Male quality, signal reliability and female choice: assessing the expectations of inter-sexual selection.

Numerous models have attempted to explain the evolution of extravagant male ornaments found in many species. Inter-sexual indicator models postulate that male ornaments evolved as signals of quality, and that females use these signals to select the highest quality males. These models involve three traits--male quality, male signals and female preferences--and have specific expectations about the relative strengths of the phenotypic relationships between these traits. Using data from anuran species, we assessed the relative strengths of the phenotypic relationships using meta-analysis. The relative strengths of these phenotypic correlations were as expected by indicator models, providing support for indicator models of inter-sexual selection. We also found much variation in our data, suggesting that additional, untested factors may mediate inter-sexual interactions in this taxon, such as differences in the importance of quality signalling between species. These factors require investigation, in order to improve our understanding of inter-sexual selection.

Antigen-driven B cell differentiation in vivo.

The secretion of specific antibodies and the development of somatically mutated memory B cells in germinal centers are consequences of T cell-dependent challenge with the hapten (4-hydroxy-3-nitrophenyl)acetyl (NP). Using six-parameter flow cytometry and single cell molecular analysis we can directly monitor the extent of somatic hypermutation in individual responsive (isotype switched) antigen-specific B cells. The current study provides a direct quantitative assessment of recruitment into the antibody-secreting compartment on the one hand, and the germinal center pathway to memory on the other. Cellular expansion in both compartments is exponential and independent during the first week after challenge. The first evidence of somatic mutation, towards the end of the first week, was restricted to the germinal center pathway. Furthermore, germinal center cells express a significantly shorter third hypervariable region (CDR3), even when unmutated, than their antibody-secreting counterparts, suggesting a secondary selection event may occur at the bifurcation of these two pathways in vivo. By the end of the second week, the majority of mutated clones express a shorter CDR3 and affinity-increasing mutations as evidence of further selection after somatic mutation. These data provide evidence for substantial proliferation within germinal centers before the initiation of somatic mutation and the subsequent selection of a significant frequency of mutated clonotypes into the memory compartment.

Electrophysiological recordings from spontaneously contracting reaggregates of cultured smooth muscle cells from guinea pig vas deferens.

Smooth muscle cells were enzymatically dispersed from vasa deferentia of adult male guinea pigs (250-400 g). These cells reassociated in vitro to form monolayers and small spherical reaggregates (0.05-0.3 mm in Diam). Within 48 h of being placed in culture, cells in both types of preparation began to contract spontaneously. The contractions were rhythmic and slow. Cells in the monolayers stopped contracting after approximately 1 wk in vitro, but the reaggregates continued to contract spontaneously for at least 3 wk. Electron microscopy of the reaggregates revealed the presence of thick and thin myofilaments. Overshooting action potentials were recorded in many of the cells penetrated (primarily in reaggregates), and were accompanied by visible contractions of the aggregate or monolayer. Quiescent cells could often be excited by intracellularly applied depolarizing and hyperpolarizing (anodal-break) current pulses. The resting potentials had a mean value of -58 +/- 2 mV. The action potentials were usually preceded by a spontaneous depolarization. The action potentials had slow rates of rise (1--4 V/s) which were unaffected by tetrodotoxin (TTX, 1 microgram/ml), a known blocker of fast Na+ -channels. Verapamil (1 microgram/ml) blocked the action potentials. The mean value of input resistance was 6.9 +/- 0.5 M omega (n = 12). These electrophysiological properties are similar to those of intact adult vas deferens smooth muscle cells. Thus, the cultured adult vas deferens smooth muscle cells retain their functional properties in vitro even after long periods.

Messenger RNA induction of fast sodium ion channels in cultured cardiac myoblasts.

Incubation with adult heart messenger RNA caused the appearance of fast sodium ion channels in young myocardial cells whose development has been arrested in vitro. The induction was blocked by cycloheximide, indicating dependence on protein synthesis. Thus, cardiac myoblasts can be made to differentiate in vitro, and membrane properties can be altered by exogenous RNA.

Inhibition of aromatase expression by a psoralen-linked triplex-forming oligonucleotide targeted to a coding sequence.

The cytochrome P450 enzyme aromatase (P450arom) is an important target in breast cancer treatment. We have designed a 20-base pyrimidine oligodeoxynucleotide (ODN) which forms a sequence-specific triple helix (triplex) with a purine-rich tract in the P450arom coding sequence. The psoralen-linked ODN (Pso20T) formed photo-induced cross-linked products with target double-stranded DNA. Cross-linked adducts formed in vitro between ODNs and P450arom expression constructs were used to transfect COS and human MCF-7 breast cancer cells. Levels of aromatase transcripts and enzyme activity were significantly lower in cultures transfected with Pso20T-treated cDNA relative to controls. Pso20T had a lesser inhibitory effect on aromatase expression from a mutant P450arom construct, consistent with predicted effects of the mutations on triplex formation. These results are compatible with triplex-mediated interruption of transcription within intact cells.

