The maintenance of reproductive isolation in a mosaic hybrid zone between the fire-bellied toads Bombina bombina and B. variegata.

Mosaic hybrid zones arise when ecologically differentiated taxa hybridize across a network of habitat patches. Frequent interbreeding across a small-scale patchwork can erode species differences that might have been preserved in a clinal hybrid zone. In particular, the rapid breakdown of neutral divergence sets an upper limit to the time for which differences at marker loci can persist. We present here a case study of a mosaic hybrid zone between the fire-bellied toads Bombina bombina and B. variegata (Anura: Discoglossidae) near Apahida in Romania. In our 20 x 20 km study area, we detected no evidence of a clinal transition but found a strong association between aquatic habitat and mean allele frequencies at four molecular markers. In particular, pure populations of B. bombina in ponds appear to cause massive introgression into the surrounding B. variegata gene pool found in temporary aquatic sites. Nevertheless, the genetic structure of these hybrid populations was remarkably similar to those of a previously studied transect near Pescenica (Croatia), which had both clinal and mosaic features: estimates of heterozygote deficit and linkage disequilibrium in each country are similar. In Apahida, the observed strong linkage disequilibria should stem from an imperfect habitat preference that guides most (but not all) adults into the habitats to which they are adapted. In the absence of a clinal structure, the inferred migration rate between habitats implies that associations between selected loci and neutral markers should break down rapidly. Although plausible selection strengths can maintain differentiation at those loci adapting the toads to either permanent or temporary breeding sites, the divergence at neutral markers must be transient. The hybrid zone may be approaching a state in which the gene pools are homogenized at all but the selected loci, not dissimilar from an early stage of sympatric divergence.

Benign cementoblastoma: a case report.

The case of a 23-year-old with a benign cementoblastoma is presented. The clinicopathologic features, treatment and prognosis are discussed and a brief review of the literature is presented. Although this neoplasm is rare, the dental practitioner should be aware of the clinical features that will lead to its early diagnosis and treatment.

Nasal bilevel positive airway pressure therapy in children with a sleep-related breathing disorder and attention-deficit hyperactivity disorder: effects on electrophysiological measures of brain function.

OBJECTIVE: To examine the effect of nasal bilevel positive airway pressure (BiPAP) treatment for concurrent sleep-related breathing disorders (SRBDs) and attention-deficit hyperactivity disorder (ADHD) on electrophysiological measures of spontaneous brain activity and auditory stimulus processing. METHODS: Nineteen children diagnosed with both SRBD and ADHD participated. Electroencephalogram (EEG) activity was recorded during a resting period and an auditory oddball task before beginning BiPAP treatment, after 6 months on treatment, and after a subsequent 1 week non-treatment period. Treatment effects on EEG and event-related potentials (ERPs) to target stimuli were examined via topographic analysis. RESULTS: Thirteen of the initial 19 children completed 6 months of BiPAP therapy, with six lost mainly due to compliance problems. Children on BiPAP therapy showed a significant decrease in slow-wave (delta and theta) and an increase in fast wave (beta) EEG activity. The P3 component of the ERP showed treatment effects in amplitude and latency. CONCLUSIONS: The electrophysiological data suggest that SRBDs may contribute to ADHD symptomatology. Treatment of SRBD with BiPAP therapy in children with concurrent ADHD can lead to significant changes, in the direction of normalization, of the typical electrophysiological features of ADHD.

Drug use for the pregnant or lactating patient.

The dental patient who is pregnant or lactating may require management involving the administration or prescription of drugs. The approach of completely avoiding all drugs may not permit appropriate treatment of the patient and most often is not warranted. This article reviews the current considerations in the use of drugs in the dental patient who is either pregnant or lactating. The safety of the local anesthetics, vasoconstrictors, analgesics, antimicrobials, and sedatives used in dentistry is discussed.

Differential in vitro activation and deactivation of cysteine proteinases isolated during spore germination and vegetative growth of Dictyostelium discoideum.

Acid-activatable cysteine proteinases of Dictyostelium discoideum were first identified in spore extracts of strain SG1 using gelatin/SDS/PAGE, followed by acid treatments. Here we utilized the technique of acid activation to identify cryptic cysteine proteinases throughout auto-induced and heat-induced spore germination of D. discoideum strain SG2 and SG1. The major acid-activatable cysteine proteinase identified in SG2 and SG1 spore extracts was ddCP38 (D. discoideum cysteine proteinase with a molecular mass of 38 kDa) and ddCP48, respectively. Further investigation of these enzymes revealed that they were also base deactivatable with a treatment of ammonium chloride directly following acid activation. However, the most intriguing observation was the reversibility of the effects of base deactivation on the enzymes following a second treatment with acetic acid. Thus, we hypothesize that, unlike most mammalian cysteine proteinases which generally require the cleavage of a pro-peptide region for activation, these cysteine proteinases of D. discoideum likely undergo reversible conformational changes between latent and active forms. Moreover, we were able to detect these cryptic cysteine proteinases in the vegetative cells and early aggregates of both strains SG1 and SG2. Studies using 4-[(2S, 3S)-3-carboxyoxiran-2-ylcarbonyl-L-leucylamido]buty lguanidine, a cysteine proteinase inhibitor, revealed that acid activation of a portion of these proteinases was still achievable even after incubation with the inhibitor, further supporting the concept of two stable and reversible conformational arrangements of the enzymes. Thus, we speculate that the pH shuffles that modulate proteinase conformation and activity in vitro may be a reflection of the in vivo regulation of these enzymes via H+-ATPases and ammonia.

Management considerations for the pregnant or nursing emergency patient.

