Fluorescence imaging of GABAA receptor-mediated intracellular [Cl-] in P19-N cells reveals unique pharmacological properties

This study describes the pharmacological properties of GABAA receptors expressed in P19-N cells using fluorescence imaging of intracellular chloride with 6-methoxy-N-ethylquinolinium iodide (MEQ). We show that application of the GABA agonist, muscimol (10-200 microM), produces time- and concentration-dependent increases in intracellular [Cl-] that are blocked by bicuculline. Diazepam (10 microM) and pentobarbital (1 mM) potentiate muscimol-stimulation. These receptors exhibit novel pharmacological properties. The neurosteroid, 3alpha-hydroxy-5alpha-pregnane-20-one (1-10 microM) exhibited weak potency in enhancement of muscimol-stimulation. Ethanol (50 and 100 mM) exhibited high efficacy on muscimol responses, a 4- to 5-fold potentiation, respectively, of muscimol (10 microM) alone. GABA and muscimol allosterically modulated specific binding of [3H]flunitrazepam to differentiated P19 cells. Modulation of GABAA receptor mediated increases in intracellular [Cl-] demonstrated stability in response magnitude from 7 to 15 days following removal of retinoic acid. In concert, GABAA receptor subunit mRNA and protein expression patterns in these neuron-like cells were stable over the same period. Using RT-PCR we determined that differentiated P19 cells lack gamma1, gamma2L, alpha6 and delta subunit mRNAs while expressing alpha1, alpha2, alpha3, alpha4, alpha5, beta1, beta2, beta3, gamma2S and gamma3. Furthermore, subunit specific antibody immunocytochemical labeling of cells with a neuronal morphology indicated the presence of alpha1, alpha2, alpha4, and gamma2 subunits (the only subunits tested). Therefore, P19-N cells should prove useful to researchers in need of a model cell culture system in which to study function and regulation of neuronal GABAA receptors.

Efficacy of home-based peer counselling to promote exclusive breastfeeding: a randomised controlled trial

BACKGROUND

Exclusive breastfeeding is recommended worldwide but not commonly practised. We undertook a randomised controlled study of the efficacy of home-based peer counselling to increase the proportion of exclusive breastfeeding among mothers and infants residing in periurban Mexico City.

METHODS

Two intervention groups with different counselling frequencies, six visits (44) and three visits (52), were compared with a control group (34) that had no intervention. From March, 1995, to September, 1996, 170 pregnant women were identified by census and invited to participate in the study. Home visits were made during pregnancy and early post partum by peer counsellors recruited from the same community and trained by La Leche League. Data were collected by independent interview. Exclusive breastfeeding was defined by WHO criteria.

FINDINGS

130 women participated in the study. Only 12 women refused participation. Study groups did not differ in baseline factors. At 3 months post partum, exclusive breastfeeding was practised by 67% of six-visit, 50% of three-visit, and 12% of control mothers (intervention groups vs controls, p<0.001; six-visit vs three-visit, p=0.02). Duration of breastfeeding was significantly (p=0.02) longer in intervention groups than in controls, and fewer intervention than control infants had an episode of diarrhoea (12% vs 26%, p=0.03).

INTERPRETATION

This is the first reported community-based randomised trial of breastfeeding promotion. Early and repeated contact with peer counsellors was associated with a significant increase in breastfeeding exclusivity and duration. The two-fold decrease in diarrhoea demonstrates the importance of breastfeeding promotion to infant health.

Gender-selective effects of ethanol dependence on NMDA receptor subunit expression in cerebral cortex, hippocampus and hypothalamus

Previous investigations have shown subunit-selective alterations in NMDA receptors in ethanol dependent male rats. In the present study, we found pronounced gender differences in the effects of ethanol dependence on NMDA receptor subunit expression in all brain regions investigated. Ethanol dependent female rats exhibited increased NR1 subunit levels in cerebral cortex and hypothalamus, whereas males displayed increased NR1 levels only in hippocampus. NR2A subunit levels were significantly increased only in hippocampus from ethanol dependent male rats, whereas NR2B subunit levels significantly increased in cerebral cortex of both female and male rats. These findings suggest that gender influences neuroadaptations elicited by ethanol dependence at the level of NMDA receptor subunit expression.

