Robust anti-arrhythmic efficacy of verapamil and flunarizine against dofetilide-induced TdP arrhythmias is based upon a shared and a different mode of action

BACKGROUND AND PURPOSE

The high predisposition to Torsade de Pointes (TdP) in dogs with chronic AV-block (CAVB) is well documented. The anti-arrhythmic efficacy and mode of action of Ca(2+) channel antagonists, flunarizine and verapamil against TdP were investigated.

EXPERIMENTAL APPROACH

Mongrel dogs with CAVB were selected based on the inducibility of TdP with dofetilide. The effects of flunarizine and verapamil were assessed after TdP and in different experiments to prevent dofetilide-induced TdP. Electrocardiogram and ventricular monophasic action potentials were recorded. Electrophysiological parameters and short-term variability of repolarization (STV) were determined. In vitro, flunarizine and verapamil were added to determine their effect on (i) dofetilide-induced early after depolarizations (EADs) in canine ventricular myocytes (VM); (ii) diastolic Ca(2+) sparks in RyR2(R4496+/+) mouse myocytes; and (iii) peak and late I(Na) in SCN5A-HEK 293 cells.

KEY RESULTS

Dofetilide increased STV prior to TdP and in VM prior to EADs. Both flunarizine and verapamil completely suppressed TdP and reversed STV to baseline values. Complete prevention of TdP was achieved with both drugs, accompanied by the prevention of an increase in STV. Suppression of EADs was confirmed after flunarizine. Only flunarizine blocked late I(Na). Ca(2+) sparks were reduced with verapamil.

CONCLUSIONS AND IMPLICATIONS

Robust anti-arrhythmic efficacy was seen with both Ca(2+) channel antagonists. Their divergent electrophysiological actions may be related to different additional effects of the two drugs.

Substance use among university students at the St Augustine campus of the University of the West Indies

OBJECTIVE

Substance use and abuse is a well known public health risk that peaks in persons between 18 and 25 years of age and is prevalent among university students. While this has been repeatedly documented in developed nations, there have been limited studies in the English-speaking Caribbean. This study therefore sought to assess the prevalence of alcohol, tobacco and marijuana use among university students in the English-speaking Caribbean and any associated risk factors.

METHODS

The study was designed as a descriptive, cross-sectional study to assess substance use in full-time, undergraduate students of The University of the West Indies (UWI), Trinidad and Tobago, over a six-month period. Questionnaires were distributed and students asked to self-report on their use of alcohol, tobacco and marijuana during the preceding six months.

RESULTS

The six-month prevalence rate for alcohol was 70% and 28% of students were identified as regular users. Binge drinking was estimated at 31%. Muslims were least likely to have used alcohol when compared to other religious groupings. The prevalence rate for tobacco and marijuana was 17% and 13%, respectively Ten per cent used all three substances. The use of all three substances was associated with multiple problems.

CONCLUSION

We conclude that substance use is common among many students of the UWI but generally lower than reports from other regions of the world. Despite this, substance use is associated with a number of problems and immediate educational interventions may be necessary to assist students in making informed and responsible choices.

Antibody effector mechanisms in myasthenia gravis-pathogenesis at the neuromuscular junction

Myasthenia gravis (MG) is an autoimmune disorder caused by autoantibodies that are either directed to the muscle nicotinic acetylcholine receptor (AChR) or to the muscle-specific tyrosine kinase (MuSK). These autoantibodies define two distinct subforms of the disease-AChR-MG and MuSK-MG. Both AChR and MuSK are expressed on the postsynaptic membrane of the neuromuscular junction (NMJ), which is a highly specialized region of the muscle dedicated to receive and process signals from the motor nerve. Autoantibody binding to proteins of the postsynaptic membrane leads to impaired neuromuscular transmission and muscle weakness. Pro-inflammatory antibodies of the human IgG1 and IgG3 subclass modulate the AChR, cause complement activation, and attract lymphocytes; together acting to decrease levels of the AChR and AChR-associated proteins and to reduce postsynaptic folding. In patients with anti-MuSK antibodies, there is no evidence of loss of junctional folds and no apparent loss of AChR density. Anti-MuSK antibodies are predominantly of the IgG4 isotype, which functionally differs from other IgG subclasses in its anti-inflammatory activity. Moreover, IgG4 undergoes a posttranslational modification termed Fab arm exchange that prevents cross-linking of antigens. These findings suggest that MuSK-MG may be different in etiological and pathological mechanisms from AChR-MG. The effector functions of IgG subclasses on synapse structure and function are discussed in this review.

