Administering copper reduces hyper-excitability generated by penicillin G in motor cortex neurons from rat brain slices.

Recording synaptic activity of layer III neurons from motor cortex slices, which was provoked by stimulating layer IV, generated synaptic responses of the field potential (FP) that went from mean 100 µV to 600 µV when the stimulus was increased up to twice the threshold. Administering 100 µM or 200 µM of copper, increased the responses to mean 800 µV and 820 µV, respectively. The response to 200 µM was not significantly greater than that to 100 µM. However, all FP responses were significantly lower to a copper concentration of 500 µM. The basal FP was slowly restored by removing the copper with Krebs-Ringer(K-R), resulting in similar characteristics to those observed before copper administration. Then, neurons were perfused with penicillin (2000 UI) to increase cortical excitability and to assess the depressing effect of high concentrations of copper. Administering 500 µM of copper significantly reduced the activity generated by penicillin, while removing by wash(K-R) penicillin and copper generated FP responses similar to those obtained at baseline. Our data indicate that depending on the concentration, copper can behave as an activating or blocking agent for cortical activity.

Trigger point evaluation in migraine patients: an indication of peripheral sensitization linked to migraine predisposition?

Although migraine is a neurovascular disorder, both scalp tenderness and referred pain have been observed in migraine patients. The present study was carried out to investigate the presence of trigger points eliciting referred pain in 98 migraine patients and in 32 healthy subjects. Trigger points were found in 92 (93.9%) migraineurs and in nine (29%) controls (P < 0.0001). The number of individual migraine trigger points varied from zero to 14 (modal number: 4), and was found to be related to both the frequency of migraine attacks (P < 0.0001), and the duration of the disease (P = 0.017). About 74% of the total detected trigger points were found in temporal and/or suboccipital areas; other locations were mainly found in patients showing more than four trigger points. Trigger point palpation provoked a migraine attack in 30 (30.6%) patients. Pericraneal allodynia was found in 15 (15.3%) patients. These data indicate that nociceptive peripheral sensitization is a usual finding in migraine, and that central sensitization can develop in patients with frequent attacks and long-lasting disease. Trigger points' detection in migraine patients could be useful when applying therapies like acupuncture, needling or botulinum toxin injections directed to reduce peripheral sensitization.

A simple infection model using pre-colonized implants to reproduce rat chronic Staphylococcus aureus osteomyelitis and study antibiotic treatment.

Staphylococcus aureus biofilms formed on medical implants represent a serious problem, being difficult to eradicate with antibiotic therapy and leading to chronic infections. Simplified in vivo and in vitro antibiotic susceptibility assays using biofilm bacteria are needed. In this work, a novel chronic osteomyelitis infection model was developed in rats in the absence of bacterial suspension, requiring the use of only 10(6) bacteria in biofilms at the site of surgery, with a full success in reproducing infection. Stainless-steel implants pre-colonized for 12 h with a highly adherent S. aureaus isolate were introduced into the rat tibiae. In animals not submitted to antibiotic treatment, infection was found in the implants and spread to bone in all cases, indicating the high efficacy of the model to reproduce osteomyelitis. The effect of a 21-day treatment with cefuroxime, vancomycin, tobramycin or ciprofloxacin on infection was studied in this model 42 days after surgery. Bone colonization was inhibited by vancomycin and cefuroxime. Cefuroxime (the most efficient antibiotic, able to sterilize 1 out of 8 implants) reduced the number of bacteria in biofilms adhered to implants at a higher extent than vancomycin, trobramycin and ciprofloxacin. Analogous observations were made in this work in vivo and in vitro on the relative antibiotic efficacy against S. aureus biofilm bacteria. suggesting the usefulness of both tests as a potential tool to study antibiotic suceptibility, and the need for new antimicrobials against these bacteria.

Antibiotic susceptibility assay for Staphylococcus aureus in biofilms developed in vitro.