Rapid ethnographic assessment of breastfeeding practices in periurban Mexico City

Before carrying out a breastfeeding promotion programme in a periurban area of Mexico City, we conducted a rapid ethnographic study to determine the factors associated with absence of exclusive breastfeeding. The responses to pilot interviews were used to develop a standardized questionnaire regarding reasons for infant feeding choice, sources of advice, and barriers to breastfeeding. We interviewed a random sample of 150 mothers with a child < 5 years of age; 136 (91%) of them had initiated breastfeeding; but only 2% exclusively breastfed up to 4 months. The mothers consistently stated that the child's nutrition, health, growth, and hygiene were the main reasons for the type of feeding selected; cost, comfort, and the husband's opinion were less important. Physicians were ranked as the most important source of advice. Reduction or cessation of breastfeeding occurred on the doctor's advice (68%); or when the mothers encountered local folk illnesses such as "coraje" (52%) or "susto" (54%), which are associated with anger or fright; or had "not enough milk" (62%) or "bad milk" (56%); or because of illness of the mother (56%) or child (43%). During childhood illnesses and conditions, breastfeeding was reduced and the use of supplementary foods was increased. This study emphasizes the importance of cultural values in infant feeding choices, defines specific barriers to breastfeeding, and provides a basis for interventions to promote exclusive breastfeeding in the study population.

Effects of chronic ethanol consumption and withdrawal on the neuroactive steroid 3alpha-hydroxy-5alpha-pregnan-20-one in male and female rats

Prolonged alcohol (ethanol) consumption leads to the development of alcohol tolerance and cross-tolerance to some benzodiazepines and barbiturates. In contrast, rats undergoing alcohol withdrawal are sensitized to the anticonvulsant effects of the endogenous GABA(A) receptor modulator, 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP). Alterations in endogenous, cerebral cortical levels of 3alpha,5alpha-THP during alcohol withdrawal could contribute to the observed sensitization to 3alpha,5alpha-THP. Therefore, this study investigated plasma and brain levels of 3alpha,5alpha-THP, progesterone, and corticosterone during alcohol dependence and withdrawal in the rat. Plasma corticosterone, progesterone (a precursor of 3alpha,5alpha-THP) and 3alpha,5alpha-THP levels were unchanged in alcohol-dependent animals. Cerebral cortical levels of 3alpha,5alpha-THP decreased in dependent male animals, but not in dependent female rats. During alcohol withdrawal, plasma corticosterone and progesterone levels increased in male, but not female rats. However, neither plasma nor cerebral cortical 3alpha,5alpha-THP levels were altered from control levels in male or female rats during alcohol withdrawal. Plasma and brain levels of 3alpha,5alpha-THP were markedly higher in female compared with male rats. Cerebral cortical levels of 3alpha,5alpha-THP during the diestrus phase of the estrus cycle were approximately 4 to 6 ng/g, a concentration that may approach physiological relevance. These findings suggest that sensitization to 3alpha,5alpha-THP during alcohol withdrawal is not mediated by elevations in brain levels of endogenous 3alpha,5alpha-THP in male or female rats. However, elevations in circulating corticosterone and progesterone levels during ethanol withdrawal in male rats may underlie gender differences in allopregnanolone sensitivity during ethanol withdrawal.

Immunization coalitions that work: training for public health professionals

Coalition development is a major strategy to increase immunization rates. However, if local and state coalitions are to succeed, their staffs need training and technical assistance in coalition development, community planning, and program implementation. The National Coalition Training Institute trains key health agency staff in 87 state, territorial, and urban sites to perform needs assessments, use data to guide planning, plan comprehensive strategies, and evaluate their coalitions. The curriculum is based on training needs that are identified by a national survey of immunization coalitions, effective approaches, and participant evaluation. According to evaluations conducted during its first year, the National Coalition Training Institute is meeting the needs of participants.