The impact of steroids given with macrolide therapy on experimental Mycoplasma pneumoniae respiratory infection

BACKGROUND

Systemic steroids have been advocated in addition to antimicrobial therapy for severe Mycoplasma pneumoniae pneumonia. We evaluated the efficacy of clarithromycin, dexamethasone, and combination therapy for M. pneumoniae respiratory infection.

METHODS

Mice infected with M. pneumoniae were treated with clarithromycin, dexamethasone, combined clarithromycin/dexamethasone, or placebo daily; mice were evaluated at baseline and after 1, 3, and 6 days of therapy. Outcome variables included M. pneumoniae culture, lung histopathologic score (HPS), and bronchoalveolar lavage cytokine, chemokine, and growth factor concentrations.

RESULTS

Clarithromycin monotherapy resulted in the greatest reductions in M. pneumoniae concentrations. After 3 days of treatment, combination therapy significantly reduced lung HPS compared with placebo, clarithromycin, and dexamethasone alone, whereas, after 6 days of therapy, clarithromycin alone and combination therapy significantly reduced lung HPS compared with placebo. Concentrations of interleukin (IL)-12 p40, RANTES, macrophage chemotactic protein-1, and cytokine-induced neutrophil chemoattractant were significantly lower in mice treated with clarithromycin alone and/or combination therapy compared with dexamethasone alone and/or placebo; combination therapy resulted in a significantly greater reduction than clarithromycin alone for IL-12 p40 and RANTES.

CONCLUSIONS

Although monotherapy with clarithromycin had the greatest effect on reducing concentrations of M. pneumoniae, combination therapy had the greatest effect on decreasing levels of cytokines and chemokines as well as pulmonary histologic inflammation.

HIV type 1 genetic diversity surveillance among newly diagnosed individuals from 2003 to 2005 in Buenos Aires, Argentina

To perform a diversity surveillance study we characterized viral subtypes among newly diagnosed individuals in Buenos Aires city. Plasma samples were collected from 322 drug-naive newly diagnosed HIV-1 individuals attending two voluntary counseling and testing centers. Sequences of pol and vpu genes were obtained from 283 samples and viral subtype was characterized by Neighbor-joining trees and Bootscanning analysis. BF recombinants were found in 56.9% followed by subtype B strains (39.2%). CRF12_BF structure was found in 27% of BF while another 27% had that structure only in one of both genes analyzed. Unusual non-B-non-BF strains were found in 3.9% (11/283). They were further analyzed by database searching and maximum likelihood trees in order to track their origin. Two subtype C sequences were found to be related to South American isolates while another two subtype C sequences and the subtype C segment of a BC recombinant were found to be related to isolates from Senegal. We also identified the CRF16_A2D previously found in Argentina and the CRF06_cpx commonly prevalent in Africa. The B segment of a BD recombinant was also found to be related to the Argentinean Bs suggesting a recombination between an African and a local strain. We also found a BK and two BA recombinants. In conclusion, CRF16_A2D and a new line of subtype C (of Senegalese origin) seem to be successfully established and are now spreading in Buenos Aires. BF recombinants keep recombining with local strains losing the CRF12_BF structure. Altogether they are changing the diversity of HIV in Argentina.

Treatment of carotid cavernous fistulas using covered stents: midterm results in seven patients

BACKGROUND AND PURPOSE

Carotid cavernous fistulas (CCF) can be effectively treated by using different therapeutic alternatives such as detachable balloons and detachable coils, alone or in combination with N-butyl-2-cyanoacrylate (n-BCA) or Onyx. Stents have also been used in an attempt to improve preservation of the parent artery while still occluding the fistula. We present our experience using balloon-expandable covered stents to treat CCF, focusing on arterial wall reconstruction. To our knowledge, this is the first series with midterm follow-up between 3 months and 3.5 years.

