrate antigen (exoantigen) of both encapsulated and nonencapsulated isolates of this pathogen, which suggests that they do not recognize capsular polysaccharide material. This is supported by immunofluorescence data which show reactivity of all 3 MAbs to cytoplasm and cell membranes only. MAb 7C9 also recognized C. neoformans var. gattii antigens but no other fungal pathogens tested in an enzyme-linked immunosorbent assay, while 7C5 and 5G8 recognized antigens of the cross-reactive pathogen Trichosporon beigelii but did not recognize either C. neoformans var. gattii isolates or any other fungal antigens. By Western blot (immunoblot), 7C9 detected antigen at 110 to 120, 65 to 70, 45 to 50, and 36 to 38 kDa; in addition to the latter band, the other two MAbs recognized a band at approximately 30 kDa. All three MAbs were of the immunoglobulin G1 subclass. The two MAbs which are capable of reacting with noncapsular culture supernatant antigen have possible uses in serodiagnosis, particularly in AIDS patients infected with C. neoformans, since in this group the present latex agglutination test has some limitations.

Pseudopsammomatous meningioma with elevated serum carcinoembryonic antigen: a true secretory meningioma. Case report

A sphenoid-wing meningioma in a 60-year-old woman was accompanied by elevated serum carcinoembryonic antigen (CEA) levels, which returned to normal after removal of the tumor. Light microscopic examination revealed a secretory meningioma containing numerous pseudopsammoma bodies and a prominent vascular pattern. Immunohistochemical analysis showed the tumor cells and pseudopsammoma bodies to be CEA-positive. This case illustrates the possibility that secretory meningioma may be associated with clinically detectable secretion of CEA. The report also documents the rare occurrence of elevated serum CEA in a primary benign intracranial tumor.

Murine monoclonal antibodies recognizing a non-capsular antigen that distinguishes between Cryptococcus neoformans var. neoformans and C. neoformans var. gattii

A panel of 4 monoclonal antibodies (mabs) of the IgG1 subclass have been made against a cytoplasmic antigen of Cryptococcus neoformans. Mab 4E2 recognized isolates of C. neoformans var. gatti by enzyme-linked immunosorbent assay (ELISA), whilst the other antibodies did not recognize these antigens. By Western blot 4E2 recognized determinants at 110-125, 65-70, 45-50 and 36-38 kDa. Mabs 9E6, 7C7 and 5D9 recognized bands at 36-38 and approximately 30 kDa. All 4 mabs (4E2, 9E6, 7C7 and 5D9) recognized both non-encapsulated and encapsulated isolates of C. neoformans var. neoformans by ELISA, and in addition showed reactivity to only the cytoplasm and cell membrane of yeasts by immunofluorescence. Mab 7C7 recognized antigens of the closely related fungus Trichosporon beigelii by ELISA but did not recognize any other fungal antigens. The other 3 mabs showed no recognition of T. beigelii or any other fungal pathogens tested.

Preparation of murine monoclonal antibodies against the yeast phase of the dimorphic fungus Sporothrix schenckii

Three murine monoclonal antibodies (Mabs) were raised against a cytoplasmic antigen of the yeast phase of the pathogenic fungus Sporothrix schenckii using a modification of standard hybridoma technology incorporating the immunosuppressive drug cyclophosphamide. When tested for species-specificity within the pathogenic dimorphic fungi one of these Mabs (S5) showed little cross-reactivity by enzyme-linked immunosorbent assay and Western blot, though there was some recognition of Paracoccidioides brasiliensis antigen. This Mab recognized a 70-75 kDa molecule on reduced Western blots of S. schenckii antigen. The other two Mabs (S12 and S15) showed cross-reactivity with all dimorphic fungal antigens tested, though they appeared to recognize a molecule of similar molecular weight. This is the first report of any attempt to raise species-specific Mabs against this important causative agent of dermatological disease.

Preparation of monoclonal antibodies that differentiate between Histoplasma capsulatum variant capsulatum and H. capsulatum variant duboisii

The immunosuppressive drug cyclophosphamide was used to facilitate the production of monoclonal antibodies (Mabs) which differentiated between the yeast phase of the two variants of the dimorphic fungus Histoplasma capsulatum by both enzyme-linked immunosorbent assay and Western blot. Two Mabs are described, identifying epitopes on a 70-75 kDa molecule, which are specific to H. capsulatum var. capsulatum and which do not identify epitopes of H. capsulatum var. duboisii. These Mabs have potential use in the epidemiology and serodiagnosis of histoplasmosis in areas where both classical and African forms of the disease occur.