GABA as a trophic factor for developing monoamine neurons

GABA exerts a variety of trophic influences on developing brain cells, as reviewed in this issue. During early stages of brain development, GABAergic axons course through regions where other neurotransmitter phenotypes are being generated. This raises the question of whether GABA may influence the ontogeny of these neurotransmitter systems in the embryonic brain. The brainstem provides a good example of this relationship, since GABAergic axons pass through the anlage of the developing raphe nuclei when serotonergic (5-HT) neurons are just beginning to differentiate and migrate away from the ventricular zone. Evidence that GABA regulates development of these and adjacent noradrenergic neurons has recently been obtained using embryonic brainstem cultures, which contain differentiating 5-HT, tyrosine hydroxylase (TH), and GABA neurons. These cultures also express multiple GABAA-receptor subunits that form functional GABAA/Cl- channels. GABAA receptor ligands produce differential effects on survival and growth of monoamine (5-HT, TH) and GABA neurons, and on expression of GABAA subunits in these cultures. These findings provide evidence that GABA can selectively regulate development of neurons of different neurotransmitter phenotypes, as well as developmental expression of its own receptors, and suggest that in utero exposure to GABAA receptor ligands could produce imbalances in monoaminergic versus GABAergic neurotransmission in the developing brain. Dieldrin, an organochlorine pesticide that acts as a GABAA antagonist, has potent effects on survival, and neurite outgrowth by 5-HT neurons, and GABAA subunit expression in brainstem cultures. Thus, maternal exposure to organochlorine pesticides could pose a risk to fetal brain development, especially during the first trimester of pregnancy.

The role of GABA(A) receptors in the acute and chronic effects of ethanol

GABA(A) receptors are sensitive to ethanol in distinct brain regions and are clearly involved in the acute actions of ethanol, ethanol tolerance, ethanol dependence and ethanol self-administration. Data from a variety of perspectives such as molecular, cellular and behavioral analysis have elucidated the role of GABA(A) receptors in these processes. GABA(A) receptor activation mediates many of the behavioral effects of ethanol including motor incoordination, anxiolysis and sedation. The actions of ethanol at GABA(A) receptors are influenced by endogenous modulators such as the neuroactive steroids. Sensitization to these compounds influences ethanol dependence and withdrawal and may explain gender differences in the molecular effects of ethanol. Furthermore, GABA(A) receptors may also play a role in ethanol self-administration via the mesolimbic reward system. Ethanol tolerance and dependence may be explained, in part, by changes in the function of GABA(A) receptors. We have proposed that alterations in native GABA(A) receptor subunit assembly could alter the functional properties of these receptors. However, post-translational modifications or other post-synaptic mechanisms may also explain changes in GABA(A) receptor function. Genetic animal models of ethanol dependence have also identified GABA(A) receptor genes as likely mediators of the behavioral adaptations associated with ethanol dependence and withdrawal. A better understanding of the effects of ethanol at GABA(A) receptors has highlighted important potential mechanisms involved in the development of alcoholism.

A prospective study of astrovirus diarrhea of infancy in Mexico City

AIM

To describe the epidemiologic and clinical characteristics of astrovirus-associated diarrhea in a cohort of young children from a periurban community in Mexico City.

METHODS

From November, 1988, through December, 1991, a total of 214 children were enrolled in a longitudinal study of diarrhea and monitored from birth to 18 months of age. A stool specimen was collected during each episode of diarrhea. Specimens from a total of 510 diarrhea episodes were tested for astrovirus by enzyme immunoassay and examined for other enteric pathogens. The antigenic types of astrovirus were determined by a typing enzyme immunoassay.

RESULTS

Astrovirus was detected in 26 (5%) of 510 diarrhea episodes, with an incidence rate of 0.1 episode/child year; the highest rate was in children 13 to 18 months of age. Astrovirus-associated diarrhea was characterized by a median of 4 stools (range, 2 to 10) during the first 24 h, a median duration of 3 days (range, 1 to 21), vomiting (20%), and fever (7%). No cases of dehydration or repeat symptomatic infections were observed. Coinfection with another pathogen was detected in 11 of the 26 episodes (42%). Serotype 2 (35%) was most common, followed by serotypes 4 (15%), 3 (11%), and 1 and 5 (4% each); 31% were nontypable. Astrovirus-associated diarrhea was less severe, as measured by the number of stools (4.3 +/- 1.9), than diarrhea caused by rotavirus (7.1 +/- 2.8) or when coinfections occurred (5.5 +/- 1.6; P = 0.008).

CONCLUSIONS

Astrovirus was associated with 5% of the episodes of diarrhea in this cohort of young Mexican children and presented as a mild secretory diarrhea. Five predominant antigenic types were detected with type 2 being the most common.