MATERIALS AND METHODS

From the 46 CCF treated at our institution between November 1998 and September 2006, a total of 7 posttraumatic direct CCF were treated using polytetrafluoroethylene (PTFE)-covered stents between April 2003 and September 2006. Five were treated with covered stents alone. One patient with transection of the internal carotid artery (ICA) first underwent bare stent placement to provide support for the covered stent. One patient had to be treated with coils and n-BCA.

RESULTS

Control angiograms obtained in the 7 patients demonstrated occlusion of the fistula and preservation of the ICA in all cases. There was no mortality and no immediate postprocedural morbidity. There was 1 case of morbidity identified at 1-month follow-up with asymptomatic occlusion of the ICA; the other 6 patients had angiographic follow-up between 3 and 42 months (mean, 18.4 months), with persistent occlusion of the fistulas, patent stent grafts, and no significant intimal hyperplasia.

CONCLUSIONS

PTFE-covered stents are evolving as a promising intracranial therapeutic alternative to treat CCF and preserve the parent artery by reconstructing the arterial wall. They should be considered in patients in whom fistulas cannot be successfully occluded with detachable balloons or detachable coils. More investigation is required to further develop their specifications and indications.

Drug-resistance surveillance among newly HIV-1 diagnosed individuals in Buenos Aires, Argentina

OBJECTIVE

Our objective was to estimate primary resistance in an urban setting in a developing country with a long history of antiretroviral delivery and high coverage levels.

DESIGN

We carried out a resistance surveillance study according to WHO HIV-Resistance Guidelines.

METHODS

Blood samples were collected from 323 drug-naive HIV-1 infected individuals diagnosed at two HIV voluntary counselling and testing centers in Buenos Aires. Viral-load, CD4 cell counts and detuned assays were performed on all samples. The pol gene was sequenced and the resistance profile determined. Phylogenetic analysis was performed by neighbor-joining trees and bootscanning analysis.

RESULTS

We found that 12 (4.2%) of the 284 samples sequenced harbored primary resistance mutations, of which K103N, M41L and V108I were most prevalent. Phylogenetic analysis revealed evidence for the transmission of the K103N mutation among the drug-naive population. The proportion of recent infections identified by the detuned assay was 10.1%.

CONCLUSIONS

Levels of primary resistance in Buenos Aires are still low, despite a long history of ARV delivery and high coverage levels.

Respiratory tract infection with Mycoplasma pneumoniae in interleukin-12 knockout mice results in improved bacterial clearance and reduced pulmonary inflammation

Mycoplasma pneumoniae is a leading cause of pneumonia and is associated with asthma. Evidence links M. pneumoniae respiratory disease severity with interleukin-12 (IL-12) concentration in respiratory secretions. We evaluated the microbiologic, inflammatory, and pulmonary function indices of M. pneumoniae pneumonia in IL-12 (p35) knockout (KO) mice and wild-type (WT) mice to determine the role of IL-12 in M. pneumoniae respiratory disease. Eight-week-old wild-type BALB/c mice and 8-week-old IL-12 (p35) KO BALB/c mice were inoculated once intranasally with 10(7) CFU of M. pneumoniae. Mice were evaluated at days 2, 4, and 7 after inoculation. Outcome variables included quantitative bronchoalveolar lavage (BAL) M. pneumoniae culture, lung histopathologic scores (HPS), BAL cytokine concentrations determined by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor) and plethysmography, before and after methacholine, to assess airway obstruction (AO) and airway hyperreactivity (AHR). IL-12 (p35) KO mice infected with M. pneumoniae were found to have significantly lower BAL M. pneumoniae concentrations compared with M. pneumoniae-infected WT mice. Lung HPS and the parenchymal pneumonia subscores (neutrophilic alveolar infiltrate), as well as AO, were significantly lower in infected KO mice. No difference was found for AHR. Infected KO mice had significantly lower BAL concentrations of IFN-gamma than WT mice; a trend toward lower BAL concentrations was observed for IL-10 (P = 0.065) and TNF-alpha (P = 0.078). No differences were found for IL-1beta, IL-2, IL-4, IL-5, or IL-6. The lack of IL-12 in experimental M. pneumoniae pneumonia was associated with less severe pulmonary disease and more rapid microbiologic and histologic resolution.

