Avian-to-human transmission of H9N2 subtype influenza A viruses: relationship between H9N2 and H5N1 human isolates

In 1997, 18 cases of influenza in Hong Kong (bird flu) caused by a novel H5N1 (chicken) virus resulted in the deaths of six individuals and once again raised the specter of a potentially devastating influenza pandemic. Slaughter of the poultry in the live bird markets removed the source of infection and no further human cases of H5N1 infection have occurred. In March 1999, however, a new pandemic threat appeared when influenza A H9N2 viruses infected two children in Hong Kong. These two virus isolates are similar to an H9N2 virus isolated from a quail in Hong Kong in late 1997. Although differing in their surface hemagglutinin and neuraminidase components, a notable feature of these H9N2 viruses is that the six genes encoding the internal components of the virus are similar to those of the 1997 H5N1 human and avian isolates. This common feature emphasizes the apparent propensity of avian viruses with this genetic complement to infect humans and highlights the potential for the emergence of a novel human pathogen.

Voltage-dependent K(+) currents in spiral prominence epithelial cells of rat cochlea

It has been suggested that spiral prominence is associated with ion transport, but the characterization of ion channels has not been explored so far. We studied the electrical properties and ion conductances of the spiral prominence epithelial cells (SPECs), which are epithelial cells covering the luminal side of spiral prominence, in the upper turn of neonatal rat cochlea using a whole-cell variant patch clamp technique. The cell capacitance was 16.3+/-2.1 pF (n=33) and the resting membrane potential was -68. 9+/-2.5 mV (n=14) in perilymph-like bath solution. It was found that those SPECs possess a large voltage-activated, outwardly rectifying K(+) current and a small inwardly rectifying K(+) current. The outward K(+) current was activated by depolarizing pulses more positive than -30 mV, and sensitive to tetraethylammonium chloride (20 mM), 4-aminopyridine (10 mM), but not to Ba(2+) (0.5 mM). Tail current analysis revealed that it was primarily K(+)-selective. The time course of activation was well fitted by an exponential function raised to second power. The small inwardly rectifying K(+) current was sensitive to Ba(2+) (0.5 mM), and the Ba(2+)-sensitive current was K(+)-selective. In cell-attached or inside-out patch recordings, no discernible K(+) channel currents were found in the apical membrane of SPECs. Based on these results, we conclude that SPECs have two types of voltage-dependent K(+) currents, which are most likely located in the basolateral membrane.

HIV-1 infected women and prenatal care utilization: barriers and facilitators

In an effort to understand issues affecting prenatal care access and utilization from the perspectives of human immunodeficiency virus (HIV)-infected women who receive inadequate prenatal care, we conducted three in-depth qualitative and quantitative interviews. From a thematic analysis of the narrative interviews, four broad areas emerged as pertinent to these women's prenatal care experiences. These were issues related to pregnancy, HIV, psychosocial conditions, and the health care system. For these women, the barriers to prenatal care utilization included the unexpected and unplanned nature of the pregnancy and mental health issues related to HIV infection. Poverty, periodic homelessness, addiction to illicit substances, and lack of social support were also important barriers. Furthermore, perceptions of the health care system as threatening, including fears related to consequences of disclosing illicit activities, discrimination, and breach of confidentiality emerged as salient barriers. Facilitating factors included the pregnancy being experienced as a life-transforming event, concern for their children, especially preventing HIV-1 vertical transmission, availability of treatment, and support from health care professionals. Prominent throughout the interviews were the women's mental health concerns and need for professional support.

Evolutionary characterization of the six internal genes of H5N1 human influenza A virus

The entire nucleotide sequences of all six internal genes of six human H5N1 influenza A viruses isolated in Hong Kong in 1997 were analysed in detail from a phylogenetic point of view and compared with the evolutionary patterns of the haemagglutinin and neuraminidase genes. Despite being isolated within a single year in the same geographical location, human H5N1 viruses were characterized by a variety of amino acid substitutions in the ribonucleoprotein complex [PB2, PB1, PA and nucleoprotein (NP)] as well as the matrix (M) proteins 1 and 2 and nonstructural (NS) proteins 1 and 2. The presence of previously reported amino acid sequences specific for human strains was confirmed in the PB2, PA, NP and M2 proteins. Nucleotide and amino acid sequence identities of the six internal genes of H5N1 viruses examined here were separated into at least two variant groups. In agreement with the above result, phylogenetic trees of the six internal genes of human H5N1 viruses were generally composed of two minor clades. Additionally, variable dendrogram topologies suggested that reassortment among viruses contributed further to the genetic variability of these viruses. As a result, it became clear that human H5N1 viruses are characterized by divergent gene constellations, suggesting the possible occurrence of genetic reassortment between viruses of the two evolutionary lineages.

