Transcranial doppler ultrasonography for the evaluation of shunt malfunction in pediatric patients

Previous studies have demonstrated a high correlation between hydrocephalus and the resistive index (RI), as determined by transcranial Doppler ultrasonography. Measurements of RI, calculated by dividing the difference between the peak systolic velocity and the enddiastolic velocity by the peak systolic velocity, were attempted in 55 pediatric patients during evaluations for ventriculoperitoneal shunt malfunctions; values were obtained in 52. Indications of shunt malfunction included both clinical and radiographic evidence of increased intracranial pressure. Eleven patients, determined to have functional shunts both by clincal criteria and subsequent outcome, had RIs of 47±5 (average±1 standard deviation). Shunt malfunctions were confirmed in 41 patients. Prior to shunt revisions, these 41 patients has RIs of 71±10%; following revision, the RIs fell to 53±12%. Nine patients had had pre-malfunction RIs of 48±11% obtained during routine follow-ups; when they subsequently had shunt malfunctions, their RIs had significantly increased. Four of the 41 patients with shunt malfunctions had essentially normal RIs (52±7%), but had fluid tracking along the shunt; in these, RIs were essentially unaffected by shunt revision. For comparison, 119 pediatric patients with clinically functional ventriculoperitoneal shunts had RIs of 50±9%. The data, statistically significant with a P value of <0.001, showed a correlation between elevated RIs and shunt malfunction; thus, transcranial Doppler ultrasonography is a practical, non-invasive technique useful in the diagnosis of ventriculoperitoneal shunt malfunction.Presented at the Annual Meeting of the Pediatric Section of the American Association of Neurological Surgeons, Washington D.C., November 1989     

Electrotonic coupling among neuroendocrine cells in Aplysia.

1. We have discovered and characterized direct electrotonic synaptic coupling among a population of neuroendocrine (bag) cells in the parietovisceral ganglion of the marine gastropod Aplysia dactylomela. Pairs of ipsilateral and contralateral bag cells were impaled in vitro with microelectrodes. Current pulses applied through the electrometer amplifier to either cell influenced the other cell via electrotonic connections. 2. The coupling between bag cells was relatively weak when measured at the somata; the mean ratio of postsynaptic/presynaptic response amplitudes is 0.0075. Junctional rectification was not detected. The latency between pre- and postjunctional responses was long, up to 50 ms, a delay comparable to that for chemical synaptic transmission among neurons in this ganglion. Low-Ca2+/high-Mg2+ bathing solutions did not block transmission between bag cells, but did block chemical synaptic potentials in other identified neurons. 3. Postjunctional electrotonic responses had markedly slow time courses compared to the prejunctional responses, a characteristic that permitted summation of otherwise undetectable electrotonic PSPs and the demonstration of coupling between the two (bilateral) clusters of bag cells. 4. Based on extracellular recordings of their compound action potentials, the neurites of A. dactylomela bag cells extended a shorter distance (approximately 3 mm) along the connective than the neurites of A. californica or A. brasiliana. 5. Electrolytic lesions made along the neurites during intrasomatic coupling measurements significantly shortened the duration of postjuctional electrotonic responses, indicating that the neurites are widely electrically interconnected and, as a population, have a large effective membrane capacitance. The lesions furthermore revealed that an important site of electrotonic coupling is at the base of the pleurovisceral connective just rostral to the bag cell cluster. 6. The small-amplitude, long-latency and prolonged time course of postjunctional responses are interpreted to indicate remote and widespread coupling sites among the bag cells. This electrotonic coupling underlies the synchronized firing of the bag cells.     

The National Cancer Data Base and physician network

The National Cancer Data Base (NCDB) is a nationwide outcomes database for oncology presently including 1,600 hospitals in 50 states. Half of all U.S. cancer cases are accessioned annually. It is important for U.S. clinicians and health information management professionals to become familiar with the NCDB to increase the usefulness of this comparative database in their hospital quality assurance programs. The NCDB's unique characteristics include its implementation by clinicians, its provision of access to data from hospitals participating in the Approvals Program of the Commission on Cancer, and its affiliation with a 2,200-member national physician network. The NCDB annual data are augmented by patient care evaluation studies, which provide a capability for cross-sectional surveys with an expanded data set. The NCDB has participated in the significant data standardization effort for U.S. cancer registries. The procedures used maintain confidentiality of the patient, physician, and participating hospital, and physical access to the data files is limited. The three primary products of the NCDB are hospital comparative reports, state and local reports, and scientific reports.     

Niche adaptation and genome expansion in the chlorophyll d-producing cyanobacterium Acaryochloris marina

Acaryochloris marina is a unique cyanobacterium that is able to produce chlorophyll d as its primary photosynthetic pigment and thus efficiently use far-red light for photosynthesis. Acaryochloris species have been isolated from marine environments in association with other oxygenic phototrophs, which may have driven the niche-filling introduction of chlorophyll d. To investigate these unique adaptations, we have sequenced the complete genome of A. marina. The DNA content of A. marina is composed of 8.3 million base pairs, which is among the largest bacterial genomes sequenced thus far. This large array of genomic data is distributed into nine single-copy plasmids that code for >25% of the putative ORFs. Heavy duplication of genes related to DNA repair and recombination (primarily recA) and transposable elements could account for genetic mobility and genome expansion. We discuss points of interest for the biosynthesis of the unusual pigments chlorophyll d and α-carotene and genes responsible for previously studied phycobilin aggregates. Our analysis also reveals that A. marina carries a unique complement of genes for these phycobiliproteins in relation to those coding for antenna proteins related to those in Prochlorococcus species. The global replacement of major photosynthetic pigments appears to have incurred only minimal specializations in reaction center proteins to accommodate these alternate pigments. These features clearly show that the genus Acaryochloris is a fitting candidate for understanding genome expansion, gene acquisition, ecological adaptation, and photosystem modification in the cyanobacteria.     

Speech perception in children with cochlear implants for continua varying in formant transition duration

Purpose: To examine the developmental course of labial and alveolar manner of articulation contrasts, and to determine how that course may be different for typically developing (TD) children with cochlear implants (CI).

Method: Eight young adults, eight TD 5–8 year-old children, and seven 5–8 year-old children with CIs participated. Labial /ba/–/wa/ and alveolar /da/–/ja/ continua stimuli were presented, with each continuum consisting of nine synthetic stimuli varying in F2 and F3 transition duration. Participants were asked to label the stimuli as either a stop or glide, and responses were analysed for phonetic boundaries and slopes.

Result: For the /ba/–/wa/ contrast, children with CIs required longer transition durations compared to TD children or adults to cross from one phoneme category to another. The children with CIs demonstrated less confidence in labelling the stimuli (i.e. less steep slopes) than the TD children or the adults. For the /da/–/ja/ contrast, the children with CIs showed less steep slope values than adults.

Conclusion: These results suggest that there are differences in the way TD children and children with CIs develop and maintain phonetic categories, perhaps differences in phonetic representation or in linking acoustic and phonetic representations.