Contribution of BK Ca2+-activated K+ channels to auditory neurotransmission in the Guinea pig cochlea

Large-conductance calcium-activated potassium (BK) channels are known to play a prominent role in the hair cell function of lower vertebrates where these channels determine electrical tuning and regulation of neurotransmitter release. Very little is known, by contrast, about the role of BK channels in the mammalian cochlea. In the current study, we perfused specific toxins in the guinea pig cochlea to characterize the role of BK channels in cochlear neurotransmission. Intracochlear perfusion of charybdotoxin (ChTX) or iberiotoxin (IbTX) reversibly reduced the compound action potential (CAP) of the auditory nerve within minutes. The cochlear microphonics (CM at f1 = 8 kHz and f2 = 9.68 kHz) and their distortion product (DPCM at 2f1-f2) were essentially not affected, suggesting that the BK specific toxins do not alter the active cochlear amplification at the outer hair cells (OHCs). We also tested the effects of these toxins on the whole cell voltage-dependent membrane current of isolated guinea pig inner hair cells (IHCs). ChTX and IbTX reversibly reduced a fast outward current (activating above -40 mV, peaking at 0 mV with a mean activation time constant tau ranging between 0.5 and 1 ms). A similar block of a fast outward current was also observed with the extracellular application of barium ions, which we believe permeate through Ca2+ channels and block BK channels. In situ hybridization of Slo antisense riboprobes and immunocytochemistry demonstrated a strong expression of BK channels in IHCs and spiral ganglion and to a lesser extent in OHCs. Overall, our results clearly revealed the importance of BK channels in mammalian cochlear neurotransmission and demonstrated that at the presynaptic level, fast BK channels are a significant component of the repolarizing current of IHCs.     

Transmission of hepatitis B virus from mother to child in Bamako-Mali]

Results of a study about mother-infant transmission of hepatitis B virus (HBV) confirm the high degree of positivity of HBV markers in Bamako, Republic of Mali. Among 372 sera of mother-newborn pairs, seroprevalence of HBs Ag has been around 11% in mothers. The lack of anti HBc IgM in all sera agree probably with a relative old contamination. Pre-S2 epitope marker has been found in more than 70% of HBs Ag positive mothers and 50% of their children. Large discordance has been noted between the prevalence rate of this marker and the HBe Ag and viral DNA, other markers of HBV replication. Further studies are necessary for the clear understanding of HBV transmission systems in our country.     

Analysis of human erythrocyte 5'-nucleotidases in healthy individuals and a patient deficient in pyrimidine 5'-nucleotidase

Electrophoretic and quantitative analysis of pyrimidine 5'-nucleotidase in human erythrocytes from healthy individuals and a patient deficient in pyrimidine 5'-nucleotidase, using a range of substrates, has shown that the patient has a marked deficiency with UMP, CMP and dCMP as substrates but near normal levels of activity with dUMP and dTMP as substrates. The observations suggest that two separate structural gene loci coding for distinct 5'-nucleotidases with similar electrophoretic mobility exist in man. The genetic determination of these enzymes seems therefore to be homologous with that found in rodents.     

Optimal control problems with Atangana‐Baleanu fractional derivative

In this paper, we study fractional‐order optimal control problems (FOCPs) involving the Atangana‐Baleanu fractional derivative. A computational method based on B‐spline polynomials and their operational matrix of Atangana‐Baleanu fractional integration is proposed for the numerical solution of this class of problems. With this numerical technique, the FOCPs are reduced to a system of equations which are solved for the unknown parameters with the help of Mathematica® software. Our results show the applicability and usefulness of the numerical technique.     

Differential effects of zidovudine and zidovudine triphosphate on mitochondrial permeability transition and oxidative phosphorylation