Inhibition of apamin-sensitive K+ current by hypoxia in adult rat adrenal chromaffin cells

The effect of hypoxia on small-conductance Ca(2+)-activated K+ current was investigated in a study of adult rat adrenomedullary chromaffin cells (AMCs), which were maintained in short-term culture. The nystatin-perforated, whole-cell patchclamp technique was used to study the effect of hypoxia with minimum perturbation of the intracellular milieu. Under voltage-clamp conditions, acute hypoxia (P(O2) approximately equal to 25 mmHg) suppressed the whole-cell outward currents of more than half the AMCs (24/46). This suppression was eliminated after application of apamin (400 nM), a selective inhibitor of small-conductance Ca(2+)-activated K+ current (I(SK)(Ca)) (n=5), suggesting that an apamin-sensitive component of whole-cell currents is suppressed during hypoxia. In contrast to I(SK)(Ca), Ca2+ current (I(Ca)) (n=10) was not affected by hypoxia. Finally, under current-clamp conditions, hypoxia reversibly depolarized the resting membrane potential of adult AMCs (34/40). Apamin, however, eliminated the hypoxia-induced depolarization (400 nM) (7/8), suggesting that hypoxic depolarization is related to the suppression of I(SK(Ca). From the above results, we conclude that adult AMCs are sensitive to hypoxia, and that I(SK)(Ca) contributes to the hypoxia-induced suppression of whole-cell outward current and depolarization of the resting membrane potential in adult AMCs.

Evidence for participation of RNA 1-encoded elicitor in Cowpea mosaic virus-mediated concurrent protection

The cowpea (Vigna unguiculata) line Arlington, inoculated with Cowpea mosaic virus (CPMV), showed no symptoms, and no infectivity or accumulation of capsid antigen was detected at several days after inoculation. Coinoculation, but not sequential inoculation, of CPMV with similar concentrations of another Comovirus; Cowpea severe mosaic virus (CPSMV), resulted in reduced numbers of CPSMV-induced lesions. This apparent, CPMV-mediated reduction in number of CPSMV-induced infection centers was termed concurrent protection. We report results obtained by inoculating two nearly isogenic cowpea lines derived from a CPMV-susceptible cowpea crossed to Arlington, one line CPMV-susceptible and the other resistant. The CPMV virions B and M, encapsidating genomic RNAs 1 and 2, respectively, were extensively purified by gradient centrifugation. In the CPMV-resistant cowpea, either CPMV or CPMV B affected concurrent protection against CPSMV and against two distinct non-Comoviruses: Cherry leafroll virus and Southern bean mosaic virus. Adding CPMV M to the inoculum did not enhance CPMV-B-mediated protection. CPMV B was ineffective in protecting CPMV-susceptible cowpea. We postulate that CPMV-mediated concurrent protection is elicited in CPMV-resistant cowpea by a CPMV RNA-1-encoded factor and acts to reduce accumulation or spread of CPMV and certain coinoculated challenging viruses in or from the inoculated cell. Coinoculated CPMV did not protect CPMV-resistant cowpea against Tomato bushy stunt virus or Cucumber mosaic virus.

Risk of influenza A (H5N1) infection among health care workers exposed to patients with influenza A (H5N1), Hong Kong

The first outbreak of avian influenza A (H5N1) occurred among humans in Hong Kong in 1997. To estimate the risk of person-to-person transmission, a retrospective cohort study was conducted to compare the prevalence of H5N1 antibody among health care workers (HCWs) exposed to H5N1 case-patients with the prevalence among nonexposed HCWs. Information on H5N1 case-patient and poultry exposures and blood samples for H5N1-specific antibody testing were collected. Eight (3.7%) of 217 exposed and 2 (0.7%) of 309 nonexposed HCWs were H5N1 seropositive (P=.01). The difference remained significant after controlling for poultry exposure (P=.01). This study presents the first epidemiologic evidence that H5N1 viruses were transmitted from patients to HCWs. Human-to-human transmission of avian influenza may increase the chances for the emergence of a novel influenza virus with pandemic potential.

Antibody response in individuals infected with avian influenza A (H5N1) viruses and detection of anti-H5 antibody among household and social contacts

The first documented outbreak of human respiratory disease caused by avian influenza A (H5N1) viruses occurred in Hong Kong in 1997. The kinetics of the antibody response to the avian virus in H5N1-infected persons was similar to that of a primary response to human influenza A viruses; serum neutralizing antibody was detected, in general, >/=14 days after symptom onset. Cohort studies were conducted to assess the risk of human-to-human transmission of the virus. By use of a combination of serologic assays, 6 of 51 household contacts, 1 of 26 tour group members, and none of 47 coworkers exposed to H5N1-infected persons were positive for H5 antibody. One H5 antibody-positive household contact, with no history of poultry exposure, provided evidence that human-to-human transmission of the avian virus may have occurred through close physical contact with H5N1-infected patients. In contrast, social exposure to case patients was not associated with H5N1 infection.

