Oocyte maturation in vitro

In contrast to conventional assisted reproduction techniques in which metaphase II oocytes are retrieved for fertilization in vitro, during the in-vitro maturation of oocytes, immature germinal vesicle stage oocytes are retrieved and matured in the laboratory before fertilization and embryo transfer. Whereas in-vitro maturation is technically more demanding than in-vitro fertilization it carries many potential advantages in terms of lower treatment costs and greater safety, as a result of reducing both the number of clinical consultations and the amount of pharmacological intervention. Although the technology is still experimental, in-vitro maturation has been successfully used for the treatment of patients with polycystic ovarian syndrome, and a number of pregnancies and live births have been reported. Despite these successes and much continuing research effort, the overall efficiency of in-vitro maturation remains low, and neither clinical nor laboratory procedures can be considered to be as robust and routinely feasible as conventional in-vitro fertilization techniques. The immediate goals for in-vitro maturation programmes are therefore to increase germinal vesicle oocyte recovery rates, optimize culture conditions, improve oocyte maturation potential, and after fertilization to produce pregnancy rates that are at least equivalent to those obtained using conventional in-vitro fertilization. This review focuses on the physiology and application of human oocyte maturation in vitro, and will detail the recent advances reported in this rapidly advancing field.     

Estimating the audiogram using multiple auditory steady-state responses

Multiple auditory steady-state responses were evoked by eight tonal stimuli (four per ear), with each stimulus simultaneously modulated in both amplitude and frequency. The modulation frequencies varied from 80 to 95 Hz and the carrier frequencies were 500, 1000, 2000, and 4000 Hz. For air conduction, the differences between physiologic thresholds for these mixed-modulation (MM) stimuli and behavioral thresholds for pure tones in 31 adult subjects with a sensorineural hearing impairment and 14 adult subjects with normal hearing were 14+/-11, 5+/-9, 5+/-9, and 9+/-10 dB (correlation coefficients .85, .94, .95, and .95) for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. Similar results were obtained in subjects with simulated conductive hearing losses. Responses to stimuli presented through a forehead bone conductor showed physiologic-behavioral threshold differences of 22+/-8, 14+/-5, 5+/-8, and 5+/-10 dB for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. These responses were attenuated by white noise presented concurrently through the bone conductor.     

Human auditory steady-state responses to tones independently modulated in both frequency and amplitude

OBJECTIVE: Independent amplitude and frequency modulation (IAFM) of a carrier tone uses two different modulating frequencies, one for amplitude modulation (AM) and one for frequency modulation (FM). This study measured the human steady-state responses to multiple IAFM tones. The first question was whether the IAFM responses could be recorded without attenuation of the AM and FM components. The second question was whether IAFM stimuli would provide a more effective demonstration of responses at intensities near threshold than the responses to AM tones. The third question was whether the responses to multiple IAFM stimuli would relate to the discrimination of words at different intensities. DESIGN: Multiple AM, FM, or IAFM stimuli were presented simultaneously. Responses were recorded between the vertex and the neck and analysed in the frequency domain. The first experiment compared IAFM responses with AM and FM responses. The second experiment compared IAFM responses with AM responses between intensities 20 to 50 dB SPL. The third experiment related the IAFM responses to the discrimination of monosyllabic words at intensities between 20 and 70 dB SPL. RESULTS: Steady-state responses to the individual component of the IAFM stimuli were clearly recognizable although attenuated a little (14%) from the responses to AM or FM alone. Using IAFM stimuli was not different than simply using AM stimuli when trying to recognize responses at low intensities. The number of responses detected during multiple IAFM stimulation and the amplitudes of these responses correlated significantly with word discrimination. CONCLUSIONS: IAFM of a carrier using two different modulating frequencies (one for AM and one for FM) elicits separate AM and FM responses that are relatively independent of each other. These separate responses can be used to detect whether a particular carrier has been processed in the cochlea, but they are not as effective as measuring responses to carriers that have been modulated in both amplitude and frequency at the same modulation frequency (mixed modulation). The detectability of eight different responses (four AM and four FM) to an IAFM stimuli relates well to the ability of subjects to discriminate words. IAFM stimuli therefore show promise as an objective test for assessing suprathreshold hearing.     