New perspectives on the key role of calcium in the progression of heart disease

The heart continuously adapts to adjust its output to a continuum of pathophysiological situations ensuring adequate blood distribution. These situations range from high performance in well-trained athletes to failure in a variety of cardiac syndromes. Changes in the concentration of intracellular Ca2+ ([Ca2+]i) are crucial. They have immediate and late effects that can be oversimplified as follows. Immediate effects result from abrupt and large variations in [Ca2+]i triggering contraction after binding to the contractile proteins. These variations are involved in the process known to as excitation-contraction (EC) coupling. In contrast, the late effects involve a process that is, by analogy, referred to as excitation-transcription (ET) coupling. This process involves activation of gene expression by Ca2+. In this scheme, specific and localised elevations of Ca2+ can be converted into changes in gene expression with long-term effects on the adaptation of the heart to a sustained stimulus. There is emerging evidence of an extraordinary diversity of responses, depending on the location, intensity, and duration of Ca2+ signals that can be activated during pathology. Whereas alterations of cellular and molecular mechanisms underlying chronic pathology are relatively well defined, the initial changes and their hierarchy are unknown. However, the actual picture suggests promising perspectives for new therapeutic interventions on old targets or new strategies. Some of these aspects are reviewed here.

A pilot C282Y hemochromatosis screening in Italian newborns by TaqMan technology

Hereditary hemochromatosis (HH) is a disorder of iron metabolism that leads to iron overload in middle age and can be caused by homozygosity for the C282Y mutation in the HFE gene. Preliminary studies have estimated the frequency of this mutation at 0.5-1% in Italy, but this has not been verified on a large sample. We analyzed 1,331 Italian newborns for the C282Y mutation in the HFE gene using dried blood spots (DBS) from the Neonatal Screening Center in Turin, Italy. The mutation was assessed using a semi-automatable 5'-nuclease assay (TaqMan technology). We detected 55 heterozygotes and no homozygotes in our sampling, resulting in an overall frequency of 2.1% +/- 0.6 for the C282Y allele. Differences in allele frequency were observed, and ranged from 2.7% +/- 1.3 in samples from Northern Italy, to 1.7% +/- 0.9 in samples from Central-Southern Italy. The low frequency of the at-risk genotype for iron overload suggests that genetic screening for HFE in Italy would not be cost effective. The present study, in addition to defining C282Y frequency, documents detection of the major HFE mutation on routine DBS samples from neonatal screening programs using a semi-automatable, rapid, reliable, and relatively inexpensive approach.

Suppression of voltage-gated L-type Ca2+ currents by polyunsaturated fatty acids in adult and neonatal rat ventricular myocytes

Our recent data show that in cardiac myocytes polyunsaturated fatty acids (PUFAs) are antiarrhythmic. They reduce I(Na), shorten the action potential, shift the threshold for excitation to more positive potentials, and prolong the relative refractory period. In this study we use patch-clamp techniques in whole-cell mode and confocal Ca2+ imaging to examine the effects of PUFAs on the voltage-gated L-type Ca2+ current (I(Ca,L)), elementary sarcoplasmic reticulum Ca2+-release events (Ca2+-sparks), and [Ca2+]i transients in isolated rat ventricular myocytes. Extracellular application of eicosapentaenoic acid (EPA; C20:5 n - 3) produced a prompt and reversible concentration-dependent suppression of I(Ca,L). The concentration of EPA to produce 50% inhibition of I(Ca) was 0.8 microM in neonatal rat heart cells and 2.1 microM in adult ventricular myocytes. While the EPA induced suppression of I(Ca,L), it did not significantly alter the shape of the current-voltage relation but did produce a small, but significant, negative shift of the steady-state inactivation curve. The inhibition of I(Ca,L) was voltage- and time-dependent, but not use- or frequency-dependent. Other PUFAs, such as docosahexaenoic acid, arachidonic acid, linolenic acid, linoleic acid, conjugated linoleic acid, and eicosatetraynoic acid had similar effects on I(Ca,L) as EPA. All-trans-retinoic acid, which had been shown to suppress induced arrhythmogenic activity in rat heart cells, also produced a significant inhibition of I(Ca,L). The saturated stearic acid and the monounsaturated oleic acid had no effect on I(Ca,L). Because both I(Ca,L) and sarcoplasmic reticulum Ca2+-release underlie many cardiac arrhythmias, we examined the effects of EPA on I(Ca,L) and Ca2+-sparks. While EPA suppressed both, it did not change the temporal or spatial character of the Ca2+-sparks, nor did it alter the ability of I(Ca,L) to trigger Ca2+-sparks. We conclude that PUFAs may act as antiarrhythmic agents in vivo in normal and Ca2+-overloaded cells principally because they reduce Ca2+ entry by blocking I(Ca,L). Furthermore, PUFAs act directly to decrease I(Na) and I(Ca,L), but indirectly to reduce the [Ca2+]i transients and [Ca2+]i-activated membrane current. Although a negative inotropic action is associated with application of PUFAs, it is clear that by reducing I(Ca,L), I(Na) and Ca2+-sparks, PUFAs can reduce spontaneous extrasystoles in the heart. The mechanisms by which PUFAs act are discussed.