A murine monoclonal antibody exhibiting high species specificity for Histoplasma capsulatum var. capsulatum

A monoclonal antibody (mAb) exhibiting a high degree of species specificity for the yeast phase of the dimorphic fungus Histoplasma capsulatum was produced by a modification of the standard mAb production protocol. The technique for generating mAbs involved the use of the immunosuppressive drug cyclophosphamide to diminish the response in mice to immunodominant cross-reactive epitopes. This mAb exhibited clear specificity and did not react by ELISA with the closely related genera Blastomyces, Paracoccidioides and Sporothrix. In Western blots it recognized a linear determinant on a 70-75 kDa molecule in H. capsulatum antigen, with an extremely faint reactivity to antigens of identical molecular mass derived from Sporothrix and Paracoccidioides, and no reactivity against Blastomyces antigen.

Localization and immunogenicity of tubulin in the filarial nematodes Brugia malayi and B. pahangi

Tubulin was identified in the filarial nematodes Brugia malayi and B. pahangi by several approaches. Initially, a monoclonal antibody (6D8) was selected for its unusual binding to B. malayi microfilariae in indirect immunofluorescence assays: 6D8 showed granular, heterogeneously dispersed fluorescence on fixed parasites but did not bind to unfixed microfilariae. The microfilarial sheath did not bind 6D8, although it did bind fluoresceinated wheatgerm agglutinin. By Western blotting against microfilarial sonicate, 6D8 reacted with a 50,000-55,000 mol. wt protein, and also bound to purified chicken brain beta-tubulin. Additionally, this monoclonal antibody reacted with a recombinant fusion protein expressed by a clone (Bpa-7) originally isolated from an adult B. pahangi cDNA expression library by its reaction with chronic human filariasis serum. This clone encodes a small 40 amino acid C-terminal segment corresponding to residues 409-449 of beta-tubulin, and shows complete amino acid sequence homology with vertebrate beta-tubulin from 409 to 430 but 55% divergence (six amino acid substitutions, four insertions and one deletion) from human and chicken beta-tubulin over positions 431-449 at the C terminus. Antibody to both parasite and vertebrate (chicken) tubulin was found in filarial infection sera, with higher levels of autoreactive antibody apparent in amicrofilaraemic individuals. Immunogold electron microscopy was then used to localize beta-tubulin in B. malayi microfilariae and adult worms. Tubulin was shown not to be exposed on the microfilarial sheath or in the cuticle of either stage, but was found to be abundant in the somatic tissues. In microfilariae, 6D8 bound myofibril structures under the hypodermal layer, and also bound within cell nuclei. In the adult stage, tubulin was associated with muscle blocks, as well as the intestinal brush border and the embryonic uterine microfilariae.

Immunogold electron microscopical detection of tubulin and actin within mycelial phase Histoplasma capsulatum capsulatum and H. capsulatum duboisii

Immunogold electron microscopy using LR Gold as a resin was undertaken to determine the distribution of actin and tubulin within the hyphae of Histoplasma capsulatum capsulatum and H. capsulatum duboisii. Both of these proteins were found throughout the cytoplasm when probed with the appropriate monoclonal antibodies.

Increased exercise SaO2 independent of ventilatory acclimatization at 4,300 m

Arterial O2 saturation (Sao2) decreases in hypoxia in the transition from rest to moderate exercise, but it is unknown whether other several weeks at high altitude SaO2 in submaximal exercise follows the same time course and pattern as that of ventilatory acclimatization in resting subjects. Ventilatory acclimatization is essentially complete after approximately 1 wk at 4,300 m, such that improvement in submaximal exercise SaO2 would then require other mechanisms. On days 2, 8, and 22 on Pikes Peak (4,300 m), 6 male subjects performed prolonged steady-state cycle exercise at 79% maximal O2 uptake (VO2 max). Resting SaO2 rose from day 1 (78.4 +/- 1.6%) to day 8 (87.5 +/- 1.4%) and then did not increase further by day 20 (86.4 +/- 0.6%). During exercise, SaO2 values (mean of 5-, 15-, and 30-min measurements) were 72.7% (day 2), 78.6% (day 8), and 82.3% (day 22), meaning that all of the increase in resting SaO2 occurred from day 1 to day 8, but exercise SaO2 increased from day 2 to day 8 (5.9%) and then increased further from day 8 to day 22 (3.7%). On day 22, the exercise SaO2 was higher than on day 8 despite an unchanged ventilation and O2 consumption. The increased exercise SaO2 was accompanied by decreased CO2 production. The mechanisms responsible for the increased exercise SaO2 require further investigation.