Trends in human immunodeficiency virus (HIV) counseling, testing, and antiretroviral treatment of HIV-infected women and perinatal transmission in North Carolina

Since 1993, trends in perinatal human immunodeficiency virus (HIV) transmission have been monitored by use of chart review of patients identified at a central diagnostic laboratory. In the population studied, either pre- or postnatal antiretroviral therapy to the infant increased from 21% in 1993 to 95% in 1997. Concurrently, the number of HIV-infected infants declined from 25 in 1993 to 4 in 1997. The complete Pediatric AIDS Clinical Trials Group Protocol 076 regimen was the most effective in reducing transmission (3.1%). Twenty-two of 35 infants who became infected in 1995-1997 had mothers who did not receive antiretroviral therapy, although counseling practices improved with time. In 1995, 87% of the mothers of HIV-seropositive infants were counseled, whereas in 1997, 96% were counseled (P<.005). None of 59 infants tested had high-level phenotypic zidovudine resistance, although 5 (8.8%) of 57 infants had virus isolates with at least one mutation in the reverse transcriptase gene associated with reduced phenotypic susceptibility to zidovudine.

Detection of antibody to avian influenza A (H5N1) virus in human serum by using a combination of serologic assays

From May to December 1997, 18 cases of mild to severe respiratory illness caused by avian influenza A (H5N1) viruses were identified in Hong Kong. The emergence of an avian virus in the human population prompted an epidemiological investigation to determine the extent of human-to-human transmission of the virus and risk factors associated with infection. The hemagglutination inhibition (HI) assay, the standard method for serologic detection of influenza virus infection in humans, has been shown to be less sensitive for the detection of antibodies induced by avian influenza viruses. Therefore, we developed a more sensitive microneutralization assay to detect antibodies to avian influenza in humans. Direct comparison of an HI assay and the microneutralization assay demonstrated that the latter was substantially more sensitive in detecting human antibodies to H5N1 virus in infected individuals. An H5-specific indirect enzyme-linked immunosorbent assay (ELISA) was also established to test children's sera. The sensitivity and specificity of the microneutralization assay were compared with those of an H5-specific indirect ELISA. When combined with a confirmatory H5-specific Western blot test, the specificities of both assays were improved. Maximum sensitivity (80%) and specificity (96%) for the detection of anti-H5 antibody in adults aged 18 to 59 years were achieved by using the microneutralization assay combined with Western blotting. Maximum sensitivity (100%) and specificity (100%) in detecting anti-H5 antibody in sera obtained from children less than 15 years of age were achieved by using ELISA combined with Western blotting. This new test algorithm is being used for the seroepidemiologic investigations of the avian H5N1 influenza outbreak.

Characterization of the surface proteins of influenza A (H5N1) viruses isolated from humans in 1997-1998

Influenza A (H5N1) viruses infected humans in Hong Kong between May and December, 1997. Sixteen viruses, including 6 from fatal cases, were isolated during this outbreak. Molecular analysis of the surface proteins genes encoding the hemagglutinin (HA) and neuraminidase (NA) of these H5N1 isolates, of a subtype not previously known to infect humans, are presented. The 16 human H5 HA sequences contain multiple basic amino acids adjacent to the cleavage site, a motif associated with highly pathogenic avian influenza A viruses. The phylogenetic relationship among both avian and human H5 hemagglutinins indicates that the human isolates are related directly to isolates that circulated among chickens in the live poultry markets in Hong Kong prior to and during the outbreak in humans. HA sequences from the human isolates and a recent chicken isolate represent a separate clade, within which there are two subgroups that are distinguishable antigenically and by the presence of a potential glycosylation site. Likewise the N1 neuraminidases of the human H5 isolates represent a clade that is evolutionarily distinct from previously characterized N1 neuraminidases. The recent human H5N1 virus NA genes are avian-like, indicating direct introduction from an avian source rather than evolution of a human N1 NA. All of the 16 human NA genes encode a shortened stalk due to a 19-amino acid deletion, also found in the recent avian H5N1 isolates from Hong Kong. Two unique amino acids were identified in the N1 NAs of the recent human isolates; however, it is not known if these residues influence host range. Neither the HA nor the NA genes of the human H5N1 virus isolates show evidence of adaptive changes during the outbreak. Although analyses of the surface protein genes of the H5N1 viruses from this outbreak did not provide immediate answers regarding the molecular basis for virulence, the analyses provided clues to potentially important areas of the genes worth further investigation.

Obstetricians' knowledge and attitudes toward epidural analgesia in labour

A survey of all registered obstetrician/gynaecologists in Western Australia (n = 79) was conducted to obtain information regarding their level of knowledge about epidural analgesia (EA) in labour and its complications, their sources of information about EA, and their opinions regarding its role in labour and effect on progress of labour. Response rate was 68%. Most respondents had only received lectures about EA after specialist training and 20% did not achieve an adequate knowledge score. Those of less than five years' experience achieved significantly better scores. Over a third did not favour EA in labour until active labour was established, though 90% would recommend it by late first stage in those with a potentially complicated delivery. For women with cardiac or significant medical disease aggravated by labour, 18% would wait until the late first or second stage before suggesting EA. Seventy-seven per cent believed EA prolonged the second stage of labour, though opinion varied regarding EA effects on the duration and progress of first and third stages. Up to thirty minutes delay before epidural placement is acceptable to 87%. This survey suggests that there is both a demand and a need for greater education about EA in labour, particularly with respect to EA side-effects, complications and effects on labour, in the subgroup of obstetricians who have been in obstetric practice more than five years.