Four slime-producing isolates of Staphylococcus aureus were used in an antibiotic susceptibility assay for biofilms developed on 96-well polystyrene tissue culture plates. The study involved 11 antibiotics, two biofilm ages (6 and 48 h), two biofilm growth media (tryptone soy broth (TSB) and delipidated milk) and three antibiotic concentrations (4 x MBC, 100 mg/L and 500 mg/L). ATP-bioluminescence was used for automated bacterial viability determination after a 24 h exposure to antibiotics, to avoid biofilm handling. Under the conditions applied, viability in untreated biofilms (controls) was lower when biofilm growth was attempted in milk rather than in TSB. Various antibiotics had a greater effect on viability when used at higher (> or =100 mg/L) antibiotic concentrations and on younger (6 h) biofilms. Increased antibiotic effect was observed in milk-grown rather than TSB-grown biofilms. Phosphomycin and cefuroxime, followed by rifampicin, cefazolin, novobiocin, vancomycin, penicillin, ciprofloxacin and tobramycin significantly affected biofilm cell viability at least under some of the conditions tested. Gentamicin and erythromycin had a non-significant effect on cell viability. Transmission electron microscopy revealed that cells at the inner biofilm layers tend to remain intact after antibiotic treatment and that TSB-grown biofilms favoured a uniformity of cell distribution and increased cell density in comparison with milk-grown biofilms. A reduced matrix distribution and enhanced cell density were observed as the biofilm aged. The S. aureus biofilm test discriminated antibiotics requiring shorter (3 h or 6 h) from those requiring longer (24 h) exposure and yielded results which may be complementary to those obtained by conventional tests.

The superior colliculus, a neuronal network resistant to the Gaba withdrawal syndrome.

Chronic intracortical perfusion of GABA (Gamma Amino Butyric Acid) and its subsequent withdrawal generates the GABA withdrawal syndrome (GWS). This particular epileptic model has been observed in the motor cortex of monkeys and rats. Our purpose was to study the GWS in the motor cortex (MC), dorsal hippocampus (DH), and superior colliculus (SC). Thirty chronically-implanted adult Wistar rats were separated into 3 groups of 10 (8 experimental and 2 controls). The first group received GABA in MC, the second in the DH and the third in the SC. GABA was released in doses of 10 to 60 micrograms/microliter/h for 6 days employing osmotic mini-pumps. Two control rats per group received saline solution in the above-mentioned structures. Rats perfused in the MC showed GWS after interruption of the GABA flow. The group perfused in the DH showed paroxysmal discharges and epileptic seizures during perfusion. They also later showed GWS. No epileptic effects were observed in the SC-perfused group during either the GABA perfusion or during withdrawal. None of the six control animals showed epileptic effects. Our results show that the SC offers a strong resistance to GWS. This could be explained by the particular neuronal network structure of rat SC.

Noradrenaline mediates paradoxical effects on rat neocortical neurons after GABA withdrawal.

1. The aim of the present study was to determine the role of noradrenergic neurotransmission in neuronal activities intracellularly recorded in neocortical slices obtained from rats presenting the gamma-aminobutyric acid (GABA) withdrawal syndrome (GWS), a focal epilepsy consecutive to the interruption of a chronic intracortical GABA infusion into the somatomotor cortex. Neurons recorded in the epileptic focus area (n = 52) were bursting or nonbursting cells. Intrinsic bursting (IB, n = 20) cells presented bursts of action potentials (APs) to an intracellular depolarizing current injection and paroxysmal depolarization shifts (PDSs) to white matter stimulation. Synaptic bursting (SB, n = 22) cells presented only PDSs. Nonbursting (NB, n = 10) cells presented no burst after either synaptic stimulation or depolarizing current injection. Results were compared with those obtained from NB neurons (n = 4) recorded in slices from saline-infused rats. 2. In all of the recorded neurons, bath application of norepinephrine (NE, 10 and 100 microM) provoked a depolarization (1-5 mV) associated with a decrease in input K+ conductance having a mean reversal potential at -90 to -102 mV, not significantly different for bursting and nonbursting cells. This reversal potential differed from that of Cl(-)-mediated inhibitory postsynaptic potentials (-70 mV) elicited in NB cells by electrical stimulation of the white matter. 3. In IB cells, the NE-induced depolarization replaced the intrinsic bursts by a sustained repetitive discharge of single APs and caused intrinsic bursts to appear during previously subthreshold depolarizing current pulses. These NE-increased activities were abolished by dihydropyridine nitrendipine (1 microM) and by Cd2+ (0.5 mM) or Co2+ (2 mM), thus confirming that Ca2+ currents contribute to burst generation in IB cells. 4. In both NB and SB cells recorded in slices from GWS rats, NE provoked the appearance of intrinsic bursts of APs during steps of depolarizing current injections. In addition, in NB cells, NE caused synaptic bursts to appear after white matter stimulation. These NE-induced bursts were dihydropyridine (nitrendipine, 1 microM)- and Cd2+ (0.5 mM)- or Co2+ (2 mM)-sensitive and were related to an increased AP-afterdepolarization. The fast AP-afterhyperpolarization was not affected by NE. In NB cells recorded in slices from saline-infused rats (n = 4) NE did not provoke the appearance of bursts even when stimulation intensity was increased up to three times.(ABSTRACT TRUNCATED AT 400 WORDS)

Subdermal contraceptive implants in nurse-midwifery practice.