Methylphenidate in the United States, 1990 through 1995

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Influence of gender on chronic ethanol-induced alterations in GABAA receptors in rats

Ethanol dependence, arising from chronic ethanol exposure, is associated with neuroadaptations of GABAA receptors, evidenced by alterations in various behaviors, receptor responsiveness and subunit gene expression. The present studies explored the effects of ethanol dependence in female rats for comparison with previous studies in our laboratory using male rats. We found that ethanol dependence resulted in differential effects on GABAA receptor gene expression in female rat cerebral cortex compared to ethanol dependent male rats. Notably, chronic ethanol consumption did not change GABAA receptor alpha 1 subunit peptide levels in ethanol dependent female rat cortex, in contrast to previously observed decreases in alpha 1 subunit expression in ethanol dependent male rat cortex. The effects of ethanol dependence on additional GABAA receptor subunit peptide levels (alpha 4, beta 2/3 and gamma 2) were similar, but not identical, between female and male rat cortex. When directly compared within the experiment, male and female rats had similar baseline bicuculline seizure thresholds and displayed a similar increase in seizure susceptibility during ethanol withdrawal. Ethanol withdrawn female rats were cross tolerant to the anticonvulsant effects of diazepam, similar to the findings in ethanol withdrawn male rats. Ethanol withdrawn female rats showed a dose-dependent enhancement of the anticonvulsant effect of the neuroactive steroid, THDOC (3 alpha,21-dihydroxy-5 alpha-pregnan-20-one) compared to control animals. This finding is similar to previous observations of increased sensitivity to the anticonvulsant effect of 3 alpha,5 alpha-THP (3 alpha-hydroxy-5 alpha-pregnan-20-one) in ethanol withdrawn male and female rats. In addition, low dose administration of THDOC elevated seizure thresholds in ethanol withdrawn female but not male rats, suggesting that ethanol withdrawn female rats were more responsive to the anticonvulsant effects of this neurosteroid than were ethanol withdrawn male rats. These findings show that gender impacts on adaptations in GABAA receptors elicited by ethanol dependence. However, the physiological outcomes of the differential alterations are not clear. Taken together, these studies suggest that additional mechanisms, beyond effects on GABAA receptor gene expression are involved in the mediation of ethanol dependence and withdrawal.

GABA(A) receptor alpha1, alpha4, and beta3 subunit mRNA and protein expression in the frontal cortex of human alcoholics

Animal studies have shown that chronic ethanol consumption produces physical dependence upon ethanol and alters gamma-aminobutyric acid-A (GABA(A)) receptor subunit gene expression in brain. Although extensive investigation has been conducted in animal models, relatively little work has been performed directly on human alcoholic brain tissue to determine if there are alterations in GABA(A) receptor gene expression. In this study, GABA(A) receptor alpha1, alpha4, and beta3 subunit mRNA and peptide expression in postmortem frontal cortex from human alcoholics (n = 15) and age- and sex-matched controls (n = 13) were measured by quantitative, competitive reverse transcription polymerase chain reaction and Western blot analysis. GABA(A) receptor beta3 subunit mRNA expression was 35% greater (p < 0.05) in alcoholics, compared with nonalcoholic controls. We found no significant difference in alpha1 and alpha4 subunit mRNA levels between groups. However, there was a trend toward greater (21%) alpha1 subunit mRNA expression. There was no difference in alpha1, alpha4, or beta2/3 subunit peptide levels in frontal cortex between controls and alcoholics. Neither the age of the subjects nor the postmortem interval correlated with mRNA or peptide levels. Blood ethanol content also did not correlate with mRNA or peptide expression in alcoholic samples. These data suggest that GABA(A) receptor adaptations, resulting from prolonged alcohol consumption in human alcoholics, may differ from animal models of alcohol dependence. These differences may be related to the longevity of alcohol exposure in human alcoholics, as well as variability in the dependence/withdrawal state of the human subjects. Therefore, further studies in human postmortem brain tissue are warranted.

Role of human-milk lactadherin in protection against symptomatic rotavirus infection

BACKGROUND

Human milk contains a 46 kDa mucin-associated glycoprotein, lactadherin, which binds specifically to rotavirus and inhibits its replication. This study tested the hypothesis that lactadherin protects against symptoms of rotavirus infection.

METHODS

200 infants in Mexico City were recruited at birth and monitored by regular stool EIA for rotavirus, serology, and recording of feeding and stool patterns. Milk samples were obtained from the mothers weekly until 4 weeks post partum then monthly. The sample taken immediately before an infant's episode of rotavirus infection was assayed for lactadherin, butyrophilin, mucin, and secretory IgA. An infection was defined as symptomatic if diarrhoea occurred in the 5 days before or after detection of the virus.