Labour ward midwifery staff epidural knowledge and practice

A survey was conducted amongst labour ward midwives at our hospital to evaluate education, knowledge and attitudes toward the management of epidural analgesia in labour. Sixty of 80 distributed forms were returned, giving a 75% response rate. Forty-two per cent of respondents had more than ten years' practice experience. Only 51% achieved a predetermined pass score for knowledge about epidural analgesia. Though most had received formal education about epidural analgesia, 35% felt postgraduate education was insufficient. A majority of midwives supported epidural analgesia on demand (78%), during established labour (74%), or for women at increased risk of caesarean section (82%). Midwives with lower knowledge levels were more likely to recommend epidural analgesia early in labour to multiparous women (P = 0.001) and to women with either a small or a large baby (P = 0.06). The majority of midwives (93%, 70% and 65%) would "almost always" top-up women with cardiac or medical diseases, multiple pregnancy or hypertensive disease, respectively. A clear requirement for ongoing education, with input from the anaesthetic department, was identified, irrespective of personal experience. Practice patterns are discussed and recommendations made with respect to improvement of epidural analgesia management and continuing education.

High prevalence of hepatitis C virus genotype 6 among certain risk groups in Hong Kong

The genotype of hepatitis C virus (HCV) of 172 HCV-RNA positive serum specimens taken from patients with chronic liver diseases, thalassaemia major, chronic renal failure (CRF), haemophilia and intravenous drug abusers (IVDA) was determined by analysis of the amplified 5'UTR region by genotype-specific oligonucleotide probes and restriction fragment length polymorphism (RFLP). Six different genotypes and subtypes (1a, lb, 2, 3, 4 and 6) were found. Genotype lb was the predominant genotype among patients with chronic liver diseases (69.6%), followed by genotype 6 (18.8%), which was similar to that reported for blood donors in earlier studies. Pronounced differences in the distribution of genotypes were seen between the four risk groups. Patients with CRF had a similar distribution to those with chronic liver diseases, whilst the greatest diversity of genotypes was seen in patients with haemophilia, which was expected since they were given factor VIII manufactured overseas. Genotype 6 was particularly prominent in patients with thalassaemia major (50%) and IVDA (62.5%). It is possible that clonal spread of HCV genotype 6 has taken place among a closed subset of the population in Hong Kong through intravenous drug abuse.

Characterization of an avian influenza A (H5N1) virus isolated from a child with a fatal respiratory illness

An avian H5N1 influenza A virus (A/Hong Kong/156/97) was isolated from a tracheal aspirate obtained from a 3-year-old child in Hong Kong with a fatal illness consistent with influenza. Serologic analysis indicated the presence of an H5 hemagglutinin. All eight RNA segments were derived from an avian influenza A virus. The hemagglutinin contained multiple basic amino acids adjacent to the cleavage site, a feature characteristic of highly pathogenic avian influenza A viruses. The virus caused 87.5 to 100 percent mortality in experimentally inoculated White Plymouth Rock and White Leghorn chickens. These results may have implications for global influenza surveillance and planning for pandemic influenza.

Ca2+-channel-dependent and -independent inhibition of exocytosis by extracellular ATP in voltage-clamped rat adrenal chromaffin cells

Membrane currents and capacitance were measured to examine the effects of extracellular ATP on exocytosis in voltage-clamped rat adrenal chromaffin cells. ATP reversibly inhibited Ca2+ current (ICa) and exocytosis. The dependency of exocytosis on ICa evoked by 1-s depolarizations was determined. However, inhibition of exocytosis was 2.6 times larger than that estimated from the reduction of ICa, implying the existence of a Ca2+-channel-independent pathway. This inhibition did not rely on a further reduction of the intracellular Ca2+ concentration spike. ATP reduced the rate of exocytosis induced by clamping the intracellular Ca2+ concentration. Pertussis toxin blocked the inhibitory effects of ATP on ICa and exocytosis. Although RB-2, a P2Y antagonist, blocked the inhibitory effect of ATP on ICa, RB-2 itself produced large increase or decrease in membrane capacitance. Adenosine inhibited ICa via a pertussis-toxin-sensitive pathway but did not significantly inhibit exocytosis. Our data show that extracellular ATP inhibits exocytosis via inhibition of ICa by activation of a pertussis-toxin-sensitive G-protein linked to P2Y receptors. Furthermore, our data strongly suggest that ATP activates another pathway, which is also G-protein dependent and accounts for the majority of the inhibitory effect of ATP on exocytosis.

Sera from amyotrophic lateral sclerosis patients reduce high-voltage activated Ca2+ currents in mice dorsal root ganglion neurons

This study investigated the effects of sera from amyotrophic lateral sclerosis (ALS) patients on high voltage activated (HVA) Ca2+ current in mice dorsal root ganglion (DRG) cells using whole-cell voltage-clamp method. Mice were injected with sera from healthy adults, from patients with other neurological diseases, and from patients with the sporadic form of ALS, for a period of 3 days. Sera from five of six ALS patients reduced HVA Ca2+ current amplitude. The peak Ca2+ current was significantly reduced by ALS sera while the sera from healthy adults and patients with other diseases did not alter Ca2+ current. The inactivation kinetics was altered by ALS sera, and the half-inactivation voltage shifted to more negative potential in ALS group. These results suggest that sporadic ALS serum factors may exert interactions with the HVA Ca2+ channel in DRG cells to reduce the Ca2+ current.