1. The effects of zidovudine (ZDV) and zidovudine triphosphate (ZDV-3P) on Ca²⁺-induced mitochondrial permeability transition (MPT), respiratory control ratio (RCR) and ATP synthesis have been investigated on isolated rat liver mitochondria.
2. ZDV slightly but significantly decreased RCR and ATP synthesis but was ineffective in inhibiting MPT. In contrast, ZDV-3P did not alter RCR and ATP synthesis but strongly inhibited MPT (IC₅₀=3.0±0.9 μM).
3. The effect of ZDV-3P on mitochondrial swelling required a preincubation time. When incubated 10 min with mitochondria, ZDV-3P (8 μM) totally inhibited the rate of swelling.
4. ADP, ATP and atractyloside, which are agents known to interact with the mitochondrial adenine nucleotide carrier (ANC), antagonized the effect of ZDV-3P on mitochondrial swelling. Indeed, the IC₅₀ value of ZDV-3P increased from 3.0 to 17.4, 93.6 and 66.5 μM, in the presence of 20 μM, ADP, ATP or atractyloside, respectively.
5. ZDV-3P did not displace [³H]-ATP from its mitochondrial binding site(s) whereas ADP and atractyloside did, suggesting that ZDV-3P and [³H]-ATP do not share the same binding sites.
6. ZDV-3P did not affect either mitochondrial respiration or ATP synthesis but inhibited Ca²⁺-dependent mitochondrial swelling. It was concluded that mitochondrial toxic effects observed during the chronic administration of ZDV cannot be related to its active metabolite (ZDV-3P).

     

Three cases of dural arteriovenous fistula of the anterior condylar vein within the hypoglossal canal

Dural arteriovenous fistulas (DAVFs) of the anterior condylar vein are an uncommon but important subset of fistulas occurring at the skull base that can be confused with DAVFs of the marginal sinus on angiography. MR angiography source images can document the intraosseous extent and the relationship to the hypoglossal canal of this type of fistula, which can have significant clinical implications. We present the imaging features of angiography, CT, and MR angiography of three cases of DAVFs localized to the anterior condylar vein and within the hypoglossal canal, which were confirmed by source images from MR angiography. Transvenous coil embolization was curative in two of three cases and would seem to be the treatment of choice when venous access is available.     

Safety of intrauterine device insertion by trained nurse-midwives in the Sudan

Insertion of intrauterine devices (IUDs) by trained health workers other than physicians is increasing, particularly in developing countries. Twenty nurse-midwives in government service in the Sudan, called health visitors (HVs), were trained to provide intrauterine contraceptives in a research project designed to evaluate the safety of insertion of IUDs by medical personnel who are not physicians. After training, they inserted 763 IUDs. Independent evaluation of 520 clients was conducted by gynecologists who found that only six devices (1.2%) had been incorrectly inserted. Outcomes for clients of the health visitors, with respect to perforations, infections, expulsions, and pregnancies, compared well with those of eight physicians who participated in the study. The research strongly supports the concept of nurse-midwife training for IUD insertion. This would greatly expand the availability of family planning services and would conserve physician time and skills for problem cases.     

Screening of some food poisoning bacteria in sausage and hamburger meat

Microbial investigation of 30 samples of sausage meat and 30 samples of hamburger meat, freshly prepared, were collected randomly from different markets in Alexandria city, to determine the bacteriological status of these products. The average counts/gm of total bacteria, total coliforms and fecal coliform in sausage meat were 1.33 x 10(7), 9.16 x 10(5) and 1.11 x 10(3) respectively, and in hamburger samples were 8.47 x 10(5), 2.63 x 10(3) and 1.35 x 10(3) respectively. Shigella, Escherichia coli, Staphylococcus aureus and Proteus spp were isolated with various percentages, whereas Salmonella spp was isolated from sausage only. The public health importance of the isolated microorganisms are fully discussed.     

Volume control during periodic changes of blood volume in the alert rat

Summary Blood (3.4–13.5% of blood volume) was pumped in and out of the circulation of rats at different rates and period lengths during continuous measurements of blood conductivity (reciprocally related to hematocrit) and arterial pressure. Hct followed the same zig-zag course as the induced changes of blood volume in every case, indicating that fluid shifts (v) between interstitium and intravascular space closely follow blood volume changes. As the het increase during reinfusion was not as great as the preceding decrease, hct dropped continuously during the 20–90 minutes of experimentation, so that a final volume increase (v) by about 4% was calculated, which was confirmed by a corresponding decrease of plasma protein concentration. Both final v and v during periodic volume change (% B.V.) were greater when arterial pressure dropped. v was directly related to % B.V. but not to its rate of change. Heart rate dropped slightly at the end of the reinfusion periods, whereas it rose to control at the end of the withdrawal periods. The results were regarded as evidence of blood volume regulation proportional to the absolute volume of blood lost in non-hypotensive hemorrhage.Supported by DFG-grant AZ 3/3