Tryptophan Hydroxylase 2 Knockout Male Rats Exhibit a Strengthened Oxytocin System, Are Aggressive, and Are Less Anxious

The central serotoninergic system is critical for stress responsivity and social behavior, and its dysregulations have been centrally implicated in virtually all neuropsychiatric disorders. Genetic serotonin depletion animal models could provide a tool to elucidate the causes and mechanisms of diseases and to develop new treatment approaches. Previously, mice lacking tryptophan hydroxylase 2 (Tph2) have been developed, showing altered behaviors and neurotransmission. However, the effect of congenital serotonin deficiency on emotional and social behavior in rats is still largely unknown, as are the underlying mechanisms. In this study, we used a Tph2 knockout (Tph2^-/-) male rat model to study how the lack of serotonin in the rat brain affects anxiety-like and social behaviors. Since oxytocin is centrally implicated in these behaviors, we furthermore explored whether the effects of Tph2 knockout on behavior would relate to changes in the oxytocin system. We show that Tph2^-/- rats display reduced anxiety-like behavior and a high level of aggression in social interactions. In addition, oxytocin receptor expression was increased in the infralimbic and prelimbic cortices, paraventricular nucleus, dorsal raphe nucleus, and some subregions of the hippocampus, which was paralleled by increased levels of oxytocin in the medial frontal cortex and paraventricular nucleus but not the dorsal raphe nucleus, central amygdala, and hippocampus. In conclusion, our study demonstrated reduced anxiety but exaggerated aggression in Tph2^-/- male rats and reveals for the first time a potential involvement of altered oxytocin system function. Meanwhile, the research of oxytocin could be distinguished in almost any psychiatric disorder including anxiety and mental disorders. This research potentially proposes a new target for the treatment of such disorders, from a genetic serotonin deficiency aspect.

Chemical Modifications of Gold Surfaces with Basic Groups and a Fluorescent Nanoparticle Adhesion Assay To Determine Their Surface p Ka

For pharmaceutical, biological, and biomedical applications, the functionalization of gold surfaces with pH-sensitive groups has great potential. The aim of this work was to modify gold surfaces with pH-sensitive groups and to determine the p K_a of the modified gold surfaces using a fluorescent nanoparticle adhesion assay. To introduce pH-sensitive groups onto gold surfaces, we modified gold-coated silicon slides with four different bases: 4-mercaptopyridine (4-MP), 4-pyridylethylmercaptan (4-PEM), 4-aminothiophenol (4-ATP), and 2-mercaptoethylamine (2-MEA). To screen whether the modifications were successful, the binding of negatively charged fluorescently labeled nanoparticles to the positively charged surfaces was visualized by fluorescence microscopy and atomic force microscopy. Next, the p K_a of the modified surfaces was determined by quantifying the pH-dependent adhesion of the fluorescently labeled nanoparticles with fluorescence spectroscopy. Fluorescence microscopy showed that the gold surfaces were successfully modified with the four different basic molecules. Moreover, fluorescence spectroscopy revealed that fluorescently labeled negatively charged nanoparticles bound onto gold surfaces that were modified with one of the four bases in a pH-dependent manner. By quantifying the adsorption of negatively charged fluorescently labeled nanoparticles onto the functionalized gold surfaces and using the Henderson-Hasselbalch equation, the p K_a of these surfaces was determined to be 3.7 ± 0.1 (4-MP), 5.0 ± 0.1 (4-PEM), 5.4 ± 0.1 (4-ATP), and 7.4 ± 0.3 (2-MEA). We successfully functionalized gold surfaces with four different basic molecules, yielding modified surfaces with different p K_a values, as determined with a fluorescent nanoparticle adhesion assay.

Impaired Fear Extinction Recall in Serotonin Transporter Knockout Rats Is Transiently Alleviated during Adolescence

Adolescence is a developmental phase characterized by emotional turmoil and coincides with the emergence of affective disorders. Inherited serotonin transporter (5-HTT) downregulation in humans increases sensitivity to these disorders. To reveal whether and how 5-HTT gene variance affects fear-driven behavior in adolescence, we tested wildtype and serotonin transporter knockout (5-HTT^-/-) rats of preadolescent, adolescent, and adult age for cued fear extinction and extinction recall. To analyze neural circuit function, we quantified inhibitory synaptic contacts and, through RT-PCR, the expression of c-Fos, brain-derived neurotrophic factor (BDNF), and NDMA receptor subunits, in the medial prefrontal cortex (mPFC) and amygdala. Remarkably, the impaired recall of conditioned fear that characterizes preadolescent and adult 5-HTT^-/- rats was transiently normalized during adolescence. This did not relate to altered inhibitory neurotransmission, since mPFC inhibitory immunoreactivity was reduced in 5-HTT^-/- rats across all ages and unaffected in the amygdala. Rather, since mPFC (but not amygdala) c-Fos expression and NMDA receptor subunit 1 expression were reduced in 5-HTT^-/- rats during adolescence, and since PFC c-Fos correlated negatively with fear extinction recall, the temporary normalization of fear extinction during adolescence could relate to altered plasticity in the developing mPFC.