The Marinesco-Sjögren syndrome examined by computed tomography, magnetic resonance, and 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography.

The Marinesco-Sjögren syndrome is an autosomal recessive degenerative disorder characterized by congenital cataracts, cerebellar ataxia, spasticity, mental deficiency, and skeletal abnormalities. We studied two adult siblings with Marinesco-Sjögren syndrome using anatomic and metabolic brain imaging techniques to characterize the pattern and nature of abnormalities in the brain. Computed tomographic and magnetic resonance imaging showed diffuse brain atrophy of mild to moderate degree, involving primarily the white matter of the cerebrum, cerebellum, brain stem, and cervical spinal cord. The pattern of atrophy resembled that seen in diffuse leukoencephalopathies. Measurements of local cerebral glucose metabolic rates with positron emission tomography revealed no statistically significant differences from normal control subjects in most regions, but metabolic rate was decreased in the thalamus in one patient. The findings support a diffuse white matter disorder in Marinesco-Sjögren syndrome.

Clinical pharmacokinetics of gabapentin.

Pharmacokinetic properties are important to consider in evaluating the usefulness of new antiepileptic drugs (AEDs). Gabapentin is a new, water-soluble, antiepileptic agent with properties of an amino acid. This drug is rapidly absorbed and exhibits dose-dependent bioavailability as a result of a saturable transport mechanism. Plasma concentrations are essentially proportional to dosages up to 1,800 mg daily, which is the highest dosage used in double-blind, placebo-controlled clinical trials. Gabapentin is not protein-bound. A high volume of distribution indicates greater concentration in tissue than in plasma. It is not metabolized and does not induce hepatic enzymes or inhibit metabolism of other antiepileptic drugs. As a result, metabolism-related factors do not necessitate dosage alterations of gabapentin and concomitant AEDs after prolonged therapy. The drug is excreted unchanged in urine; plasma clearance is linearly related to creatinine clearance; and dosage is readily adjusted based on renal function. The elimination half-life is approximately 5 to 9 hours. Consequently, three divided doses are usually required per day, but steady state is rapidly achieved. No significant interactions between gabapentin and standard antiepileptic drugs or oral contraceptives have been observed. These and other pharmacokinetic properties make gabapentin unique among available AEDs.

Fatal familial insomnia: clinical and pathologic heterogeneity in genetic half brothers.

We describe clinical and pathologic features of a patient with fatal familial insomnia (FFI) whose prion (PrP) genotype is D178N coupled with methionine at codon 129 on his mutant allele and valine at codon 129 on his normal allele. A cousin (genetic half brother) with identical PrP genotypes exhibited strikingly different clinical and pathologic changes. Comparison of these cousins shows the phenotypic heterogeneity of FFI and suggests that the phenotypic expression of D178N is influenced by multiple factors.

A PrP gene codon 178 base substitution and a 24-bp interstitial deletion in familial Creutzfeldt-Jakob disease.

Several mutations in the prion protein (PrP) gene are associated with familial Creutzfeldt-Jakob disease (FCJD). We describe a family in which five members in three generations have had FCJD. The proband and some descendants of the affected members carried an abnormal PrP gene allele. This allele contained a 24-bp deletion from the tandem repeat region of the open reading frame and a codon 178 missense substitution. Observations suggest that the codon 178 mutation is involved in the pathogenesis of FCJD in the family described here. The 24-bp deletion may be an uncommon polymorphism.

Synthesis and antiviral activity of (E)-5-(2-bromovinyl)uracil and (E)-5-(2-bromovinyl)uridine.

(E)-5-(2-Bromovinyl)uracil (BVU) and (E)-5-(2-bromovinyl)uridine (BVRU) were synthesized starting from 5-formyluracil via (E)-5-(2-carboxyvinyl)uracil or starting from 5-iodouridine via (E)-5-(2-carbomethoxyvinyl)uridine and (E)-5-(2-carboxyvinyl)uridine, respectively. Depending on the choice of the cell system, BVU and BVRU exhibited a marked activity against herpes simplex virus type 1 (HSV-1) in vitro. Although BVU and BVRU were less potent than the reference compound (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), their antiviral activity spectrum was remarkably similar to that of BVDU. The latter findings suggest that BVU and BVRU are metabolically converted to BVDU or a phosphorylated product thereof. In vivo, BVU protected mice against a lethal disseminated HSV-1 infection.

