Estimating the size of an illicit-drug-using population

This paper describes a new method for estimating the size of an illicit-drug-using population. It is designed to overcome certain limitations of registry-based techniques that require both comprehensive site coverage and unique case identifiers, and which do not typically provide estimates of the number of drug users who are currently active. The approach involves collecting retrospective self-report data on the careers of individuals who appear at drug treatment programmes. A model is developed that corrects for the selection bias introduced by the sampling plan, and which allows us to estimate the rate at which drug users generate treatment admission events during spells of use. The size of the drug-using population is estimated by dividing the estimated total number of treatment admissions that are generated during some fixed interval of time by the estimated rate at which individuals generate such events. The technique is tested in a series of simulation studies which demonstrate that accurate estimates of the size of the drug using population can be obtained in this manner. Analytical expressions for confidence intervals about the population estimates are derived as part of the exercise. Limitations of the approach and other potential applications are discussed.     

Molecular biology and ontogeny of gamma-aminobutyric acid (GABA) receptors in the mammalian central nervous system

gamma-Aminobutyric acid (GABA) is the predominant inhibitory neurotransmitter in the mammalian central nervous system. After release from nerve terminals, GABA binds to at least two classes of postsynaptic receptors (ie, GABAA and GABAB), which are nearly ubiquitous in the brain. GABAA receptors are postsynaptic heteropentameric complexes that display unique physiologic and pharmacologic properties based on subunit composition. Activation of GABAA receptors in mature neurons results in membrane hyperpolarization, which is mediated principally by inward chloride flux, whereas in early stages of brain development, GABAA receptor activation causes depolarization of the postsynaptic membrane. GABA, receptors reside both presynaptically and postsynaptically, exist as heterodimers and are coupled to voltage-dependent ion channels through interactions with heterotrimeric G proteins. This review summarizes the molecular biology and ontogeny of GABAA and GABAB receptors, highlighting some of their putative roles during normal brain development as well as in disease states such as epilepsy.     

Ocular ischemic syndrome: long-term ocular complications

Acute retinal arterial occlusive events in the eye are generally easily recognized and the association with embolic material, often from ulcerative lesion of the ipsilateral carotid vessels, usually can be established by noninvasive imaging techniques. In contrast, chronic retinal and choroidal circulatory impairments from ophthalmic artery insufficiency is usually due to high-grade, hemodynamically-significant carotid occlusive disease which can be difficult to recognize because of the diverse clinical features and presentations. We present herein the experience of the senior author (LEM) in the diagnosis and management of these complex cases.     

Percutaneous drainage of subphrenic abscess: a review of 62 patients

Sixty-two patients who presented with subphrenic abscesses had the abscesses drained percutaneously. Diagnosis of a subphrenic collection was usually made with sonography. Initial percutaneous drainage was accomplished with a combination of sonography and fluoroscopic guidance. More recently (in the last 31 cases) most drainages were done with sonographic guidance alone. Successful catheter drainage was achieved in 85% with a complication rate of 4.8%. Failure of catheter drainage (defined as any patient who was not cured by percutaneous drainage alone) occurred in patients with multiple collections or in whom the primary cause of the abscess necessitated surgery, for example, perforated ulcer, acute cholecystitis. Considerations for successful drainage include understanding the anatomy of the subphrenic space, recognizing the importance of a correct access route (avoidance of the pleura and lung), and the long time necessary for adequate drainage (longer than 10 days in 60%). An angled subcostal approach to the subphrenic space was used in 56 (90%) of 62 cases. No complications occurred in this group. The one pneumothorax that occurred in the remaining six cases was a direct result of using an intercostal approach through the parietal pleura into a subphrenic collection. We conclude that percutaneous drainage is a safe and effective method of treatment of subphrenic abscesses.     

Microbubbles as a contrast agent for neurosonography and ultrasound-guided catheter manipulation: in vitro studies

Tissue-equivalent ultrasound phantoms, including models of the ventricular system and cyst phantoms, may be useful for developing expertise in both biopsy procedures and shunt catheter placement that use ultrasound guidance. These phantoms have been constructed (1) to assess the ability to position biopsy needles and manipulate shunt catheters with conventional angiographic guidewires and (2) to evaluate the usefulness of microbubbles as an ultrasound contrast agent. Optimal catheter and needle position and catheter patency are demonstrated with microbubbles generated by hand injection of small volumes of saline, a safe ultrasound contrast agent that, to our knowledge, has not been previously exploited in neurosonography. Microbubbles can define biopsy needle location without direct imaging of the biopsy needle; they can also define the extent of communication or separation of fluid-filled or loculated spaces.     

GABAA receptor-mediated activation of L-type calcium channels induces neuronal excitation in surgically resected human hypothalamic hamartomas.

PURPOSE: The human hypothalamic hamartoma (HH) is a rare, intrinsically epileptogenic lesion associated with gelastic seizures, but the underlying mechanisms remain unclear. Here, we examined the role of GABAA receptors in surgically resected HH tissue. METHODS: HH tissue slices (350 microm) were studied using cellular electrophysiological, calcium imaging, and immunocytochemical techniques. RESULTS: Two neuronal cell types were seen: small (10-16 microm) spontaneously firing GABAergic neurons and large (20-28 microm) quiescent neurons. In gramicidin-perforated patch recordings, muscimol (30 microM) induced membrane depolarization in 70% of large (but not small) neurons and a concomitant rise in intracellular calcium. These responses were blocked by bicuculline methiodide (50 microM). Depolarizing neurons also exhibited more positive reversal potentials (Emuscimol) and significantly higher intracellular chloride concentrations compared to those that hyperpolarized. The cation chloride co-transporters NKCC1 and KCC2 were coexpressed in the majority of large neurons, but fluorometric measurements revealed that 84% of large HH neurons expressed solely or relatively more NKCC1. Bumetanide (20 microM), a NKCC1 antagonist, partially suppressed muscimol-induced excitation in large neurons. Concordant with robust expression of CaV1.2 and CaV1.3 subunits in HH neurons, the L-type calcium channel blocker nifedipine (100 microM) prevented muscimol-induced neuronal excitation. CONCLUSIONS: GABAA receptor-mediated excitation, due in part to differential expression of NKCC1 and KCC2 and subsequent activation of L-type calcium channels, may contribute to seizure genesis in HH tissue. Given the ready availability of L-type calcium channel blockers, our results have clinical ramifications for the treatment of seizures associated with HH lesions.     

Renal cell carcinoma associated with incidental presentation of renal artery aneurysm: surgical management

The Renal Artery Aneurysm (RAA) is a relatively uncommon vascular lesion. A renal artery disease coexisting in patients with Renal Cell Carcinoma (RCC) is an even more infrequent clinical presentation. We reported on the treatment of a rare case of incidentally intraoperative renal artery aneurysm discovered during a nephron-sparing surgery for RCC. After the surgery the patient did not need hypertension therapy any longer. This event is well-known, in fact a number of possible contributions to a renin-mediated hypertension management has been postulated.