Acute inescapable stress alleviates fear extinction recall deficits caused by serotonin transporter abolishment

Life stress increases risk for developing post-traumatic stress disorder (PTSD), and more prominently so in short-allele carriers of the serotonin transporter linked polymorphic region (5-HTTLPR). Serotonin transporter knockout (5-HTT^-/-) rats show compromised extinction (recall) of conditioned fear, which might mediate the increased risk for PTSD and reduce the therapeutic efficacy of exposure therapy. Here, we assessed whether acute inescapable stress (IS) differentially affects fear extinction and extinction recall in 5-HTT^-/- rats and wildtype controls. Surprisingly, IS experience improved fear extinction recall in 5-HTT^-/- rats to the level of wildtype animals, while wildtypes were unaffected by this IS. Thus, whereas 5-HTT^-/- rats evidently were more responsive to the stressor, the behavioral consequences presented themselves as adaptive.

Prior fear conditioning does not impede enhanced active avoidance in serotonin transporter knockout rats

Stressors can be actively or passively coped with, and adequate adaption of the coping response to environmental conditions can reduce their potential deleterious effects. One major factor influencing stress coping behaviour is serotonin transporter (5-HTT) availability. Abolishment of 5-HTT is known to impair fear extinction but facilitates acquisition of signalled active avoidance (AA), a behavioural task in which an animal learns to avoid an aversive stimulus that is predicted by a cue. Flexibility in adapting coping behaviour to the nature of the stressor shapes resilience to stress-related disorders. Therefore, we investigated the relation between 5-HTT expression and ability to adapt a learned coping response to changing environmental conditions. To this end, we first established and consolidated a cue-conditioned passive fear response in 5-HTT^-/- and wildtype rats. Next, we used the conditioned stimulus (CS) to signal oncoming shocks during signalled AA training in 5-HTT^-/- and wildtype rats to study their capability to acquire an active coping response to the CS following fear conditioning. Finally, we investigated the behavioural response to the CS in a novel environment and measured freezing, exploration and self-grooming, behaviours reflective of stress coping strategy. We found that fear conditioned and sham conditioned 5-HTT^-/- animals acquired the signalled AA response faster than wildtypes, while prior conditioning briefly delayed AA learning similarly in both genotypes. Subsequent exposure to the CS in the novel context reduced freezing and increased locomotion in 5-HTT^-/- compared to wildtype rats. This indicates that improved AA performance in 5-HTT^-/- rats resulted in a weaker residual passive fear response to the CS in a novel context. Fear conditioning prior to AA training did not affect freezing upon re-encountering the CS, although it did reduce locomotion in 5-HTT^-/- rats. We conclude that independent of 5-HTT signalling, prior fear conditioning does not greatly impair the acquisition of subsequent active coping behaviour when the situation allows for it. Abolishment of 5-HTT results in a more active coping style in case of novelty-induced fear and upon CS encounter in a novel context after AA learning.

[Combining a classic monoamine oxidase inhibitor with a tricyclic antidepressant in therapy-resistant depression: a case report and literature review]

Combining a monoamine oxidase inhibitor (MAOI) with a tricyclic antidepressant (TCA) is considered to be contra-indicated because there is a risk that the recipient develops a serotonin syndrome. An accidental clinical observation motivated us to search and study publications relating to the risk and effectivity of combining these two types of antidepressants.<br/> AIM: To search and study articles on the risks and effectivity of combining the use of MAOIs and TCAs in the treatment of therapy-resistant depression.<br/> METHOD: We searched in PubMed and also studied relevant articles that papers referred to in the database.<br/> RESULTS: Because many case-reports have been misinterpreted, the patients' risk of developing a serotonin syndrome and other complications as a result of the combined use of MAOIs and TCAs is overestimated. The literature provides some evidence that the combination therapy may be effective for some patients who have not responded to TCA or MAO-I monotherapy. Combination therapy seems to be safe if monitored carefully and if TCAs with marked serotonergic affinity are avoided. To enhance safety, the MAOI should be added to a TCA or both the TCA and MAOI should be started simultaneously and titrated slowly.<br/> CONCLUSION: The combination of a MAOI and a TCA can be a possible treatment for patients with treatment resistant depression when monotherapy with either a TCA or a MAOI has failed.