Postoperative epidural infusion: a randomized, double-blind, dose-finding trial of clonidine in combination with bupivacaine and fentanyl

The aim of this randomized, double-blind trial of postoperative thoracic epidural analgesic infusions was to determine whether clonidine at 10 microg/h (group C10, n = 22), 15 microg/h (Group C15, n = 24), or 20 microg/h (Group C20, n = 24) improved postoperative analgesia in patients undergoing abdominal gynecologic surgery, without side effects or hemodynamic changes, when added to a 5-mL/h infusion of 0.125% bupivacaine and fentanyl 2 microg/mL (Group CO, n = 22). The 24-h study infusion was supplemented, as required, by patient-controlled epidural fentanyl. Groups were similar for age, weight, duration, and type of surgery. Clonidine produced a dose-dependent improvement in analgesia at rest. Only 20 microg/h significantly increased the percentage of patients who experienced no pain with coughing (relative risk 1.44, 95% confidence interval 1.24-1.94), reduced pain scores with coughing (P < 0.05), and significantly lowered supplementary fentanyl requirements (P < 0.05). Groups were similar for sedation, pruritus, nausea, time to ambulation, and satisfaction with analgesia. Clonidine produced a dose-dependent decrease in blood pressure and pulse rate and an increase in vasopressor requirement (P < 0.01). Epidural clonidine infused at 20 microg/h improves analgesia during coughing when combined with epidural bupivacaine-fentanyl in patients undergoing lower abdominal surgery but is associated with hemodynamic changes and increased vasopressor requirement.

Hippocampal volumetry with magnetic resonance imaging: a cost-effective validated solution

PURPOSE

The clinical utility of hippocampal volumetry is well documented, but the materials and techniques required to perform the procedure are not widely available outside major research centers. We describe a personal computer-based method of volumetric data analysis.

METHODS

Using a 1.0-T scanner, we obtained 2-mm-thick tilted coronal MPRAGE magnetic resonance imaging (MRI) scans of 20 healthy volunteers aged 20-38 years. We used an inexpensive utility program to extract image information and an NIH Image for image analysis. The hippocampal formations were traced with a graphics tablet and landmarks described by Watson et al. (Neurology 1992;42:1743-50). Overlays of individual observers' tracings were used to fine tune the selection of landmarks and boundaries. Filled-in silhouette pairs generated from these "training tracings" were compared to determine how well observers could visually quantify area differences.

RESULTS

Visual detection of asymmetry of silhouette pairs was sensitive, but the magnitude of asymmetry was underestimated. We achieved intraobserver coefficients of variation of right/left volume ratios between 0.82 and 3.16 and an interobserver range of volume ratios of 6%. In 20 healthy controls aged 20-38 years, the mean right and left hippocampal volumes were 2,911 mm3 and 2,836 mm3, respectively. The lower limits of normal were 2,217 mm3 for the right and 2,178 mm3 for the left. The mean right/left hippocampal ratio was 1.03, and the limits of normal (3 SD) for this were 0.95 to 1.10.

CONCLUSIONS

Hippocampal volumetry can be performed reliably and economically. Our methodology makes it possible for different observers to generate consistent and comparable measurements.

Perinatal HIV infection and the effect of zidovudine therapy on transmission in rural and urban counties

OBJECTIVES

To assess health care providers' identification of human immunodeficiency virus (HIV)-exposed infants, to ascertain the prevalence of transplacental or oral zidovudine treatment among infants exposed to HIV, and to estimate the impact of zidovudine use on perinatal transmission in rural and urban North Carolina.

DESIGN

Survey of North Carolina newborns tested for HIV infection in 1993 and 1994 compared with the number of anonymous HIV-positive childbearing women.

SETTING

North Carolina hospitals, public health clinics, and private physicians' offices.

MAIN OUTCOME MEASURES

Rates of identification of HIV-exposed infants and of perinatal HIV-1 transmission, determined by HIV culture and polymerase chain reaction testing in the infants.

RESULTS

The proportion of HIV-exposed children in North Carolina who were identified and tested increased from 60% in 1993 to 82% for all of 1994, and to more than 90% for the last quarter of 1994. The HIV-exposed infants born in rural counties were more likely to be recognized than those born in urban counties (P<.001). In 1994, most infants were evaluated relatively early in life: 39% by 1 week of age, 63% by 6 weeks, and 76% by 3 months. Among infants with recognized HIV exposure, transmission decreased significantly between 1993 and 1994, from 21% to 8.5%, respectively (P=.009). After the announcement of the results of the AIDS Clinical Trials Group Protocol 076, zidovudine was given to 75% of HIV-positive women who delivered infants in North Carolina. Only 5.7% of infants who received any zidovudine became infected, compared with 18.9% of infants who received no zidovudine (P=.007).