Actin plays a role in both changes in cell shape and gene-expression associated with Schwann cell myelination

Schwann cell (SC) differentiation into a myelinating cell requires concurrent interactions with basal lamina and an axon destined for myelination. As SCs differentiate, they undergo progressive morphological changes and initiate myelin-specific gene expression. We find that disrupting actin polymerization with cytochalasin D (CD) inhibits myelination of SC/neuron co-cultures. Basal lamina is present, neurons are healthy, and the inhibition is reversible. Electron microscopic analysis reveals that actin plays a role at two stages of SC differentiation. At 0.75-1.0 microg/ml CD, SCs do not differentiate and appear as "rounded" cells in contact with axons. This morphology is consistent with disruption of actin filaments and cell shape changes. However, at 0.25 microg/ml CD, SCs partially differentiate; they elongate and segregate axons but generally fail to form one-to-one relationships and spiral around the axon. In situ hybridizations reveal that SCs in CD-treated cultures do not express mRNAs encoding the myelin-specific proteins 2',3'-cyclic nucleotide phosphodiesterase (CNP), myelin-associated glycoprotein (MAG), and P0. Our results suggest that at the lower CD dose, SCs commence differentiation as evidenced by changes in cell shape but are unable to elaborate myelin lamellae because of a lack of myelin-specific mRNAs. We propose that F-actin influences myelin-specific gene expression in SCs.

Inhibition of HIV-1-induced syncytia formation and infectivity by lipophosphoglycan from Leishmania

In HIV-1 infection, the appearance of syncytia-inducing (SI) isolates is associated with a more rapid decline of CD4+ cells and progression to AIDS. Agents that inhibit either virus infection or syncytia formation have the potential to be therapeutically useful. Lipophosphoglycan (LPG), the major glycoconjugate of Leishmania, was recently shown to be a potent nonspecific inhibitor of viral membrane fusion. In this study, LPG demonstrated a dose-dependent inhibition of HIV-1-induced syncytia formation in CD4+ MT-2 cells infected with distinct SI isolates. Fragments of LPG were used to show that inhibition of syncytia formation was dependent on the length of the LPG fragment. Treatment of CD4+ cells or HIV-1 isolates with LPG inhibited infection in vitro. Furthermore, LPG inhibited the replication of SI viral isolates in CD4+ T cells in vitro. LPG had no toxic effects on peripheral blood mononuclear cells at the highest concentrations used in these assays. Further, LPG rapidly associated with the surface membrane of a human T cell line and subsequently disassociated over a 24-h period. The development of compounds capable of inhibiting HIV-induced syncytia formation should provide novel therapeutic approaches to control the spread of virus and disease progression.

Cyclization Reactions of Tethered Radicals Derived From 4-O-Substituted α-D-erythro-Octa-2,6-dienopyranosides: Stereoselective Access to Carbocycles and Branched-Chain Sugars

The chemo- and stereo- selectivities in the cyclization of tethered radicals, derived from α-D-erythro-octa-2,6-dienopyranosides, in which there is competition between 5-exo and 6-exo ring closures, have been examined. Use of silicon tethers resulted in a preferred 6-exo-trig addition. However, tethered mixed iodo acetals have shown an unprecedented relation between the stereogenic centre in the acetal and the preferred addition pathway. In addition, changes in the oxidation state at the termini of the olefins have a profound effect upon site selectivity, thus leading to 3-deoxy 3-C-substituted carbohydrates, off-template branched-chain sugars, or functionalized cyclopentanes.

