Double-labelling with rhodamine beads and biocytin: a technique for studying corticospinal and other projection neurons in vitro

Corticospinal neurons retrogradely labelled with rhodamine-labelled latex microspheres (RLMs) in vivo were studied intracellularly in a slice preparation up to 13 months later with electrodes containing biocytin. The physiological properties of these double-labelled corticospinal neurons were indistinguishable from those of comparable neurons which were impaled with biocytin-containing electrodes without prior RLM-labelling, and neurons studied with potassium acetate-filled electrodes in similar areas. Thus, neither labelling with RLMs nor injection of biocytin affected neuronal properties. This important advantage of RLMs makes them suitable for prelabelling projection neurons in vivo for subsequent studies that take advantage of the versatility of a brain slice preparation. In addition to its lack of effects on neuronal properties, intracellular labelling with biocytin also provides high-quality morphological details ideal for anatomical analysis. The compatibility of retrograde labelling with RLMs and intracellular staining with biocytin make this a useful combined technique for tracking electrophysiological and anatomical changes in identified projection neurons over time.     

Ventromedial hypothalamus vs. lateral hypothalamic D2 satiety receptors in the body weight increase induced by systemic sulpiride

Two experiments were conducted in order to see if dopamine satiety receptors in the lateral hypothalamus or satiety mechanisms in the ventromedial hypothalamus were involved in the hyperphagia and body weight increase induced by systemic sulpiride. In the first experiment, it was shown that systemic sulpiride (20 mg/kg) does not block the anorexia caused by intraperifornical injections of amphetamine. In the second experiment, sulpiride (20 mg/kg during 18 days) did not produce an additional increase in body weight in previously VMH-lesioned female rats. This last fact cannot be explained by a ceiling effect since insulin (5 U/day during 7 days) increased body weight in the same VMH rats in which sulpiride was not effective. These results do not support the hypothesis that systemic sulpiride reaches the perifornical dopamine D2 receptors to disinhibit feeding, but suggest instead an involvement of the ventromedial hypothalamus. This last suggestion is more in agreement with the hypothesis that sulpiride alters feeding and body weight gain through the induction of a functional gonadectomy.     

The O-methylated derivative of L-DOPA, 3-O-methyl-L-DOPA, fails to inhibit neuronal and non-neuronal aromatic L-amino acid decarboxylase

The present study examined whether the O-methylated derivative of L-DOPA, 3-O-methyl-L-DOPA (3-OM-L-DOPA), inhibits neuronal (brain) and non-neuronal (liver and kidney) aromatic L-amino acid decarboxylase (AADC) activity. The incubation of brain, liver and kidney homogenates with 3-OM-L-DOPA (5 mM) did not result in the formation of 3-methoxytyramine, the compound expected to result from the decarboxylation of 3-OM-L-DOPA. Incubation of tissue homogenates with L-DOPA resulted in a concentration-dependent formation of dopamine, revealing K(m) values (in mM) of similar magnitude for brain (0.8), liver (1.6) and kidney (1.0). Both benserazide and L-5-hydroxytryptophan (L-5-HTP) were found to produce concentration dependent decreases in AADC activity with K(i) values in the microM range. By contrast, 3-OM-L95% reduction) in liver and kidney AADC activity accompanied by a marked decrease (49% reduction) in brain AADC activity. By contrast, the administration of 30 mg/kg (p.o.) 3-OM-L-DOPA, which generates levels in brain, liver and kidney six-fold those in L-DOPA-treated rats, was found to change neither neuronal nor non-neuronal AADC activity. In conclusion, 3-OM-L-DOPA fails to interact with neuronal and non-neuronal AADC, either as substrate or inhibitor.     

Current management of calculi in horseshoe kidneys

OBJECTIVES: To assess treatment options for calculi in horseshoe kidneys and the impact of extracorporeal shockwave lithotripsy (ESWL) on the management of renal stones. MATERIAL AND METHODS: From June 1971 to January 1998, 52 patients with horseshoe kidneys and calculi received treatment at our Urologic Stone Unit. There were 40 men (77%) and 12 women (23%). Average patient age was 41 years (range: 10-70 years). Clinical onset, treatment received and outcome were evaluated retrospectively. A successful outcome was defined as a patient without residual calculi or with fragments <0.4 cm in size. RESULTS: Clinical onset was mainly low back pain in 37 patients (71%). Eighty-nine stones were treated, i.e. an average of 1.7 treatments per patient. Before the ESWL era (May 1987), we performed two heminephrectomies, 16 pyelolithotomies, 12 pyelolithotomies combined with ureteropyeloplasty and one percutaneous nephrolithotomy. Since the advent of ESWL, seven pyelolithotomies and three pyelolithotomies combined with ureteropyloplasty have been done. ESWL was used to treat 48 calculi. In three cases the patient was placed in the prone position due to difficulties in stone focusing. In 37 cases (77%) patients were either rendered stone-free or had residual fragments <0.4 cm in size. Urinary diversion for obstruction was carried out in two cases (4%). CONCLUSIONS: At present ESWL is the first-choice treatment for calculi in horseshoe kidneys. It involves no significant focusing difficulties and is associated with a low incidence of obstructive complications. Open surgery is indicated in cases of stone-related pyeloureteral stenosis and in the presence of calculi >2-2.5 cm in size.