CONCLUSIONS

Health care providers in North Carolina are identifying most of the state's HIV-seropositive pregnant women, treating them with zidovudine, and testing their infants soon after birth for HIV infection. The use of zidovudine in pregnant women and their infants has reduced perinatal HIV transmission in the state.

Depressor pathway involved in somatosympathetic reflex in cats

The present study aimed to identify direct vasodepressor pathways from the rostral ventrolateral medulla (RVLM) to the spinal cord and their role in mediation of somatosympathetic reflexes. Vasopressor and depressor areas were identified by stimulating various sites of RVLM electrically and/or chemically in anesthetized cats. Electrical lesions on the pressor areas abolished the pressor response evoked by peripheral C-fiber activation while the depressor response remained. Electrical lesions on the depressor areas decreased the depressor response evoked by A delta-fiber stimulation. To characterize the neurons involved, 17 medullospinal sympathetic neurons were identified electrophysiologically. While most of them were sympathoexcitatory, three medullospinal tract cells were found to be sympathoinhibitory neurons. From these results we concluded that a minor group of neurons in the RVLM is sympathoinhibitory and is involved in mediation of somatosympathetic depressor response.

The primary antibody repertoire of normal, immunodeficient and autoimmune mice is characterized by differences in V gene expression

During the last decade, the structure and organization of the immunoglobulin heavy and light chain locis have been defined in mice and humans. Studies on VH gene expression at different stages of development, in different organs and disease states have provided useful insight into the construction of a primary antibody repertoire in mice. Clearly, 3'VH genes 7183, Q52 and Vh11, which are conserved during evolution, are preferentially expressed during early development of the B-lymphocyte repertoire. A preferential use for the V kappa 4 gene family is evident during early B-cell development. The initial development of the primary antibody repertoire is therefore influenced by a restricted set of VH and V kappa gene elements. The restricted B-cell repertoire is subsequently normalized in the periphery, as revealed by stochastic VH gene expression, as a result of exposure to environmental antigens. Obviously, the peripheral B-cell pool characterized by stochastic VH gene expression is selectively replenished by newly generated B cells in bone marrow that preferentially expresses 3'VH genes. The V kappa genes are, however, expressed in a non-random manner in the neonatal and adult B-lymphocyte repertoire that is probably related to VH and V kappa association dynamics and/or positive or negative selection. Interestingly, these characteristics of neonatal and adult primary repertoire are noted in both B1 and B2 lymphocytes. No remarkable age-related differences are evident for VH and V kappa gene expression. In healthy mice, both the mitogen responsive (available) and unstimulated (expressed) B-cell repertoire show similar VH gene expression. Interestingly, VH gene expression varies in different organs which may reflect, or occur as a result of, the specialized function of each organ. For example, J558 gene expression is higher in the peripheral LN where B cells continuously encounter exogenous antigens. The skewed VH and V kappa gene expression noted in immunodeficient and autoimmune lupus-prone mice reflects the impairment of the primary antibody repertoire associated with immunodeficiency and autoimmune disorders.

Mechanism of liposome destabilization by polycationic amino acids

Polycationic amino acids induce the leakage and fusion of liposomes containing anionic lipids. We have investigated the nature and extent of the changes in membrane physical properties caused by these polypeptides which could result in the observed membrane destabilization. We found that in the range of pH 5 to pH 7 both poly-L-histidine and poly-L-lysine were ineffective in shifting the bilayer to hexagonal phase transition temperature of dielaidoylphosphatidylethanolamine, either in the presence of absence of 1-palmitoyl-2-oleoylphosphatidylserine. We also studied the gel to liquid crystalline phase transition properties of 1:1 mixtures of phosphatidylserine and phosphatidylethanolamine, both in dimyristoyl forms as well as the 1-palmitoyl-2-oleoyl forms, as a function of pH and in the presence and absence of polycationic amino acids. We observed that these two lipids were largely miscible at all pH values and in the presence and absence of the polypeptides. However, there was some increased tendency for phase separation at higher pH and in the absence of polypeptide. Thus neither changes in curvature strain nor lateral phase separation induced by the polycationic amino acids could account for their marked ability to induce leakage and fusion. Phosphatidylethanolamine labelled with pyrene on one of the acyl chains gives rise to fluorescent emission from both monomer and excimer forms. The ratio of emission intensity from these two forms is indicative of lateral phase separation and the degree of lateral mobility of this probe. In equimolar mixtures of the 1-palmitoyl-2-oleoyl forms of phosphatidylserine and phosphatidylethanolamine in the liquid crystalline phase at 30 degrees C we find little effect of pH on the ratio of excimer to monomer emission intensity. However poly-L-lysine markedly lowers the fraction of excimer emission from these liposomes through the pH range from 5 to 7. Poly-L-histidine lowers the excimer to monomer emission ratio at pH 5 but not at pH 7. This is opposite to what one would expect for lateral phase separation and is interpreted at being the consequence of the polypeptide lowering the rate of lateral diffusion of the lipids. This effect of poly-L-histidine is observed over a range of temperatures from 0 to 40 degrees C in both gel and liquid crystalline phases. There is no evidence from the behaviour of the pyrene fluorescent probe for lipid interdigitation.(ABSTRACT TRUNCATED AT 400 WORDS)