FINDINGS

31 infants developed rotavirus infection; 15 were symptomatic and 16 had no symptoms. The median concentration of lactadherin in the milk samples (obtained 4-41 days [median 13] before the infection) was 48.4 (range 5.6-180) microg/mL in the asymptomatic group and 29-2 (6.2-103-4) microg/mL in the symptomatic group. Although these medians did not differ significantly, in logistic regression analysis adjusted for age at infection and secretory IgA concentration there was a significant difference between the groups (p=0O01). No association between symptom status and concentrations of butyrophilin, mucin, or secretory IgA was found.

INTERPRETATION

Protection against rotavirus by human milk is associated with the glycoprotein lactadherin. This association is independent of products of the secretory immune system.

CINCH: an urban coalition for empowerment and action. Consortium for the Immunization of Norfolk's Children

CINCH (Consortium for the Immunization of Norfolk's Children) is an urban coalition that was developed in 1993 to improve childhood immunization rates in Norfolk, Virginia. CINCH involves diverse citizens and institutions in effective community-based assessment, planning, and action. A needs assessment from 1993 found that only 49% of Norfolk 2-year-olds were adequately immunized. Using this data, CINCH developed a plan focused on education and communication, support for at-risk families, increased access to immunizations, and improved immunization delivery. After federal funding ended in 1995, members voted to expand the scope of the coalition to address additional child health needs and to broaden the membership. CINCH is a model for a sustainable city-citizen learning environment that intervenes to "help families help themselves to better health." The coalition is presented as an organization that focuses on community empowerment and development. The stages of coalition development and implications for coalition implementation in other sites are discussed.

Differential regulation of GABA(A) receptor gene expression by ethanol in the rat hippocampus versus cerebral cortex

Previous research has shown that chronic ethanol consumption dramatically alters GABA(A) receptor alpha1 and alpha4 subunit gene expression in the cerebral cortex and GABA(A) receptor alpha1 and alpha6 subunit gene expression in the cerebellum. However, it is not yet known if chronic ethanol consumption produces similar alterations in GABA(A) receptor gene expression in other brain regions. One brain region of interest is the hippocampus because it has recently been shown that a subset of GABA(A) receptors in the hippocampus is responsive to pharmacologically relevant concentrations of ethanol. Therefore, we directly compared the effects of chronic ethanol consumption on GABA(A) receptor subunit gene expression in the hippocampus and cerebral cortex. Furthermore, we investigated whether the duration of ethanol consumption (14 or 40 days) would influence regulation of GABA(A) receptor gene expression in these two brain regions. Chronic ethanol consumption produced a significant increase in the level of GABA(A) receptor alpha4 subunit peptide in the hippocampus following 40 days but not 14 days. The relative expression of hippocampal GABA(A) receptor alpha1, alpha2, alpha3, beta(2/3), or gamma2 was not altered by either period of chronic ethanol exposure. In marked contrast, chronic ethanol consumption for 40 days significantly increased the relative expression of cerebral cortical GABA(A) receptor alpha4 subunits and significantly decreased the relative expression of cerebral cortical GABA(A) receptor alpha1 subunits. This finding is consistent with previous results following 14 days of chronic ethanol consumption. Hence, chronic ethanol consumption alters GABA(A) receptor gene expression in the hippocampus but in a different manner from that in either the cerebral cortex or the cerebellum. Furthermore, these alterations are dependent on the duration of ethanol exposure.

A population-based study of access to immunization among urban Virginia children served by public, private, and military health care systems

BACKGROUND

Pediatric immunization rates have increased in the United States since 1990. Nevertheless, national survey data indicate that up to one third of 2-year-old children in some states and urban areas lack at least one recommended dose of diphtheria-tetanus-pertussis (DTP)-, polio-, or measles-containing vaccines. Immunization has become a key measure of preventive pediatric health care in the United States. To achieve and maintain the national immunization goal that 90% of children receive all recommended immunizations by 2 years of age, the role of the health care system in immunization delivery must be examined. Urban eastern Virginia has a diverse population that obtains immunization services from public, private, and military providers and insurers. At the time of this survey, immunization services in Virginia were available free to all children through public health clinics and to military families when using a military facility.

OBJECTIVE

To examine access to pediatric immunization services and health system factors associated with underimmunization in a representative sample of children at 12 and 24 months of age.