Oxygen transport to exercising leg in chronic hypoxia

Residence at high altitude could be accompanied by adaptations that alter the mechanisms of O2 delivery to exercising muscle. Seven sea level resident males, aged 22 +/- 1 yr, performed moderate to near-maximal steady-state cycle exercise at sea level in normoxia [inspired PO2 (PIO2) 150 Torr] and acute hypobaric hypoxia (barometric pressure, 445 Torr; PIO2, 83 Torr), and after 18 days' residence on Pikes Peak (4,300 m) while breathing ambient air (PIO2, 86 Torr) and air similar to that at sea level (35% O2, PIO2, 144 Torr). In both hypoxia and normoxia, after acclimatization the femoral arterial-iliac venous O2 content difference, hemoglobin concentration, and arterial O2 content, were higher than before acclimatization, but the venous PO2 (PVO2) was unchanged. Thermodilution leg blood flow was lower but calculated arterial O2 delivery and leg VO2 similar in hypoxia after vs. before acclimatization. Mean arterial pressure (MAP) and total peripheral resistance in hypoxia were greater after, than before, acclimatization. We concluded that acclimatization did not increase O2 delivery but rather maintained delivery via increased arterial oxygenation and decreased leg blood flow. The maintenance of PVO2 and the higher MAP after acclimatization suggested matching of O2 delivery to tissue O2 demands, with vasoconstriction possibly contributing to the decreased flow.

Expression of circumsporozoite proteins revealed in situ in the mosquito stages of Plasmodium berghei by the Lowicryl-immunogold technique

A monoclonal antibody against the circumsporozoite proteins of the Plasmodium berghei sporozoite was used to trace the synthesis and expression of these proteins, via the Lowicryl immunogold technique, within the developing oocyst. The proteins were detected on the endoplasmic reticulum of the oocyst and were present in the sporozoite membranes at the point of their formation.

The fate of the circumsporozoite antigens during the exoerythrocytic stage of Plasmodium berghei

There has been considerable interest in the circumsporozoite proteins due to their potential use in anti-malarial vaccines. Previous authors have shown that these proteins persist from the invading sporozoite throughout the growing exoerythrocytic or liver stage. We show that the different distributions of these proteins seen during the development of the exoerythrocytic parasite of Plasmodium berghei closely follow morphological changes, which can be recognized under the light microscope. At the end of the exoerythrocytic cycle, the majority of the remaining circumsporozoite proteins were associated with the spongy stroma in which the emerging exoerythrocytic merozoites lay. Cell-mediated immunity originally directed against sporozoites might recognize the stroma as a second target resulting in the indirect destruction of the exoerythrocytic merozoites.

Immunoelectron microscopic localization of circumsporozoite antigen in the differentiating exoerythrocytic trophozoite of Plasmodium berghei

The distribution of the circumsporozoite (CS) antigens in the 24 hour exoerythrocytic trophozoite of P. berghei was studied using Lowicryl immunogold electron microscopy. These antigens were present on the plasmalemma of the parasite, in disrupted areas of the host cell cytoplasm adjacent to the trophozoite and around inclusions of the host cell cytoplasm. There was evidence of a redistribution of the CS antigens away from the pellicular region of the sporozoite.

High altitude cerebral edema

Acute mountain sickness (AMS) is usually a benign and self-limited illness that befalls previously healthy individuals who ascend rapidly to high altitude without sufficient acclimatization. In its more severe forms, AMS can progress to a life-threatening condition in which pulmonary or cerebral edema can occur singly or in concert. High altitude cerebral edema (HACE) is a little-known clinical entity that manifests itself by a perplexing array of both generalized and localized neurological symptoms and signs. Furthermore, the development of HACE in climbers offers a unique experimental situation in which to examine the effects of hypoxia on the central nervous system. The epidemiology and clinical picture of HACE are reviewed. In addition, the pathology and predominant pathophysiological mechanisms postulated to explain HACE are examined, and the present recommendations for the prevention and treatment of this dangerous and unusual form of brain swelling are discussed.

