Use of High-Dose Hydroxocobalamin for Septic Shock: A Case Report

In this case report, we describe 2 patients with septic shock requiring high-dose vasopressors for hemodynamic support despite aggressive fluid resuscitation. After the administration of high-dose hydroxocobalamin for presumed septic vasoplegic syndrome, both patients had an immediate response to hydroxocobalamin with a rapid and lasting improvement of blood pressure that significantly reduced the need for vasopressor support.

Effects of phenylephrine on cardiac output and venous return depend on the position of the heart on the Frank-Starling relationship

Introduction: phenylephrine is used daily during anesthesia for treating hypotension. However, the effects of phenylephrine on cardiac output (CO) are not clear. We hypothesized that the impact of phenylephrine on cardiac output is related to preload dependency. Methods: eight pigs were studied at a preload independent stage (after CO augmentation) and at a preload dependent stage (after a 21 ml/kg hemorrhage). At each stage, phenylephrine boluses (0.5, 1.0, 2.0, and 4.0 μg/kg) were given randomly while mean arterial pressure (MAP), CO, inferior vena cava flow (IVCf) (both measured using ultrasonic flow probes), and pulse pressure variation were measured. Results: at the preload independent stage, phenylephrine boluses induced significant increases in MAP (from 72 ± 6 to 100 ± 6 mmHg; P < 0.05) and decreases in CO and IVCf (from 7.0 ± 0.8 to 6.0 ± 1.1 l/min and from 4.6 ± 0.5 to 3.8 ± 0.6 l/min, respectively). At the preload-dependent stage, phenylephrine boluses induced significant increases in MAP (from 40 ± 7 to 65 ± 9 mmHg), CO (from 4.1 ± 0.6 to 4.9 ± 0.7 l/min), and IVCf (from 3.0 ± 0.4 to 3.5 ± 0.6 l/min; all data presented are for 4 μg/kg). Incremental doses of phenylephrine induced incremental changes in cardiac output. A pulse pressure variation >16.4% before phenylephrine predicted an increase in stroke volume with a 93% sensitivity and a 100% specificity. Conclusion: impact of phenylephrine on cardiac output is related to preload dependency. When the heart is preload independent, phenylephrine boluses induce on average a decrease in cardiac output. When the heart is preload dependent, phenylephrine boluses induce on average an increase in cardiac output.

OSP/claudin-11 forms a complex with a novel member of the tetraspanin super family and beta1 integrin and regulates proliferation and migration of oligodendrocytes

Oligodendrocyte-specific protein (OSP)/claudin-11 is a major component of central nervous system myelin and forms tight junctions (TJs) within myelin sheaths. TJs are essential for forming a paracellular barrier and have been implicated in the regulation of growth and differentiation via signal transduction pathways. We have identified an OSP/claudin-11-associated protein (OAP)1, using a yeast two-hybrid screen. OAP-1 is a novel member of the tetraspanin superfamily, and it is widely expressed in several cell types, including oligodendrocytes. OAP-1, OSP/claudin-11, and beta1 integrin form a complex as indicated by coimmunoprecipitation and confocal immunocytochemistry. Overexpression of OSP/claudin-11 or OAP-1 induced proliferation in an oligodendrocyte cell line. Anti-OAP-1, anti-OSP/claudin-11, and anti-beta1 integrin antibodies inhibited migration of primary oligodendrocytes, and migration was impaired in OSP/claudin-11-deficient primary oligodendrocytes. These data suggest a role for OSP/claudin-11, OAP-1, and beta1 integrin complex in regulating proliferation and migration of oligodendrocytes, a process essential for normal myelination and repair.

Cross-sectional study of sexual behaviour and knowledge about HIV among urban, rural, and minority residents in Viet Nam

OBJECTIVE

A cross-sectional survey was conducted in three districts of Quang Ninh province, Viet Nam, to find out what proportion of the people who lived there engaged in behaviour that put them at risk of becoming infected with HIV, and to measure their knowledge about HIV infection and AIDS.

METHODS

The survey was conducted in a rural district, Yen Hung; a mountainous district inhabited primarily by ethnic minority groups, Binh Lieu; and an urban district, Ha Long. Participants aged 15-45 years were randomly selected from the general population to be interviewed.