METHODS

We conducted a household survey in urban eastern Virginia from April through September 1993. A total of 12 770 households in Norfolk and Newport News, VA, were selected for inclusion in the study using probability-proportionate-to-size cluster sampling. Use of probability-proportionate-to-size sampling ensured that children within each city had equal probability of being included in the survey. Selected households were visited by trained interviewers to determine their eligibility, defined as having at least one child 12 to 30 months of age residing in the household. In eligible households, parents were asked to participate in a standardized, 15-minute interview. Survey respondents were asked about household demographics, and for each eligible child, the immunization history, health insurance, the name and location of all immunization providers, the usual immunization provider, and any problems the parent had experienced accessing immunization services with that child. Up-to-date (UTD) immunization status was defined as having all recommended doses of DTP, polio, and measles-mumps-rubella at 12 months (three DTP and two polio immunizations) and 24 months (four DTP, three polio, and one measles-mumps-rubella immunizations). The child's immunization history was assessed from parent and provider records only. Data analysis accounted for the survey's cluster sampling design (ie, within-cluster correlation). Because the immunization rates of the two cities did not differ significantly, unweighted analyses were used for ease of computation. Significance was determined for contingency tables by Wald's chi2 test.

RESULTS

A total of 749 children (91% of eligible households) participated in the survey. Study children were born between October, 1990, and July, 1992. Immunization records were obtained for 705 children (94%). Eighty-seven percent of respondents were mothers, 44% were African-American, 40% of children were military dependents, and 40% were enrolled in the Women, Infants and Children (WIC) program. Sixty-five percent of children were UTD at 12 months and 53% at 24 months. Parents reported that their children's usual immunization providers were private doctors (34%); public health, hospital clinics, or community health centers (32%); and military clinics or a military contract provider (34%). At least one problem accessing immunization services was reported by 35% of respondents, ranging from 29% among those who used a private doctor as their child's usual immunization provider to 46% among those using a military contract provider. Overall, the most commonly reported problem was clinic waiting time (12%), with reports of waiting time as a problem occurring most often among those using the military contract provider (22%) and public health clinics (17%). (ABSTRACT TRUNCATED)

Action of zolpidem on responses to GABA in relation to mRNAs for GABA(A) receptor alpha subunits within single cells: evidence for multiple functional GABA(A) isoreceptors on individual neurons

The relationship between zolpidem sensitivity and GABA(A) receptor alpha subunits was studied in individual dissociated neurons from rat brain. Using whole-cell recording, similar EC50 values were demonstrated for the effect of gamma-aminobutyric acid (GABA) on gated-chloride currents from substantia nigra reticulata (SNR) and lateral septal neurons. Subsequently, many neurons from both the SNR or lateral septum were found to exhibit enhanced GABA-gated chloride currents across concentrations of zolpidem ranging from 10 to 300 nM. Some neurons exhibited a greater than 20% increase in responsiveness to GABA at 30 nM of zolpidem without further increase at higher concentrations of zolpidem. Conversely, zolpidem enhancement of GABA from another group of neurons was not observed at 30 nM zolpidem, but between 100 and 300 nM the response to GABA increased greater than 20%. Finally, a third group of neurons reached both of these criteria for zolpidem enhancement of GABA. This latter spectrum of responses to GABA after varying concentrations of zolpidem was consistent with the presence of either two GABA(A) receptors or a single receptor with differing affinities for zolpidem on an individual neuron. Following determination of the sensitivity of neurons from SNR or lateral septum to zolpidem, cytoplasm was extracted from some individual cells to allow identification of cellular mRNAs for the alpha1, alpha2 and alpha3 GABA(A) receptor subunits with RT-PCR. Those neurons that responded to the 30 nM zolpidem concentration invariably expressed the alpha1-GABA(A) receptor subunit. This result is consistent with the GABA(A) alpha1-receptor subunit being an integral part of a functional high-affinity zolpidem type 1-BZD receptor complex on neurons in brain. Those neurons which showed enhancement of GABA from 100 to 300 nM zolpidem contained mRNAs for the alpha2 and/or the alpha3 receptor subunits, a finding consistent with these alpha subunits forming type 2-BZD receptors. Some individual dissociated SNR neurons were sensitive to both low and high concentrations of zolpidem and contained mRNAs for all three alpha-receptor subunits. These latter individual neurons are proposed to have at least two functional GABA(A) receptor subtypes. Thus, the present investigation emphasizes the importance of characterizing the relationship between endogenous GABA(A) receptor function and the presence of specific structural components forming GABA(A) receptor subtypes on neurons.