Heterogeneity of the early outward current in ventricular cells isolated from normal and hypertrophied rat hearts

1. The nature, magnitude and kinetics of the 4-aminopyridine-sensitive early outward current (Ito) were analysed in isolated ventricular myocytes from the septum, the apex and the left ventricular free wall of rat ventricles using the whole-cell voltage clamp method. The modulatory effect of pressure overload-induced cardiac hypertrophy on the regional variations of Ito was assessed in each topographical class of cells. 2. Voltage clamp experiments were performed at room temperature (20-25 degrees C) in the absence of Na+ on both sides of the membrane and in the presence of 3 mM CoCl2. Ito was studied from a holding potential of -80 mV and determined by subtraction of total outward currents elicited by the same protocols in the presence of 3 mM 4-aminopyridine (4-AP) from those obtained in its absence. 3. In normal hearts, membrane passive properties were very similar in each topographical class of cells. Our results confirmed that the predominant early outward current in rat ventricular cells was 4-AP-sensitive, time and voltage dependent, and demonstrated that the magnitude of the current varied on a regional basis: current density of Ito in left ventricular free wall cells (30.1 +/- 9.2 pA/pF at +60 mV) was larger than in apex cells (20.2 +/- 1.7 pA/pF) or in septum cells (11.9 +/- 3.3 pA/pF). We noticed a larger variability in data from left ventricular free wall compared with other regions. 4. No shift in steady-state voltage dependence of Ito activation and inactivation was found. However, the maximal computed chord conductances were (in microS/pF): 0.18 +/- 0.07 for left ventricular free wall cells, 0.13 +/- 0.02 for apex cells, and 0.08 +/- 0.02 for septum cells. These findings might reflect a differential distribution in functional channel densities. 5. No difference in voltage-dependent Ito activation kinetics was present with respect to topography. However, inactivation time constants in septum were longer than those of both other groups. 6. Left ventricular hypertrophy was induced by abdominal aortic constriction and its effects compared to the findings from normal rats. Hypertrophied cells had similar resting potentials but higher capacitance values than normal cells. Although Ito magnitude appeared not to be modified, the current density-voltage curves were slightly shifted to more positive potentials and significantly decreased as compared to normal cells (in pA/pF, at +60 mV): 8.4 +/- 5.0 in the left free wall group, 11.6 +/- 2.0 in the apex group, and 3.8 +/- 1.5 in the septum group.(ABSTRACT TRUNCATED AT 400 WORDS)

An 80-kilodalton antigen from Histoplasma capsulatum that has homology to heat shock protein 70 induces cell-mediated immune responses and protection in mice

An extract of the cell wall and cell membrane from Histoplasma capsulatum yeast cells was assayed by Western blot (immunoblot) for reactivity with two monoclonal antibodies to heat shock protein 70. Four bands with molecular masses of 80, 66, 54, and 32 kDa bound both antibodies. The 80-kDa protein was isolated, analyzed for homology to heat shock protein 70, and tested for antigenicity and immunogenicity in C57BL/6 mice. The 80-kDa protein reacted with monoclonal antibody to heat shock protein 70. Sera from mice immunized with the antigen recognized H. capsulatum heat shock protein 70. Moreover, the amino-terminal sequence of the 80-kDa protein revealed substantial homology with heat shock protein 70 from several species. The 80-kDa protein induced delayed-type hypersensitivity responses in mice immunized with either viable yeast cells or antigen. Splenocytes from mice immunized with yeast cells or with antigen responded in vitro to the 80-kDa antigen. Immunization of mice with the antigen enhanced host resistance against a sublethal inoculum of H. capsulatum yeast cells, but it did not reduce the mortality of mice given a lethal challenge of yeast cells. Thus, this antigen manifests homology with members of the heat shock protein 70 family. Furthermore, the 80-kDa protein elicits cellular immune responses to H. capsulatum, and it mediates protective immunity.