FINDINGS

A total of 630 people from 707 households were interviewed; 8% were not home despite repeated visits and 3% refused to participate. The prevalence of premarital intercourse ranged from 9% to 16% among married men and 4% to 7% among married women. Among single men the proportion who had ever had intercourse ranged from 6% to 16%. Fewer than 3% reported having ever had sex with a sex worker. The median number of extramarital sex partners was 1. Knowledge about HIV/AIDS was high in the urban and rural areas but low in the mountainous area. Being male and being 20-29 years old were associated with having multiple sex partners.

CONCLUSION

The low prevalence of individuals reporting that they had had intercourse with sex workers and partners other than their spouse may explain the low rates of HIV infection among the heterosexual population; these rates are in contrast to the high rates of HIV infection found among injecting drug users. The association between having extramarital partners and being a younger man suggests that the tendency to have more sexual partners may increase in the future. If this happens, the potential for HIV to be spread through heterosexual sex will increase.

Estrogen supplementation in the posthypoxic myoclonus rat model

The objective of the study was to investigate the effects of estrogen on severity and duration of myoclonus in the rat cardiac arrest model of posthypoxic myoclonus. Female sex hormones affect a variety of movement disorders and alter dopaminergic and serotonergic pharmacology. Although women represented three-fourths of patients from the original report of Lance and Adams and 80% of the largest published series, the impact of estrogens on myoclonus has never been studied. Twelve previously ovariectomized female rats underwent 8 minutes of mechanically induced cardiac arrest and were resuscitated according to a standardized protocol. On the same day, they were randomly assigned to subcutaneous treatment with a 21-day, 0.5-mg, 17 beta-estradiol or matching placebo pellet. Animals were tested daily with 7 sets of 45 auditory stimuli for 10 days, and myoclonus scores were obtained using a 5-point interval scale. Comparisons were based on two-sample Wilcoxon rank-sum tests. Estrogen treatment significantly enhanced myoclonus intensity and duration: mean peak myoclonus score, 210.2 +/- 18.0 versus 180 +/- 28.5 (p = 0.031); mean number of days above baseline, 9.2 +/- 0.4 versus 5.7 +/- 2.3 (p = 0.004); mean score on day 10, 90.7 +/- 38.7 versus 27.0 +/- 20.6 (p = 0.016). All estrogen-treated animals were above baseline on day 10 compared with none in the placebo group. Estrogen enhances and prolongs posthypoxic myoclonus, suggesting that female gender and estrogen status may play a pivotal role as a risk factor for human posthypoxic myoclonus.

Pramipexole attenuates the dopaminergic cell loss induced by intraventricular 6-hydroxydopamine

The D3 preferring dopamine agonist pramipexole has been shown to attenuate the cell loss induced by levodopa in vitro. Pramipexole was herein evaluated in the 6-hydroxydopamine lesion model to determine its in vivo effect. Rats were treated with pramipexole or saline before and after an intracerebroventricular 6-hydroxydopamine injection. In the preliminary study, 6-hydroxydopamine produced a 68% reduction in striatal dopamine and a 62% loss in tyrosine hydroxylase immunoreactive (THir) cell counts in the substantia nigra. Pramipexole treated animals exhibited a 29% and a 27% reduction in striatal dopamine and THir cell counts, respectively. THir cell counts and striatal dopamine were significantly correlated. In the stereological study, 6-hydroxydopamine reduced THir cell counts by 47% in saline treated animals and 26% in pramipexole treated animals. These data demonstrate that pramipexole attenuates the biochemical and THir cell changes normally produced by 6-hydroxydopamine consistent with its neuroprotective actions in vitro.

Striatal trophic activity is reduced in the aged rat brain

Our previous studies demonstrated that the survival of a mesencephalic graft was reduced in aged animals suggesting an age-related decline in target-derived neurotrophic activity. We tested this hypothesis by examining dopamine (DA) and trophic activities from the striatum of intact or unilateral 6-hydroxydopamine (6-OHDA) lesioned rats of increasing age. Fisher 344 rats were 4, 12, 18, and 23 months old (m.o.) at sacrifice. Half the animals had received unilateral 6-OHDA lesions of the mesostriatal DA pathway 8 weeks earlier. Striatal tissue punches were analyzed for DA, homovanillic acid (HVA), and DA activity (HVA/DA) using HPLC. The remainder of the striatal tissue was homogenized to generate tissue extracts which were added to E14.5 ventral mesencephalic cultures to test trophic activity. In the non-lesioned animals, striatal DA was reduced and striatal DA activity was increased in the 18 and 23 m.o. animals relative to the 4 and 12 m.o. animals. Striatal trophic activity was inversely related to age. In the lesioned animals, striatal DA ipsilateral to 6-OHDA infusion was below detection limits while the contralateral striatum exhibited age-related changes in DA similar to those seen in the non-lesioned animals. In 4 m.o. lesioned rats, striatal trophic activity ipsilateral to 6-OHDA infusion was elevated by 26% relative to the contralateral side. The ipsi/contra-lateral differences in striatal trophic activity were reduced in 12 m.o. animals and absent in the 18 and 23 m.o. groups. These data suggest that advancing age is associated with a reduction in striatal DA as well as trophic activity. Moreover, the aged striatum loses its ability to biochemically and trophically compensate for DA reduction and therefore may represent a more challenging environment for the survival, growth, and function of a fetal graft.