Regulation of GABA(A) receptor subunit mRNA expression by the pesticide dieldrin in embryonic brainstem cultures: a quantitative, competitive reverse transcription-polymerase chain reaction study

Cyclodiene organochlorine pesticides, such as dieldrin, inhibit gamma-aminobutyric acid (GABA)ergic neurotransmission by blocking the Cl- channel of GABA(A) receptors. This action may make the developing nervous system especially vulnerable to these neurotoxins, which could interfere with the trophic actions of GABA on developing neurons and alter expression of GABA(A) receptors. We have used an in vitro model to determine whether exposure to dieldrin alters developmental expression of GABA(A) receptor subunit mRNA transcripts. Dissociated cell cultures were prepared from embryonic day 14 (E14) brainstem and cultured in serum-containing medium for 1 day in vitro (DIV), then treated for 2 DIV with 10 microM dieldrin in serum-free medium. This dose was based on preliminary experiments and previous studies (Nagata et al.: Brain Res 645:19-26, 1994; Pomes et al.: J Pharmacol Exp Ther 271:1616-1623, 1994). Absolute amounts of alpha1, beta3, gamma1, gamma2S and gamma2L mRNA transcripts were quantified in these cultures by quantitative, competitive reverse transcription-polymerase chain reaction (RT-PCR) using subunit-selective internal standards. The most abundant GABA(A) subunit transcript was beta3, which was much more highly expressed than gamma2S, gamma1, gamma2L, or alpha1 subunit mRNAs. Dieldrin differentially regulated expression of these transcripts. Levels of beta3 subunit transcripts were significantly increased (by 300%) by dieldrin, whereas expression of gamma2S and gamma2L transcripts were decreased (by 50% and 40%, respectively). However, dieldrin did not alter the ratio of gamma2S to gamma2L transcripts, indicating that it did not affect alternative splicing of gamma2 transcripts. Dieldrin appeared to increase expression of alpha1 subunit transcripts, but this effect was not statistically significant. Dieldrin did not significantly alter expression of gamma1 subunit transcripts. These results support the hypothesis that in utero exposure to cyclodiene pesticides could pose a risk to the developing brain by virtue of their ability to alter gene expression of GABA(A) receptor subunits, which could produce GABA(A) receptors with altered functional properties.

Focus groups among public, military, and private sector mothers: insights to improve the immunization process

The underimmunization of children younger than 2 years old is a major health problem in U.S. cities. Innovative methods to increase immunization rates are being researched and implemented. In 1993, six focus groups were conducted with 41 mothers (25 African Americans and 16 Caucasians) to discuss their views regarding immunizations and the services they received from health care providers in the public health (n = 27), military (n = 4), and private (n = 10) sectors. Participants viewed immunizations positively, but perceived many barriers to immunization. They suggested the following ways to improve the immunization process: enhancing knowledge acquisition, improving reminder and appointment systems, providing transportation and child care, decreasing waiting times, improving the clinic environment, and making the immunizations less traumatic. According to mothers in this study, obtaining an immunization on time is a complex task that requires planning and resources. The fewer resources that are available to mothers, the more difficult it is to succeeded. Health care providers must help mothers identify and remove barriers if immunization rates are to be increased.

Bidirectional alterations of GABA(A) receptor subunit peptide levels in rat cortex during chronic ethanol consumption and withdrawal

The pharmacological properties of gamma-aminobutyric acidA (GABA(A)) receptors are altered by prolonged exposure to ethanol both in vivo and in vitro. We have shown previously that prolonged ethanol exposure elicits selective alterations in various GABA(A) receptor subunit mRNA levels in rat cerebral cortex. Some of these effects are rapidly reversed during ethanol withdrawal. The present study was conducted to determine the effects of prolonged ethanol exposure (dependence) and ethanol withdrawal on cerebral cortical peptide expression for several subunits. GABA(A) receptor alpha1 subunit peptide levels were decreased by nearly 40%, whereas alpha4 subunit peptide levels were increased by 27% in both ethanol-dependent and withdrawn rats. These changes correlate well with observed alterations in mRNA levels following prolonged ethanol exposure in dependent rats, but do not match the effects on mRNA levels during ethanol withdrawal. Beta2/3 subunit peptide levels increased by approximately 32% in both ethanol-dependent rats and rats undergoing ethanol withdrawal. We observed a 30-60% increase in gamma1 subunit peptide levels in both dependent rats and those undergoing withdrawal, also correlating with the previous report on ethanol-induced alterations in mRNA levels. Peptide levels for gamma2 subunits did not differ from control values in either condition. These findings show that specific alterations in GABA(A) receptor subunit peptide levels are associated with ethanol dependence in rats. GABA(A) receptor subunit peptide expression is more stable than mRNA expression, and mRNA levels are not representative of peptide expression during ethanol withdrawal. These findings are consistent with the suggestion that alterations in GABA(A) receptor gene expression underlie the functional properties of GABA(A) receptors in ethanol-dependent rats and those undergoing ethanol withdrawal.