Protective efficacy of a 62-kilodalton antigen, HIS-62, from the cell wall and cell membrane of Histoplasma capsulatum yeast cells

We reported previously that a detergent extract of the cell wall and cell membrane of Histoplasma capsulatum yeast cells contains antigens recognized by T cells. In T-cell immunoblot analysis, a region encompassing 62 kDa was stimulatory for an H. capsulatum-reactive T-cell line and T-cell clones derived from C57BL/6 mice. In this study, we isolated a 62-kDa band, termed HIS-62, from electrophoresed cell wall and cell membrane of H. capsulatum yeast cells and examined its antigenicity and immunogenicity. C57BL/6, BALB/c, and CBA/J mice that were immunized with viable H. capsulatum yeast cells mounted a delayed-type hypersensitivity response to HIS-62 that was stronger than that of normal controls. Spleen cells from each strain of mouse immunized with viable yeast cells proliferated vigorously in response to HIS-62; conversely, splenocytes from control animals did not recognize this antigen. A T-cell line and 5 of 5 T-cell clones from C57BL/6 mice, 10 of 15 BALB/c T-cell hybridomas, and 8 of 12 CBA/J T-cell hybridomas recognized HIS-62. A cutaneous delayed-type hypersensitivity response to the antigen was apparent in each strain of mouse that was injected with 80 micrograms of HIS-62 mixed with Freund adjuvant. In addition, spleen cells from HIS-62-immunized mice proliferated in vitro in response to this antigen. Vaccination of each strain of mouse with 80 micrograms of HIS-62 conferred protection against a lethal intravenous challenge with H. capsulatum yeast cells. Thus, HIS-62 appears to be an important target of the cellular immune response to H. capsulatum and induces a protective immune response in mice.

Inhibition of the pituitary-gonadal axis by a single intramuscular administration of D-Trp-6-LH-RH (decapeptyl) in a sustained-release formulation in patients with prostatic carcinoma

For the past 6 years we used daily injection of luteinizing hormone-releasing hormone (LH-RH) agonists to treat patients with advanced prostate carcinoma. In this study we determined the hormonal response of the pituitary-testicular axis over a 2-month period and evaluated the safety and tolerance of the single intramuscular administration of sustained-release formulations of D-Trp-6-LH-RH microcapsules designed to release 50, 100, or 200 micrograms/day for over 1 month. Serum levels of LH, testosterone, and D-Trp-6-LH-RH were measured by RIA for up to 60 days in 10 patients with advanced prostatic carcinoma who had not received any previous drug therapy. After the administration of the microcapsules there was a biphasic increase in D-Trp-6-LH-RH serum levels. The maximal peak was obtained between 1 and 3 hr, and a second peak occurred between weeks 4 and 6. LH levels increased initially, with a maximal peak at 60 min, and elevated serum LH values persisted for more than 24 hr. LH levels began to fall on the second day, reaching subnormal values after 1 week. Serum testosterone rose during the first week and fell subsequently to less than 100 ng/dl. A rebound in LH and testosterone was seen about the 50th day after the microcapsule administration. Following the first week of therapy, we observed in all patients a significant decrease in bone pain, improvement in urinary flow obstruction, and a reversal of the signs of prostatism. No side effects were observed, and acceptance of the microcapsules was very good. Our results show that a single dose of D-Trp-6-LH-RH microcapsules suppresses of the pituitary-testicular axis for at least 50 days. D-Trp-6-LH-RH microcapsules facilitate the treatment and should lead to an improvement in the therapeutic response.

Allelic variants of acetylcholinesterase: genetic evidence that all acetylcholinesterase forms in avian nerves and muscles are encoded by a single gene

Two acetylcholinesterase (AcChoEase) polypeptide chains, alpha and beta, are expressed in avian nerves and muscles with apparent molecular masses of 110 and 100 kDa, respectively. We now show that individual quails express alpha, beta, or both AcChoEase polypeptide chains. By mating studies we show that the two AcChoEase polypeptides are autosomal and segregate as codominant alleles in classical Mendelian fashion. Biochemical studies of the two allelic AcChoEase polypeptides indicate that they have the same turnover number, have the same Km for acetylcholine, are immunoprecipitated to the same extent with a monoclonal anti-AcChoEase antibody, and can assemble with equal efficiency into multimeric forms. Thus there are no obvious functional differences between the two alleles. In heterozygotes, the rates of synthesis of the two polypeptides are identical, suggesting that there are no differences in expression of these two genes. Within an individual, nerves and muscles always express the same AcChoEase forms isolated from muscle indicates that all AcChoEase forms are comprised of the same allelic polypeptide chains. In contrast to the nicotinic acetylcholine receptors that appear to be encoded by complex multigene families, our studies on AcChoEase show that all forms of this important synaptic component in electrically excitable cells are encoded by a single gene. Thus differences in assembly and localization of the multiple synaptic forms of AcChoEase must arise through posttranscriptional events, posttranslational modifications of a similar AcChoEase polypeptide chain or both.