Prognostic factors in small malignant melanomas of choroid and ciliary body.

Two hundre seventeen small malignant melanomas, each with a volume less than 1,400/cu mm, were studied to determine what factors were useful in predicting metastasis. Using a single-factor approach with 16 risk factors, we found seven that correlated well with outcome. These were cell type, pigmentation, size (largest dimension), scleral extension, mitotic activity, location of anterior margin of the tumor, and optic nerve extension. Using a linear discriminant function, the four best factors in combination were cell type, largest dimension, scleral extension, and mitotic activity. Four variables (largest diameter, location of anterior margin, mitotic activity, and optic nerve invasion) that might be correlated with clinical observations were found to be less accurate in separating fatal and nonfatal cases than cell type alone.

Diazepam and its anomalous p-chloro-derivative Ro 5-4864: comparative effects on mouse neurons in cell culture.

The actions of diazepam and its p-chloro-derivative Ro 5-4864 were compared on mouse spinal cord and dorsal root ganglion neurons in cell culture. Diazepam enhanced but Ro 5-4864 reduced iontophoretic GABA responses in a concentration-dependent manner. Both diazepam and Ro 5-4864 limited sustained, high frequency repetitive firing of spinal cord neurons but diazepam was more potent. Ro 5-4864 was, however, more potent than diazepam in inhibiting spontaneous neuronal activity of spinal cord neurons and reducing the duration of calcium-dependent action potentials of dorsal root ganglion neurons. The differing actions of diazepam and Ro 5-4864 may account for the contrasting pharmacological spectra of the two benzodiazepines.

Effect of temperature on limitation by MK-801 of firing of action potentials by spinal cord neurons in cell culture.

The anticonvulsant, MK-801, limited sustained high frequency repetitive firing of sodium-dependent action potentials by mouse spinal cord neurons in monolayer dissociated cell culture. Limitation was voltage- and temperature-dependent and was accompanied by decreasing rate of rise of action potentials until firing ceased during the 400 ms depolarizations. The IC50 for limitation was 2 x 10(-7) M at 37 degrees C, 6.4 x 10(-7) M at 35 degrees C, and 4 x 10(-5) M at 23 degrees C. The relationship between the percentage of neurons capable of sustained repetitive firing and MK-801 concentration at 33 degrees C was biphasic. The first phase (about 50%) of limitation had IC50a = 1.5 x 10(-7) M, and the second had IC50b = 2 x 10(-4) M; the midpoint of the connecting plateau was 10(-5) M. At temperatures below 37 degrees C, the current needed to achieve maximal firing increased. The maximal rate of rise, maximal firing frequency and sensitivity to MK-801 of action potentials elicited by 1 ms stimuli decreased at temperatures below 37 degrees C. Passive membrane properties were unchanged. Slow firing and a temperature-sensitive conformational change in voltage-activated sodium channels could account for the higher concentrations of MK-801 required to block sodium-dependent action potentials at temperatures below 37 degrees C.

Effects of oxcarbazepine and 10-hydroxycarbamazepine on action potential firing and generalized seizures.

The anticonvulsant compound oxcarbazepine and its principal 10-monohydroxy metabolite protected potently against electroshock-induced tonic hindlimb extension. Maximal plasma concentrations depended on dose and were reached < or = 1 h after an oral dose of oxcarbazepine and < 2 h after monohydroxy derivative. In mice, the ED50 was 14 mg/kg for oxcarbazepine and 20.5 mg/kg for the monohydroxy derivative, p.o. In rats, the ED50 was 13.5 mg/kg for oxcarbazepine and 17.0 mg/kg for monohydroxy derivative, p.o. This protective effect compared favorably with the efficacy of carbamazepine, phenytoin, phenobarbital and diazepam in the same test. As observed previously, valproate and ethosuximide were markedly less potent. The effect of oxcarbazepine and its monohydroxy derivative on sustained high frequency repetitive firing of sodium-dependent action potentials of mouse spinal cord neurons in cell culture was also examined using intracellular recording techniques. Both compounds reduced the percentage of neurons capable of sustained action potential firing in concentration-dependent manner. The EC50 for oxcarbazepine was 5 x 10(-8) M and that for monohydroxy derivative was 2 x 10(-8) M (P > 0.05 vs. oxcarbazepine). For comparison, the EC50 for carbamazepine was significantly higher (6 x 10(-7) M, P < 0.001 vs. oxcarbazepine and monohydroxy derivative). Limitation of firing by oxcarbazepine and the monohydroxy derivative depended on firing frequency and membrane potential and was enhanced by depolarization. Input resistance and resting membrane potential were not altered by either drug. The in vitro effect on action potential firing frequency occurred at concentrations below plasma levels of oxcarbazepine and monohydroxy derivative which protected animals against electroshock and were therapeutically effective in patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Limitation by gabapentin of high frequency action potential firing by mouse central neurons in cell culture.