Localization and developmental expression patterns of the neuronal K-Cl cotransporter (KCC2) in the rat retina

The processing of signals by integrative neurons in the retina and CNS relies strongly on inhibitory synaptic inputs, principally from GABAergic and glycinergic neurons that serve primarily to hyperpolarize postsynaptic neurons. Recent evidence indicates that the neuron-specific K-Cl cotransporter 2 (KCC2) is the major chloride extrusion system permitting hyperpolarizing inhibitory responses. It has been hypothesized that depolarizing GABA responses observed in immature neurons are converted to hyperpolarizing responses in large part by the expression of KCC2 during the second week of postnatal development. The cell-specific localization and developmental expression of KCC2 protein have been examined in relatively few neural tissues and have never been studied in retina, of which much is known physiologically and morphologically about inhibitory synaptic circuits. We examined the localization of KCC2 in adult rat retina with immunohistochemical techniques and determined the time course of its postnatal expression. KCC2 expression was localized in horizontal cells, bipolar cells, amacrine cells, and, most likely, ganglion cells, all of which are known to express GABA receptor subtypes. Developmentally, KCC2 expression in the retina increased gradually from postnatal day 1 (P1) until P14 in the inner retina, whereas expression was delayed in the outer plexiform layer until P7 but reached its adult level by P14. These data support the hypothesis that the function of KCC2 is intimately involved in GABAergic synaptic processing. Furthermore, the delayed temporal expression of KCC2 in the outer plexiform layer indicates that GABAergic function may be differentially regulated in retina during postnatal development and that GABA may produce depolarizing responses in the outer plexiform layer at times when it generates hyperpolarizing responses in the inner plexiform layer.

Prenatal cocaine exposure reduces glial cell line-derived neurotrophic factor (GDNF) in the striatum and the carotid body of the rat: implications for DA neurodevelopment

Glial cell line-derived neurotrophic factor (GDNF) is a glycosylated, disulfide-bonded homodimer, and a member of the transforming growth factor-beta superfamily. GDNF has been shown to promote the survival and morphological differentiation of dopamine (DA) neurons and increase their high-affinity dopamine uptake. In order to determine whether the mechanism for our previously observed cocaine-induced DA reductions in brain and carotid body were GDNF-mediated, we exposed Sprague-Dawley rat fetuses to cocaine via maternal subcutaneous injections (30 mg/kg b.i.d., E7-E19). Brains and carotid bodies of fetuses were excised and processed for assessment of GDNF levels using an Enzyme-Linked ImmunoadSorbent Assay (ELISA). ANOVA indicated that cocaine reduced carotid body GDNF by 36% (F((1,5))=28. 11, p<0.05) and striatal GDNF by 41% (F((1,5))=41.77, p<0.01). Although there was no interaction between drug exposure and fetal uterine position, post-hoc pairwise comparisons indicated that reductions in GDNF in the cocaine groups were due to differences at more distal positions (positions 4-8). The magnitude of the reductions in striatal GDNF (but not carotid body GDNF) in both cocaine-exposed and control fetuses followed a cervical (smallest GDNF reductions) to ovarian (greatest GDNF reductions) uterine position gradient. This pattern was similar to that which we observed in prior studies examining DA reductions in brain following prenatal cocaine exposure. The finding that cocaine reduces GDNF levels in striatum and carotid body support the hypothesis that cocaine's ability to reduce striatal and carotid body DA may be indirect through its ability to reduce GDNF. These data along with previous findings support the hypothesis that cocaine's effects on DA neurons are at least partially due to its indirect effects on trophic activity. The possible mechanisms whereby cocaine affects trophic activity are discussed.