Tooth scaling and evolutionary dwarfism: an investigation of allometry in human pygmies

Gould has predicted that in rapidly dwarfed lineages the postcanine teeth exhibit a different scaling pattern than is the normal interspecific trend. His prediction of strong negative allometry has not been frequently tested in quantitative detail. Here we present results of scaling analyses of the molar teeth in African pygmies compared with other Africans of larger size and in Philippine pygmies compared with Filipinos of larger size. We find a pattern of strong negative allometry of tooth size to skull and body size in both these comparisons. This scaling pattern is explained by recourse to the developmental bases (known or inferred) of dwarfing in these populations. Body size decrease is related to low levels of the growth control substance insulin-like growth factor I (IGF-I), which does not appear to affect the size of the dentition. The implications of such developmental information for our understanding of allometric patterns in general, and dwarfing events in particular, are discussed.

Detection of histoplasmal antigens in mice undergoing experimental pulmonary histoplasmosis

A micro-ELISA assay was developed for the quantitation of Histoplasma capsulatum antigen in lungs, bronchoalveolar lavage fluid (BALF), and serum of intranasally infected mice. As little as 0.2 ng of antigen/ml could be detected. During the course of experimental histoplasmosis, immunologically intact, thymus-containing mice (nu/+) had detectable histoplasmal antigens in their lungs, serum, and BALF within 1 day of challenge. Lung, BALF, and serum antigen concentration rose to a peak 2 wk after challenge; in nu/+ mice, antigen concentration then declined through the next 2 wk. In contrast, athymic nude mice have depressed cell-mediated immunity; their antigen concentration continued to rise throughout the course of progressive, ultimately lethal, illness. Antigen concentrations correlated with quantitative cultures of the lungs and BALF. There was little cross reactivity in mice challenged intranasally with Candida albicans or Blastomyces dermatitidis. The sensitivity of this test, and the apparently minimal cross reactivity, suggest that the micro-ELISA for histoplasmal antigen might have significant clinical application in diagnosing and monitoring the course of histoplasmosis.

Murine model of paracoccidioidomycosis. Production of fatal acute pulmonary or chronic pulmonary and disseminated disease: immunological and pathological observations

A model of fatal acute pulmonary or chronic pulmonary and disseminated paracoccidioidomycosis was developed by intranasal challenge of young (3-4-week-old) mice with high doses (2.5-10 X 10(7) units) or low doses (0.1-1 X 10(7)) of yeast-phase Paracoccidioides brasiliensis. Fatal acute paracoccidioidomycosis was dose dependent; 10, 5, and 2.5 X 10(7) viable units of P. brasiliensis produced 100%, 66%, and 17% mortality, respectively, within 11 days. The pathologic picture was that of consolidation with a neutrophil infiltrate. Infection of adult (7-8-week-old) mice with even 10 X 10(7) units did not produce acute fatal paracoccidioidomycosis. The model of fatal acute paracoccidioidomycosis lends itself well to studies of therapeutic intervention. Increasing degrees of chronic pulmonary-disseminated paracoccidioidomycosis were produced by pulmonary infection of young mice with 0.1-1 X 10(7) viable units of P. brasiliensis. Although mice in all groups appeared healthy, pathology in lungs, liver, and spleen was evident at 7 and 10 weeks postinfection. Histopathologic observation revealed acinonodular granulomatous inflammation. At 12 weeks postinfection, there was evidence of less pathology, and of clearing of abscesses. In contrast to the pathology produced by 0.1 X 10(7) P. brasiliensis in young mice, no pathology evident on gross examination was produced by a similar dose in adult mice. Immunological evaluations of mice with chronic pulmonary-disseminated disease showed that spleen cells, but not lymph node cells, had significantly depressed blastogenic responses to concanavalin A (ConA) early after infection. However, at 12 weeks postinfection, when pathological examination indicated beginning resolution of infection, spleen cell responses to ConA were normal. The model of chronic disease is of interest for further immunological studies as well.