Possible role of diadenosine polyphosphates in glucose-stimulated insulin release: effects of NaF upon metabolic and functional variables in rat isolated islets

Diadenosine polyphosphates, such as diadenosine triphosphate (A2P3) and diadenosine tetraphosphate (A2P4), were recently proposed to participate in the stimulus-secretion coupling for nutrient-stimulated insulin release. Since NaF, an inhibitor of inorganic pyrophosphatase, was reported to lower A2P3 and A2P4 content in glucose-stimulated pancreatic islets, its effects upon metabolic, cationic, biosynthetic and secretory variables in rat pancreatic islets were investigated in the present study. Up to a concentration close to 0.1 mM, NaF failed to affect most of these variables, except for a decrease in 45Ca net uptake. Much higher concentrations of NaF (e.g. 5.0 mM) were required to cause inhibition of the metabolic, ionic, biosynthetic and secretory responses of the islets to nutrient secretagogues. Yet, even at this high concentration, NaF failed to lower the islet content in tritiated A2P3 and A2P4 in islets prelabelled with [2,8-3H]adenosine and failed to prevent the glucose-induced increase in such a content. It is concluded, therefore, that NaF may not represent a suitable tool to assess the participation of diadenosine polyphosphates in the process of nutrient-induced insulin secretion.     

CD40 upregulation is independent of HHV-8 in the pathogenesis of Kaposi's sarcoma.

AIMS: Human herpesvirus 8 (HHV-8) is now acknowledged as the infective cofactor in the pathogenesis of Kaposi's sarcoma. The mode by which HHV-8 causes Kaposi's sarcoma is unresolved and it is probable that it acts in conjunction with other factors including cytokines, anti-apoptosis proteins, and cell surface receptors. CD40, a cell membrane receptor belonging to the tumour necrosis factor receptor super family, promotes B cell survival and is expressed constitutively on endothelial cells. It is upregulated on cytokine treatment and has been documented recently in Kaposi's sarcoma. Because the HHV-8 genome contains cytokine homologues, this study investigated whether CD40 expression in Kaposi's sarcoma correlated with HHV-8 status, using a unique set of HHV-8 positive and negative specimens. METHODS: Twenty one paraffin wax embedded samples of Kaposi's sarcoma were selected, of which 18 were screened for the presence of HHV-8 using both conventional solution phase and TaqMan polymerase chain reaction (PCR). CD40 immunohistochemistry was assessed using a biotinylated amplification system. Staining was scored semiquantitatively. RESULTS: The results indicated that the expression of CD40 is independent of viral status, being present in both HHV-8 positive and negative specimens. CONCLUSIONS: This suggests that HHV-8 promotes Kaposi's sarcoma cell survival following infection by mechanisms other than those involving CD40.     

Dimensional changes in the periodontal membrane of monkeys (Macaca irus) due to horizontal thrusts applied to the teeth

The displacement of the root and overlying labial bone was recorded from fifteen anterior teeth in four adult monkeys, using transducers of movement incorporating strain gauges. Horizontal thrusts of 500 g were applied manually. Two phases of root movement were seen when the transducers were some distance from the axis of rotation. This axis tended to move as the force increased for some teeth. Bone distortion was less, but usually in the same direction as the movement of the root. The average change in width of the membrane was approximately 20μ with 500 g force.     

Human auditory steady-state response during general anesthesia

The 40-Hz auditory steady-state evoked response (ASSR) is a sinusoidal electrical response of the brain to periodically presented auditory stimuli. It was recorded during anesthesia in 10 elective surgical patients to evaluate its usefulness as a measure of the level of consciousness. The anesthetic agents used were thiopental, fentanyl, and isoflurane with or without nitrous oxide. Recordings were carried out during the period before induction and during induction, surgical anesthesia, emergence, and recovery from anesthesia. The level of consciousness was measured with an auditory stimulus detection task. The electroencephalogram (EEG) was also recorded for comparison with the ASSR. The following indices were analyzed: total EEG power, relative power in the beta, alpha, theta, and delta frequency bands, and the median and spectral edge frequency. The amplitude of the ASSR was reduced significantly at the end of the induction period and decreased below noise levels during surgical anesthesia. It increased significantly during emergence and recovery. The amplitude during recovery remained significantly smaller than the preinduction values. The changes of the ASSR paralleled those of the level of consciousness. The EEG measurements were distorted by the presence of muscle artifacts that were prominent during emergence and recovery. The amplitude of the ASSR appears to provide a more reliable indicator of the level of consciousness than the EEG.