Animal model of posthypoxic myoclonus: effects of serotonergic antagonists

OBJECTIVE

To study specific serotonin (5-hydroxytryptamine [5-HT]) receptor subtype antagonists in an animal model of posthypoxic myoclonus.

BACKGROUND

Although serotonergic system dysfunction is implicated in posthypoxic myoclonus, anatomic specificity and linkage to receptor subtypes are not delineated.

METHODS

The authors performed a pharmacologic study to identify specific serotonin receptor subtype antagonists effective in inhibiting myoclonus in posthypoxic rats. Sprague-Dawley rats underwent cardiac arrest for 8 minutes and were resuscitated. On the day of pharmacologic testing, animals were rated every 10 minutes at -30 minutes to time 0 (drug injection) and from +60 to +150 minutes. Using a blinded methodology, animals were injected with normal saline, vehicle, or one of seven serotonin antagonists given at a dose that maintains serotonin receptor subtype specificity: WAY100135 (5-HT1A), methiothepin mesylate (5-HT1B/1D/2), mesulergine hydrochloride (5-HT2A/2B), GR 127935 (5-HT1D), SR 46349 (5-HT2), ondansetron (5-HT3), or GR 125487 (5-HT4). Drugs that produced a significant decrease in myoclonus compared with the control were studied in a dose-response study with six doses across a range from the original dose studied to 10% of that dose.

RESULTS

Two drugs were significantly different from placebo: methiothepin mesylate and mesulergine hydrochloride. GR 127935 showed a trend toward reducing myoclonus. Dose-response studies showed that all doses of methiothepin mesylate and the three highest doses of mesulergine hydrochloride inhibited myoclonus effectively.

CONCLUSIONS

5-HT1B, 5-HT2A/2B, and possibly 5-HT1D receptor subtypes likely play a role in posthypoxic myoclonus. More specific 5-HT antagonists that affect these receptor subtypes are candidates for future testing in this model and in Lance-Adams syndrome.

Linear transduction of natural stimuli by dark-adapted and light-adapted rods of the salamander, Ambystoma tigrinum

1. We examined signal, noise and response properties of salamander rod photoreceptors by measuring: (a) the circulating current of rods which were adapted to darkness and to a wide range of backgrounds; (b) contrasts of natural environments; (c) the effect of adaptation on the linear response range of rods; and (d) the behaviour of rods responding to dynamically modulated stimuli having a range of contrasts found in nature. 2. In the dark, the circulating current contained two noise components analogous to those described in toad. A discrete noise component consisted of events occurring at a rate of 1 event per 32 s (21 degrees C) and had a variance of 0.036 pA2. A continuous noise component contributed 0.022 pA2 to the dark current, roughly equal to the discrete noise variance. 3. Exposure to a wide range of steady backgrounds (suppressing up to 80% of the circulating current), elicited a sustained fluctuating photocurrent having a power spectrum which resembled those of single photon responses and was consistent with the linear summation of single photon events; this indicates that the primary source of noise in the current is caused by the light. 4. Eighty-nine per cent of the contrasts (C) measured in natural environments had magnitude of C < 50%, where C = magnitude of I - Imean/magnitude of Imean. The linear response range elicited by brief flashes expanded with brighter backgrounds, well-encompassing flash contrasts of 100%. 5. Dynamically modulated stimuli and incremental flashes having contrasts similar to those in natural scenes elicited small currents which deviated by a few picoamps about the mean and the transfer functions computed from each type of stimulus-response pair closely corresponded to one another. These results indicate that in natural environments, rods behave as linear small-signal transducers of light.

Neuroprotective effects of the strychnine-insensitive glycine site NMDA antagonist (R)-HA-966 in an experimental model of Parkinson's disease

The neuroprotective effects of (R)-HA-966 and (S)-HA-966 (3-amino-1-hydroxy-2-pyrrolidinone) were examined in an MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced animal model of Parkinson's disease. Systemic pretreatment of C57 black mice with the strychnine-insensitive glycine site antagonist, (R)-HA-966 (3-30 mg/kg, i.p.), dose-dependently attenuated MPTP-induced depletion of striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC). Pretreatment with (R)-HA-966 also significantly protected the degeneration of tyrosine hydroxylase-positive neurons in the substantia nigra of mice treated with MPTP and alleviated the acute behavioral changes caused by the neurotoxin. In contrast, the other racemic form, (S)-HA-966, neither prevented the neurochemical depletions nor the neuronal injury caused by MPTP. These results indicate that excitatory mechanisms of neurodegeneration are involved in the pathophysiology of Parkinson's disease, and that strychnine-insensitive glycine site NMDA antagonists may serve as dopaminoprotective agents which intervene in the progressive neurodegeneration in Parkinson's disease.