The investigational anticonvulsant drug, gabapentin (GP; 1-(aminomethyl) cyclohexaneacetic acid) limited repetitive firing of sodium-dependent action potentials of mouse spinal cord and neocortical neurons in monolayer dissociated cell culture. The effect developed slowly over time with sustained exposure. The IC50 was 1.3 x 10(-4) M for exposure times < or = 60 s, 1.9 x 10(-5) M for 10-60 min, and 4.0 x 10(-6) M for 12-48 h. Hyperpolarization restored sustained firing in the continuing presence of GP. Blockade of action potential firing by GP was frequency (use)-dependent. After preincubation with 2.9 x 10(-5) M GP (5 micrograms/ml), trains of brief stimuli at > or = 50 Hz elicited fewer action potentials than in control solution. Also, at 150 Hz, maximal rate of rise of action potentials decreased progressively with repetitive firing in GP-containing, but not control, solution. After overnight incubation in 2.9 x 10(-5) M GP, the absolute refractory period was prolonged from 2.4 +/- 0.6 ms in control solution (n = 11) to 4.7 +/- 0.3 ms (n = 10; P = 0.02 vs. control), and complete recovery from inactivation was prolonged from 8.0 +/- 1.3 ms to 17.0 +/- 2.6 ms (P < 0.001 vs. control). These findings suggest that GP may alter function of voltage-activated sodium channels, but the mechanism is unproven and may be indirect. Limitation of firing was observed in > or = 50% of neurons at concentrations in the range of those found in plasma and cerebrospinal fluid of patients treated successfully with GP. These results suggest that limiting the rate of firing of sodium-dependent action potentials may contribute to the anticonvulsant efficacy of gabapentin.

Remacemide HCl and its metabolite, FPL 12495AA, limit action potential firing frequency and block NMDA responses of mouse spinal cord neurons in cell culture.

The novel anticonvulsant, remacemide HCl [(+/-)-2-amino-N-(1-methyl-1,2-diphenylethyl)acetamide monohydrochloride; FPL12924AA], and a desglycinated metabolite [(+/-)-1-methyl-1,2-diphenylethylamine monohydrochloride; FPL 12495AA] reversibly limited sustained high-frequency repetitive firing (SRF) of sodium-dependent action potentials by mouse spinal cord neurons in monolayer dissociated cell culture. Limitation occurred with an IC50 of 7.9 X 10(-6) M for remacemide and 1.2 X 10(-6) M for FPL 12495AA (P < 0.05 vs. remacemide). Stereoisomers of the desglycinate limited SRF with IC50 values of 3.3 X 10(-6) M and 3.5 X 10(-6) M for the S(+) and R(-) compounds, respectively. The concentration of racemic desglycinate and of either stereoisomer that produced limitation in all neurons tested was 10(-4) M. Maximal rate of rise (Vmax) of action potentials decreased progressively until firing ceased during 400-ms depolarizing pulses. Efficacy of remacemide, but not of the desglycinate, increased with time (maximum at 16-36 h). The limitation was voltage dependent. In addition, reduction of Vmax and action potential failure occurred during stimulation with 400-ms pulses and trains of brief (1 ms) depolarizations at different frequencies. These findings suggest an effect on voltage-sensitive sodium current that generates the action potential upstroke. Remacemide and the desglycinate also significantly reduced the amplitude of neuronal responses to pressure application of NMDA in use-dependent manner at concentrations equal to the IC50 values for limitation of action potential firing. Resting potential and input resistance were not changed significantly by either drug. Limitation of high-frequency firing of action potentials by both remacemide HCl and FPL 12495AA may contribute to the anticonvulsant efficacy of these compounds at concentrations overlapping the range required to block glutamatergic hyperexcitability.

A static magnetic field modulates severity of audiogenic seizures and anticonvulsant effects of phenytoin in DBA/2 mice.