The purpose and functions of immunization information systems within health care organizations

Abroad coalition of public and private health care organizations advocate the development of computerized immunization information systems as a key national strategy for achieving and sustaining high immunization coverage levels. However, widespread adoption requires greater awareness of the purpose, functions, and value of an immunization information system within health care organizations. We propose that the purpose of an immunization information system is to increase the efficiency and effectiveness of immunization-related practices and identify 9 potential functions that accomplish this purpose through improving patient care and practice management. When implementing an immunization information system within a practice setting, health care providers must consider technological and organizational issues. Health care providers should also look beyond their particular practice setting and establish public-private partnerships to create a system that links immunization data from all health care providers.

Adeno-associated virus (AAV) vector antisense gene transfer in vivo decreases GABA(A) alpha1 containing receptors and increases inferior collicular seizure sensitivity

In the inferior colliculus, adeno-associated virus (AAV) vectors are capable of gene transfer and stable, long-term expression, but it remained to be shown if this in vivo gene transfer could alter focal seizure sensitivity in the inferior colliculus. Because GABA receptors directly modulate inferior collicular seizures, AAV vectors were constructed with a cytomegalovirus (CMV) promoter and a truncated, human GABA(A) alpha1 cDNA in both the sense and antisense orientations. Seven days after collicular microinjection of the sense vectors (1 microl; 3 x 10(9) particles/microl), neurons exhibited GABA(A) alpha-like immunoreactivity in amounts far exceeding endogenous concentrations. Unilateral or bilateral sense vector infusion had no effect on inferior collicular seizure parameters or on [3H]zolpidem binding. In contrast, bilateral infusion of the antisense AAV-GABA(A) alpha1 vector (1 microl; 3 x 10(8) particles/microl) caused a 137% increase in the seizure duration. Moreover, unilateral antisense vector infusion produced a localized, 48% decrease in [3H]zolpidem binding. Thus, in the inferior colliculus, antisense AAV-CMV vectors can reduce a specific receptor subunit protein and change receptor function that directly influences in vivo seizure sensitivity.

GABAA receptors mediate trophic effects of GABA on embryonic brainstem monoamine neurons in vitro

The inhibitory neurotransmitter GABA may act as a trophic signal for developing monoamine neurons in embryonic rat brain, because GABA neurons and their receptors appear in brainstem during generation of monoamine neurons. To test this hypothesis, we used dissociated cell cultures from embryonic day 14 rat brainstem, which contains developing serotonin (5-HT), noradrenaline (tyrosine hydroxylase; TH), and GABA neurons. Immunocytochemistry and reverse transcription-PCR (RT-PCR) revealed the presence of multiple alpha, beta, gamma, and delta subunits in these cultures. Competitive RT-PCR demonstrated high levels of beta3 subunit transcripts. Expression of functional GABAA receptors was demonstrated using 36Cl- flux assays. To investigate GABAergic regulation of neuronal survival and growth, cultures were treated for 1-3 d in vitro with 10 microM GABA and/or GABAA antagonist (bicuculline or the pesticide dieldrin). The effects of treatments were quantified by analysis of immunoreactive 5-HT, TH, and GABA neurons. GABAA receptor ligands differentially regulated neuronal survival and growth depending on neurotransmitter phenotype. GABA exerted positive effects on monoamine neurons, which were countered by bicuculline (and dieldrin, 5-HT neurons only). By itself, bicuculline produced inhibitory effects on both 5-HT and TH neurons, whereas dieldrin potently inhibited 5-HT neurons only. GABA neurons responded positively to both antagonists, but more strongly to bicuculline. Taken together, these results demonstrate that the activation/inhibition of GABAA receptors produces opposite effects on the development of embryonic monoamine and GABA neurons. This suggests that these neurotransmitter phenotypes may express GABAA receptors that differ in fundamental ways, and these differences determine the developmental responses of these cells to GABAergic stimuli.