Subdermal contraceptive implants have only recently been approved for use in the United States. At present, only one subdermal contraceptive implant, Norplant, is approved in the United States. This article describes the development of Norplant, its efficacy and safety, a description of the system, education for clients, side effects, indications and contraindications, insertion and removal, incorporation into midwifery practice, and education for health professionals regarding its use.

PIP: The US Food and Drug Administration approved the contraceptive implant system, Norplant, in February 1990. It has been used in other countries for more than 15 years before the US approved it. The 6 subdermally placed capsules in the upper inner arm release 50-80 mcg levonorgestrel/day into the bloodstream, resulting in a 99.8% efficacy rate. Patient education and counseling, especially about changes in the bleeding pattern and Norplant's inability to protect against sexually transmitted diseases, are important to maintain client satisfaction and continued use of Norplant. Side effects, from most to least common, are changes in menstrual bleeding, constant bleeding, missed periods, weight gain/increased appetite, headache, oily skin or acne, weight loss/nausea, breast tenderness, nervousness or loss of appetite, and hair loss. It is rare when complications are so severe that they require removal of the implants. Contraindications to Norplant include active liver disease, active thromboembolic disease, breast cancer, pregnancy, and undiagnosed dysfunctional uterine bleeding. Antiepileptic medications, barbiturates, treatment for tuberculosis, and Butazolidin/phenylbutazone reduce Norplant's efficacy. A trained person should insert Norplant within the first 5-7 days of the menstrual cycle when it is evident there is no pregnancy. Some reports recommend that, after childbirth, it should be inserted 6 weeks postpartum to avoid hemorrhage. Yet, nurse-midwives at the Center for Addiction and Pregnancy at the Francis Scott Key Medical Center in Baltimore, Maryland, insert Norplant 24-48 hours postpartum in non-breast-feeding mothers with no increase in hemorrhage. Norplant must be removed no longer than 5 years after insertion. Certified nurse-midwives wanting to incorporate Norplant into their practices should follow the Guidelines for the Incorporation of New Procedures into Nurse-Midwifery Practice and have available a consulting physician who is familiar with and skilled in inserting Norplant. The manufacturer conducts training sessions for health professionals.

Extracellular unit responses in the pulvinar-lateral posterior complex of the cat through electrical stimulation of substantia nigra reticulata and lateralis.

Extracellular single-unit responses of neurons in the ipsilateral pulvinar-lateral posterior complex were recorded in 10 encéphale isolé cats with stimulating electrodes implanted in the substantia nigra pars reticulata and pars lateralis. Fifteen percent of 101 pulvinar-lateral posterior complex thalamic neurons increased their spike discharges when the substantia nigra was stimulated and none decreased its activity. The excitatory effect of this stimulation is discussed in relation to the eventual excitatory or inhibitory character of the efferent projection from the substantia nigra pars reticulata and lateralis to the pulvinar-lateral posterior complex.

Evidence for a nigro-pulvinar-lateralis posterior complex projection in the cat using horseradish peroxidase neuronal retrograde technique.

The possible existence of a direct projection from the substantia nigra to the pulvinar-lateral posterior complex (Pul-LP) was investigated in the cat by using the horseradish peroxidase technique. In particular horseradish peroxidase was injected in the Pul-LP of 8 animals, either unilaterally or bilaterally. Tissue sections obtained from the cat's brain 24-48 hrs. after injection were prepared according to Mesulam's method as slightly modified by the authors. Retrogradelly labelled neurons were observed in substantia nigra pars lateralis and reliculata ipsilaterally to the injected pulvinar-lateral posterior complex. A small number of labelled cells were also found in the contralateral substantia nigra. These findings demonstrate the existence of a close connection between two system which are involved in turning behavior: the nigrostriatal and the pulvinar-lateral posterior complex-superior colliculus.