RATIONALE: In a search for potential supplements or alternatives to the pharmacological treatment of epilepsy, we examined the effects of static magnetic fields on audiogenic seizures of DBA/2 mice. METHODS: Two strains of DBA/2 mice were subjected to auditory stimulation that resulted sequentially in wild running, loss of righting, clonus, tonic hindlimb extension, and death in 80-95% of animals in different experiments. The incidence of seizure stages in groups of animals pretreated with a static magnetic field, phenytoin (PHT) or both was compared to the incidence in sham-exposed control mice. RESULTS: Depending on magnetic flux density and duration of exposure to the field, seizure severity decreased significantly, but not completely, in both strains. However, incidence of five seizure stages was reduced in one strain, with about half of the mice seizure free. Two seizure stages (tonic hindlimb extension and death) were reduced significantly in the other. Magnetic field pretreatment potentiated the effect of PHT. Clonic seizures refractory to PHT or magnetic field pretreatment in DBA/2J mice responded to pretreatment with a combination of PHT and the magnetic field. CONCLUSIONS: A static magnetic field had some anticonvulsant effects when employed alone. More robust effects were seen in combination with PHT. Further testing of magnetic fields for anticonvulsant effects and elucidation of mechanisms of action seem to be warranted.

Ralitoline (CI-946) and CI-953 block sustained repetitive sodium action potentials in cultured mouse spinal cord neurons and displace batrachotoxinin A 20-alpha-benzoate binding in vitro.

Ralitoline and CI-953 are anticonvulsant compounds active in both maximal electroshock and kindling models of seizures with rodents. CI-953 (IC50 = 5 microM) and ralitoline (IC50 = 2 microM) both blocked sustained repetitive firing of sodium action potentials with effects on firing activity triggered by spontaneous excitatory postsynaptic potentials at higher concentrations. No effects on iontophoretic GABA and glutamate responses were noted. Both compounds inhibited the binding of tritiated batrachotoxinin A 20-alpha-benzoate ([3H]BTX-b) to rat brain synaptosomes with apparent Kd values of 29 microM (CI-953) and 25 microM (ralitoline). Our results suggest that effects on voltage-dependent sodium channels may underlie the anticonvulsant action of these compounds.

Anticonvulsant drugs: mechanisms of action.

A variety of the anticonvulsant drugs, including carbamazepine, phenytoin, primidone, phenobarbital, clonazepam, valproic acid, and ethosuximide, are available for use in the treatment of patients with seizure disorders. These anticonvulsants vary in their efficacy against experimental seizures in animals and against seizures in humans. The mechanistic basis for this variability in anticonvulsant drug action remains uncertain, but numerous mechanisms of action have been proposed. We have used mouse neurons in primary dissociated cell culture to study the action of these anticonvulsant drugs on several aspects of membrane excitability and synaptic transmission. We have proposed that the anticonvulsant drugs can be classified according to their actions on sustained high frequency repetitive firing (SRF) of action potentials and on postsynaptic gamma-aminobutyric acid (GABA) responses. Phenytoin and carbamazepine were both effective against SRF but did not modify postsynaptic GABA responses at therapeutically relevant concentrations. Phenobarbital, benzodiazepines, and valproic acid modified both SRF and postsynaptic GABA responses. Ethosuximide had no effect on SRF or GABAergic mechanisms. Based on these results, we have proposed that blockade of SRF may underlie the action of phenytoin, carbamazepine, phenobarbital, valproic acid, and benzodiazepines against generalized tonic-clonic seizures in humans and maximal electroshock seizures in animals. Enhancement of GABAergic synaptic transmission may underlie efficacy of benzodiazepines and valproic-acid drugs against generalized absence seizures in humans and pentylenetetrazol-induced seizures in experimental animals. The mechanism of action of ethosuximide against generalized absence seizures in humans and pentylenetetrazol-induced seizures in experimental animals may be by a third, as yet unknown, mechanism.

Static magnetic field therapy for pain in the abdomen and genitals.

Two adolescents with debilitating, medication-resistant, chronic pain of the low back and abdomen with intermittent pain of the genitalia were diagnosed with intervertebral disk disease at spinal cord levels that correlated with their signs. Both patients had undergone multiple evaluations by physicians of different specialties and both underwent appendectomy without relief of their pain. The history of the onset of pain was important in determining the affected levels. The pain of both individuals was mimicked and localized by percussion of the vertebral spines at the level of disk protrusion. This maneuver and careful review of the history were important in making the correct diagnosis in each case. In both patients, treatment with novel magnetic devices provided rapid relief that was sustained for more than 2 years. These cases highlight the need for careful evaluation and correct diagnosis of abdominal and genital pain in young patients to avoid costly and unnecessary medical intervention and the stigma of painful debility.