It is important to realize the risk-benefit ratio in all therapeutic modalities in any patient and that these variables vary from patient to patient as do circumstances. The emergency patient who is pregnant or nursing should not be feared or be denied appropriate treatment. It is always best to err on the side of safety and remain conservative. The dental problem can usually be treated with the use of adequate local anaesthesia and supplemental nitrous oxide in the second or third trimester. Nevertheless, situations arise that may warrant consultation with the patient's physician or specialist. This brief overview should refamiliarize the dental practitioner with the medications available to treat the gravid patient. It is important to have an understanding of our common therapeutics as well as the inherent treatment risks and benefits as they relate to the changing maternal-fetal physiology.

Adenylyl cyclase G, an osmosensor controlling germination of Dictyostelium spores.

Dictyostelium cells express a G-protein-coupled adenylyl cyclase, ACA, during aggregation and an atypical adenylyl cyclase, ACG, in mature spores. The ACG gene was disrupted by homologous recombination. acg- cells developed into normal fruiting bodies with viable spores, but spore germination was no longer inhibited by high osmolarity, a fairly universal constraint for spore and seed germination. ACG activity, measured in aca-/ACG cells, was strongly stimulated by high osmolarity with optimal stimulation occurring at 200 milliosmolar. RdeC mutants, which display unrestrained protein kinase A (PKA) activity and a cell line, which overexpresses PKA under a prespore specific promoter, germinate very poorly, both at high and low osmolarity. These data indicate that ACG is an osmosensor controlling spore germination through activation of protein kinase A.

Acid-activatable cysteine proteinases in the cellular slime mold Dictyostelium discoideum.

Studies of the cysteine proteinases of the cellular slime mold Dictyostelium discoideum have been aided by a simple acid treatment step that was incorporated into the standard one-dimensional gelatin-sodium dodecyl sulfate-polyacrylamide gel electrophoresis assay procedure. The step involved immersing the separating gel in 10% (v/v) glacial acetic acid for 30-60 s immediately after electrophoresis. This modified approach revealed the presence of acid-activatable forms of some enzymes with noticeable increases in their ability to hydrolyze gelatin, a substrate present in the sodium dodecyl sulfate-polyacrylamide gels, and peptidyl amidomethylcoumarins. The activation has been analyzed using extracts of dormant spores from which cysteine proteinase activity had previously appeared low or virtually absent. The major acid-activatable proteinase had an apparent molecular mass of 48 kDa. Its activation was not due to autocatalysis as it was not prevented by mercuric chloride, an inhibitor of the enzyme, and was not accompanied by a significant change in electrophoretic mobility. It was most likely due to a conformational change and/or the removal of a low molecular weight inhibitor. The acid treatment has also revealed the presence of acid-activatable cysteine proteinases in vegetative cells, in which cysteine proteinase activity is present at high levels, as well as among enzymes from the developmental cells which have much lower cysteine proteinase activity. Indeed novel developmental forms were detected at some stages. These results provide additional insight concerning cysteine proteinase expression at various stages during development in the slime molds. A developmental model is presented which suggests that the crypticity of the cysteine proteinases in dormant spores may be governed by proton pumps and endogenous lysosomotropic agents.

Odontogenic infections: Part two. Microbiology, antibiotics and management.

This article deals with the microbiological aspects of infections, the principles and role of antibiotic use and the general management of the patient suffering from an odontogenic infection. Clinical aspects of the most common presentations will be addressed to understand the organized management of these challenging patients. (Part one appeared in Oral Health, May, 1995).

Odontogenic infections: Part one. Anatomy and radiology.

Odontogenic infections are frequently encountered by the dentist. The signs and symptoms of these common dental emergencies are outlined in this two-part article. A thorough knowledge of the fascial planes and anatomical routes of infection spread is a critical prerequisite to understanding the clinical manifestations, potential complications, and appropriate management of these infections.

RasG protein accumulation occurs just prior to amoebae emergence during spore germination in Dictyostelium discoideum.

RasG protein levels in dormant and germinating spores of Dictyostelium discoideum strains JC1 and SG1 were estimated by Western blotting. RasG levels were very low in dormant spores and remained low during the lag period, regardless of whether spores were heat activated or treated with autoactivator during the early stages of spore germination. RasG levels increased late during spore swelling just prior to the emergence stage of germination. These data are consistent with a requirement for RasG during vegetative growth.

Fractures of the zygomatic complex: a case report and review.

Traumatic injuries to the midface are not nearly as common in Canada as they are in the United States, but practitioners must still be prepared for the evaluation and treatment of patients presenting with midface fractures. This case report demonstrates the experience one individual who presented with the clinical signs and symptoms of midfacial trauma. Cases of this nature can be confidently managed by an oral and maxillofacial surgeon. A review provides knowledge regarding anatomic features, classification schemes and the diagnostic and therapeutic decisions encountered with the treatment of zygomatic complex fractures. The forward projection of the zygoma causes it to be frequently injured secondarily to blunt trauma of the midface, at the expense of protecting the orbit.

Third ventriculostomy for shunt infections in children.

Four children with extracranial shunts for noncommunicating hydrocephalus suffered from recurrent or intractable shunt infections. All patients were resistant to or relapsed after treatment with intravenous and intrathecal antibiotics with change of the shunt apparatus. They were treated with neuroendoscopic third ventriculostomy and the removal of all implants, except for a reservoir in one patient. That child later had the reservoir removed because of persistent proteus infection. All patients received antibiotics for approximately 2 weeks after the operation. There was no morbidity associated with the procedure, and all patients remain shunt independent with follow-up periods of 21 to 46 months (mean, 33 mo), although one has needed another third ventriculostomy. We have shown that third ventriculostomy is a successful surgical intervention for the management of shunt infections in patients with noncommunicating hydrocephalus.