Contribution of L- and N-type calcium currents to exocytosis in rat adrenal medullary chromaffin cells

The excitation-secretion coupling process requires Ca2+ influx through voltage-dependent Ca2+ channels (VDCC) but the contribution of L-type or N-type VDCC during the secretion from adrenal chromaffin cell is still on debate. In this study we explored the contribution of each VDCC to exocytosis in single rat adrenal chromaffin cells. Chromaffin cells were voltage-clamped clamped in the whole-cell recording mode. Ca2+ inward current (ICa) was elicited by depolarization from -70 mV to +10 mV and the change in cell membrane capacitance (Cm) was monitored as an indicator of the resultant exocytosis. The increase in Cm had positive correlation with the amount of ICa and replacing the internal Ca2+ buffer to high EGTA (5 mM) decreased the sensitivity of Cm increase to Ca2+ influx. After blockage of ICa with 100 microM Cd2+, there was no increase in Cm following membrane potential depolarization while INa was intact. To clarify the contribution of each type of VDCC to induce exocytosis during membrane potential depolarization, L- and N-type ICa were blocked selectively by Ca2+ channel antagonists. After blockage of L-type ICa with nicardipine (1 microM), ICa was blocked to 35 +/- 6.2% (mean +/- standard error) of control and the resultant change in Cm was reduced to 38 +/- 4.6% of control. Bay K-8644 (1 microM) enhanced ICa and the similar proportion of Cm was increased by this L-type VDCC agonist. On the other hand omega-conotoxin GVIA (1 microM), an N-type VDCC antagonist, blocked ICa to 60 +/- 4.3% of control and reduced the change in Cm to 58 +/- 3.9% of control.(ABSTRACT TRUNCATED AT 250 WORDS)

HIV infection in pregnancy. A review of current developments

It appears that pregnancy itself is not adversely affected by HIV infection, but the course of HIV infection in the mother may be accelerated by pregnancy. The results of the 076 trial have changed our approach to AIDS in pregnancy. Heretofore AZT was only given for maternal indications such as severe immunodeficiency (CD4 count less than 200). We now recommend that AZT be given to all women with HIV infection and to infants postpartum. As to mode of delivery, Cesarean section may be beneficial, but we await further studies. We strongly encourage all pregnant women to have HIV testing regardless of risk factors. The HIV epidemic is here, in North Carolina. It is our responsibility as doctors to help pregnant women as best we can with their disease.

Prevalence of hepatitis C infection in Hong Kong

A study of a cross-section of the Hong Kong Chinese population was done to investigate the seroprevalence of hepatitis C. Healthy subjects were random visitors of a health exhibition, while clinical subjects were recruited from an outpatient liver disease clinic, sexually transmitted disease clinics, dialysis centres and drug rehabilitation centres. A total of 910 subjects were tested. The assay kits were from Abbott and Ortho laboratories. Of the general population, 0.5% was found to be positive for antibody to hepatitis C (anti-HCV). Suspected chronic non-A non-B patients, parenteral drug abusers and haemophiliacs shared a common high (up to 70%) prevalence of anti-HCV. Sexual partners of index patients, homosexuals and female prostitutes as well as hepatitis B carriers had 0% prevalence. It was concluded that parenteral and blood product exposures were the two main risk factors for hepatitis C.

Histoplasma capsulatum infection associated with continuous ambulatory peritoneal dialysis

Fungal infection has become increasingly more important in patients undergoing continuous ambulatory peritoneal dialysis. We report here a case of Histoplasma capsulatum infection in such a Hong Kong Chinese patient who presented with fever and peritonitis. Histoplasma capsulatum was isolated from the dialysis fluid and histoplasma antibody was detected in the serum. The patient responded to the combined treatment of fluconazole, 5-flurocytosine and amphotericin B. This is the first reported case of histoplasmosis in Hong Kong.

An investigation of maternal morbidity with identification of life-threatening 'near miss' episodes

This study was designed to investigate the pattern of obstetric morbidity and to determine the frequency of serious life-threatening episodes as a basis for clinical audit. The records of over 2,000 maternities from a National Health Service Consultant Unit during a six-month period were analysed. Morbidity was noted in almost a quarter of the cases, and life-threatening episodes, termed 'near miss' morbidity, were identified. As the maternal death rate has fallen in this country, maternal morbidity has come to represent a more useful indicator of obstetric care than mortality. The results of this study identify the need for an agreed set of definitions for 'near miss' morbidity, and suggest that not only should it be included for discussion in unit perinatal meetings, but that Regional obstetric morbidity enquiries would provide valuable denominator data on morbidity.