The p16 and p18 tumor suppressor genes in neuroblastoma: implications for drug resistance

The cyclin dependent kinase inhibitors p16 and p18 were investigated in neuroblastoma. Only one of 19 neuroblastoma cell lines, an adriamycin-resistant variant, and none of 5 primary neuroblastoma, was deleted for p16 while its parental drug sensitive cell line is p16 intact. The region of deletion minimally extended centromeric to include p15, and telomeric to interferon-beta. This is the first report of a p16 gene alteration in neuroblastoma. No p16 gene hypermethylation or mutations were found. No homozygous deletions of p18 in these samples were found, although several instances of loss of heterozygosity are suspected. No p18 point mutations were detected. We conclude that (1) neither p16 nor p18 are likely involved in the pathogenesis of neuroblastoma; and (2) the role of p16, or another 9p21 gene, in the development of drug resistance warrants further investigation.

Antimyoclonic effect of gabapentin in a posthypoxic animal model of myoclonus

The antimyoclonic property of the novel antiepileptic drug, gabapentin (1-(aminomethyl) cyclohexane acetic acid), was tested in cardiac arrest-and p,p'-DDT(1,1,1-trichloro-2,2-bis (p-chlorophenyl)ethane)-induced animal models of myoclonus. Gabapentin dose-dependently attenuated myoclonus in posthypoxic rats for more than 3 h. The drug was also found to be effective in controlling the early stages of seizures following the anoxic insult. In contrast, the drug was ineffective in controlling either myoclonus or seizures in p,p'-DDT-treated animals. These results suggest that gabapentin can be used used as an effective therapeutic agent in an acute hypoxia/ischemia-induced neurological disorder. The data further indicate that distinct neurological mechanisms may be operating in the expression of myoclonus among posthypoxic and p,p'-DDT-induced animal models.

Integration of a curved hybrid waveguide lens and photodetector array in a GaAs waveguide

For the first time, we believe, the integration of a waveguide lens and a photodetector array in GaAs for operation at a 1.3-microm wavelength is reported. The waveguide lens is a newly devised curved hybrid Fresnel/Bragg chirp grating lens fabricated by the ion-million technique. Desirable performance characteristics, including high throughput efficiency, freedom from coma (up to +/-4 deg off axis), and a near-diffraction-limited focal-spot size, have been demonstrated with this curved hybrid lens. The 10-element photodetector array of the InGaAs photoconducting type shows a measured gain-bandwidth product that is higher than 1 GHz at high frequency, while at a lower frequency the gain is in the range of several thousands. The curved-hybrid-lens-photodetector array combination realized in the GaAs 5 x 13 mm(2) in size has produced a well-resolved element spacing of 10 microm with cross talk that is lower than -14 dB. This lens-photodetector array combination constitutes a basc structure for the realization of monolit ic acousto-optic and electro-optic circuits such as integrated-optic rf spectrum analyzers and multiport switches.

Perineural leads and burst stimulation optimize contraction of skeletal muscle

Electrode position and stimulation mode were hypothesized to be independent variables for the contractile response of skeletal muscle. Perineural and intramuscular electrodes were tested with single and burst pulse generators. Voltage requirements and muscle force generation were measured. Perineural leads improved the efficiency of stimulation for muscle contraction and yielded reduced threshold and plateau voltages compared to intramuscular leads. There were no differences between the different types of perineural leads. Burst stimulation had a wider range of voltage for muscle fiber recruitment and was confirmed to elicit greater maximal force than single stimulation.

Formation of negative-index-change waveguide lenses in LiNbO(3) by using ion milling

We report, for the first time to our knowledge, fabrication of two types of negative-index-change waveguide lens in LiNbO(3) by using ion milling. The first type is an analog Fresnel lens formed by grooves milled into the waveguide. The second is a hybrid lens that combines analog Fresnel zones in the central region with chirp gratings on the sides formed by the same means. We have obtained simultaneously high-efficiency and near-diffraction-limited focusing characteristics in both types of lens. The ion-milling technique employed should be capable of producing similar lenses in any other waveguide substrate, such as GaAs.