Neuropeptide investigations with an ovine surgical model

An ovine surgical model for peptide investigations is presented. Techniques for exteriorization of the carotid artery, catheterization of the sagittal sinus, hypophysectomy via a transnasopharyngeal approach, and ventricular and cisternal cannulation in the sheep are employed within the model. Several experimental applications in neurosurgical research are presented.

Contrasting actions of naloxone in experimental spinal cord trauma and cerebral ischemia: a review

Endorphins have been implicated in the pathophysiology of both spinal cord injury and cerebral ischemia. This review examines the nature of the experimental evidence to support this hypothesis. Present studies suggest that naloxone administration improves neurological function and outcome in the setting of the spinal cord trauma by centrally inhibiting an opiate receptor-mediated diminution of spinal cord flow. In the setting of spinal shock, naloxone administration is associated with improvement in vital sign and cardiovascular parameters as measured by mean arterial pressure, cardiac output, body temperature, and ventilation. Experiments using a variety of animal stroke models similarly support the notion that naloxone improves neurological function in the setting of cerebral ischemia by a stereospecific opiate receptor-mediated effect, but this improvement does not seem to be accompanied by augmentation of blood flow to affected areas of the brain or by any improvement in vital signs or cardiovascular parameters as seen in spinal cord trauma. A variety of mechanisms are discussed to explain these observations. The therapeutic implications of administering opiate agonists and antagonists in the setting of neurological deficits are outlined for the neurosurgeon.

Polytetrafluoroethylene grafts in the peripheral venous circulation of rabbits

We demonstrated by venography that the patency of 3 mm PTFE grafts in the jugular veins of rabbits could be maintained by pretreating the animals with either an anticoagulant (warfarin sodium) or an antiplatelet agent (aspirin, dipyridamole, or both). Examination of the lining of the grafts up to 4 months after grafting by scanning electron microscopy or light microscopy showed that endothelial cells extended across the anastomosis for a short distance and that a neointima lined the remainder of the graft. This lining could hypertrophy to the point of almost occluding the graft unless the drugs were continued.

Desensitization of the cholinergic receptor at the sinoatrial cell of the kitten

The hyperpolarizing effects of long periods of vagal stimulation were studied in kitten sinoatrial node-vagus nerve preparations. Verapamil (2.2 x 10(-6) M) was used to arrest spontaneous pacemaker activity, thus permitting uninterrupted observation of the time course of cholinergically mediated hyperpolarizations. With progressively longer vagal trains the hyperpolarization was not maintained but decreased, rapidly at first, and then more gradually despite continuous vagal stimulation. Similar decay of the cholinergic effect was also observed during continuous iontophoretic application of acetylcholine (ACh) or carbamylcholine (CCh). The results show that, for the most part, the decay of the hyperpolarizing response cannot be due to "fatigue" of nerve terminals, to a gradual reduction in the driving force for K+, or to hydrolysis of ACh by cholinesterase. These experiments demonstrate the development of desensitization of the cholinergic receptor at the sinoatrial cell membrane. The data fit the "cyclic reaction" model proposed by Katz and Thelsleff (J. Physiol. London 138:63-80, 1957) for the neuromuscular junction.

Effects of current flow on pacemaker activity of the isolated kitten sinoatrial node

The dynamic behavior of the cardiac pacemaker in response to single or to periodically repeated perturbations was studied using kitten sinoatrial (SA) nodal strips mounted in a sucrose gap. Sustained stepwise applications of current across the gap produce lasting variations in pacemaker cycle length that depend on current magnitude and polarity, but not on the phase of the pacemaker period at the time of the input. Brief current pulses, whether hyperpolarizing or depolarizing, may abbreviate or prolong the immediately affected cycle depending on their timing. These changes result in phase shifts of the subsequent discharges, but they do not alter the pacemaker period permanently. The phasic effects of brief current pulses can be described by a phase response curve (PRC), which is a plot of the phase shift as a function of the position of the stimulus in the pacemaker cycle. PRCs were constructed for inputs of different polarity and several strengths and durations. The behavior of the sinus nodal pacemaker when interacting with period perturbing inputs, such as vagal stimulation or electrotonic depolarization, can be predicted on the basis of the phase response curve.

End Results of Surgical Treatment of Diseases of the Stomach and Duodenum

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