Skin diseases in children with HIV infection and their association with degree of immunosuppression

Since the recognition of the acquired immunodeficiency syndrome (AIDS) in 1981, several dermatologic manifestations have been associated with the syndrome, including candidiasis, dermatophyte infection, molluscum contagiosum, herpes simplex and zoster, bacterial infection, and malignancy. Skin diseases have been observed in both the adult and the pediatric human immunodeficiency virus (HIV) infection in an academic hospital setting in relationship to the current CDC classification of pediatric HIV infection. The severity of dermatologic manifestations is correlated with the immune status of the patients. The latter was determined by T4 helper cell numbers and lymphoproliferative responses to mitogens and recall antigens. More severe T helper cell depletion was associated with a wider spectrum and increased severity of dermatologic manifestations.

In vitro synthesis of human immunodeficiency virus-specific antibodies in peripheral blood lymphocytes of infants

An assay system was developed for the analysis of antibodies secreted in vitro against human immunodeficiency virus (HIV) by cultured peripheral blood lymphocytes of HIV-infected individuals. Cultures of peripheral blood lymphocytes were established with medium alone or with medium containing Epstein-Barr virus (EBV) or pokeweed mitogen. HIV antibodies were determined by an ELISA performed with commercial kits in which a whole virus extract served as antigen. Optimal antibody secretion was detected in 7-day peripheral blood lymphocyte cultures to which EBV had been added to provide polyclonal B-cell activation. Pokeweed mitogen-induced antibody secretion and spontaneous antibody secretion were less consistent. With EBV as a stimulus, the sensitivity and specificity of this assay for determining HIV infection status were each 100% in adults. When the assay was applied to infants and children, 23 of 24 symptomatic HIV-seropositive children (class P-2) and 11 of 33 asymptomatic seropositive infants aged less than or equal to 15 months (class P-0) tested positive for EBV-induced antibody secretion. Six of the 11 P-0 patients who tested positive have progressed to develop symptomatic disease, while the remainder are still seropositive at ages 2-15 months. Of the infants who were negative in this assay, all have remained asymptomatic. Treatment with 3'-azido-3'-deoxythymidine in infected adults and children has resulted in transient suppression of the in vitro antibody response in some instances. Thus EBV-induced synthesis of HIV-specific antibodies in vitro is a sensitive and specific indicator of HIV infection and is of help in determining infection status of asymptomatic seropositive infants who are classified as having "indeterminate" infection.

Multiple ischemic infarcts in a child with AIDS, varicella zoster infection, and cerebral vasculitis

A 4 1/2-year-old girl with acquired immunodeficiency syndrome and prolonged varicella zoster virus skin infection developed multiple ischemic strokes and radiologic and histopathologic evidence of central nervous system vasculitis. Typical features of acquired immunodeficiency syndrome encephalitis were not present and there was no evidence of vasculitis outside the nervous system. Central nervous system vasculitis probably resulted from varicella zoster virus infection that persisted because of immunodeficiency. This acquired immunodeficiency syndrome complication has only rarely been described in adults and to our knowledge has not been described in children.

Continuous varicella-zoster infection associated with acyclovir resistance in a child with AIDS

Acyclovir has become the treatment of choice for varicella-zoster virus (VZV) infections in immunocompromised individuals. This article describes a 4-year-old girl congenitally infected with human immunodeficiency virus who developed a continuous cutaneous infection with VZV that persisted over a 14-month period until her death. Initial episodes of varicella and zoster were responsive to acyclovir treatment; however, subsequent recurrences necessitated administration of multiple courses of acyclovir. Lesions became markedly hyperkeratotic, slow healing, and persistent despite acyclovir therapy. Numerous attempts to isolate virus from the lesions yielded only one isolate late in the course of therapy. This virus clearly demonstrated acyclovir resistance in vitro. Bizarre manifestations of VZV infection could present both diagnostic and therapeutic dilemmas. Prolonged acyclovir treatment of highly immunocompromised patients with acquired immunodeficiency syndrome and severe VZV may lead to the appearance of resistant virus.

Penicillium marneffei infection: an underdiagnosed disease?

Penicillium marneffei is a rare human pathogen that often causes problems in clinical and histological diagnosis. A patient who presented with autoimmune haemolytic anaemia and hepatosplenomegaly, and was subsequently found to be suffering from disseminated Penicillium marneffei infection, is reported. The liver biopsy showed epithelioid cell granulomas only, and tuberculosis was initially considered the most likely diagnosis. The correct diagnosis became evident in a subsequent colonic biopsy, which showed extensive infiltration by penicillium-laden macrophages.

The problem of home management in the estimation of the incidence of acute myocardial infarction from hospital records

Past studies of the incidence of acute myocardial infarction (AMI) have found information for patients managed at home difficult and expensive to obtain. This study attempted to find whether the efficiency of gathering this information could be improved, or if this group of patients could be neglected entirely. A random sample of 270 doctors in Perth were asked about their management of cases of suspected AMI at home. Of these doctors, 78% said that they never managed AMI at home; excluding such doctors before seeking voluntary notification of new cases managed at home could make population surveys of AMI more efficient. For patients under 65 it was estimated that about 1% or less of non-fatal cases meeting World Health Organization criteria for definite AMI were managed at home. Thus neglecting this group would probably cause little bias in computing incidence rates for AMI in Perth.