Improved Stress Control in Serotonin Transporter Knockout Rats: Involvement of the Prefrontal Cortex and Dorsal Raphe Nucleus

Variations in serotonin transporter (5-HTT) expression have been associated with altered sensitivity to stress. Since controllability is known to alter the impact of a stressor through differential activation of the medial prefrontal cortex (mPFC) and dorsal raphe nucleus (DRN), and that these regions are functionally affected by genetic 5-HTT down-regulation, we hypothesized that 5-HTT expression modulates the effect of controllability on stressor impact and coping. Here, we investigated the effects of a signaled stress controllability task or a yoked uncontrollable stressor on behavioral responding and mPFC and DRN activation. 5-HTT(-/-) rats proved better capable of acquiring the active avoidance task than 5-HTT(+/+) animals. Controllability determined DRN activation in 5-HTT(+/+), but not 5-HTT(-/-), rats, whereas controllability-related activation of the mPFC was independent of genotype. These findings suggest that serotonergic activation in the DRN is involved in stress coping in a 5-HTT expression dependent manner, whereas mPFC activation seems to be implicated in control over stress independently of 5-HTT expression. We speculate that alterations in serotonergic feedback in the DRN might be a potential mechanism driving this differential stress coping.

Impaired fear extinction as displayed by serotonin transporter knockout rats housed in open cages is disrupted by IVC cage housing

Anxiety disorders are influenced by both environmental and genetic factors. A well-known example for gene x environment interactions in psychiatry is the low activity (s) allelic variant of the serotonin transporter (5-HTT) promoter polymorphism (5-HTTLPR) that in the context of stress increases risk for depression and post-traumatic stress disorder (PTSD). Previously, we observed robust anxiety-related phenotypes, such as an impairment in fear extinction, in 5-HTT knockout (5-HTT^−/−) versus wild-type (5-HTT^+/+) rats housed in open cages. Recently, housing conditions were changed from open cages to individually ventilated cages (IVC), which are associated with a high ventilation fold and noise. This switch in housing conditions prompted an unplanned 5-HTT gene x environment interaction study in our rats. The current study shows that lifetime stress by means of IVC cage housing abolished genotype differences in fear extinction between 5-HTT^−/− and 5-HTT^+/+ rats. Although this effect was not attributed specifically to either the 5-HTT^+/+ or the 5-HTT^−/− genotype, the findings are in agreement with the modulatory role of serotonin in the processing of environmental stimuli. Our findings also underline the possibility that housing conditions confound the interpretation of anxiety-related behaviours in rodents.

Long-term oral methylphenidate treatment in adolescent and adult rats: differential effects on brain morphology and function

Methylphenidate is a widely prescribed psychostimulant for treatment of attention deficit hyperactivity disorder (ADHD) in children and adolescents, which raises questions regarding its potential interference with the developing brain. In the present study, we investigated effects of 3 weeks oral methylphenidate (5 mg/kg) vs vehicle treatment on brain structure and function in adolescent (post-natal day [P]25) and adult (P65) rats. Following a 1-week washout period, we used multimodal magnetic resonance imaging (MRI) to assess effects of age and treatment on independent component analysis-based functional connectivity (resting-state functional MRI), D-amphetamine-induced neural activation responses (pharmacological MRI), gray and white matter tissue volumes and cortical thickness (postmortem structural MRI), and white matter structural integrity (postmortem diffusion tensor imaging (DTI)). Many age-related differences were found, including cortical thinning, white matter development, larger dopamine-mediated activation responses and increased striatal functional connectivity. Methylphenidate reduced anterior cingulate cortical network strength in both adolescents and adults. In contrast to clinical observations from ADHD patient studies, methylphenidate did not increase white matter tissue volume or cortical thickness in rat. Nevertheless, DTI-based fractional anisotropy was higher in the anterior part of the corpus callosum following adolescent treatment. Furthermore, methylphenidate differentially affected adolescents and adults as evidenced by reduced striatal volume and myelination upon adolescent treatment, although we did not observe adverse treatment effects on striatal functional activity. Our findings of small but significant age-dependent effects of psychostimulant treatment in the striatum of healthy rats highlights the importance of further research in children and adolescents that are exposed to methylphenidate.

Serotonin transporter genotype x construction stress interaction in rats

A well-known example for gene x environment interactions in psychiatry is the one involving the low activity (s) allelic variant of the serotonin transporter (5-HTT) promoter polymorphism (5-HTTLPR) that in the context of stress increases risk for depression. In analogy, 5-HTT knockout rodents are highly responsive to early life, but also adult external stressors, albeit conflicting data have been obtained. In our study on emotion and cognition using homozygous 5-HTT knockout (5-HTT(-/-)) and wild-type (5-HTT(+/+)) rats we have been confronted with animal facility construction, which were associated with severe lifetime stress (noise and vibrations). To assess the impact of construction stress on well-established 5-HTT(-/-) rat phenotypes we conducted ad hoc analyses of 5-HTT(-/-) and 5-HTT(+/+) rats that grew up before and during the construction. The reproductive capacity of the parents of the experimental 5-HTT(+/-) rats was significantly decreased. Further, 5-HTT(-/-) anxiety-related phenotypes in the elevated plus maze and social interaction tests were abolished after construction noise exposure, due to increased anxiety in 5-HTT(+/+) rats and decreased anxiety in 5-HTT(-/-) rats (social interaction test only). In addition, reversal learning was improved in 5-HTT(+/+) and, to a milder extent, decreased in 5-HTT(-/-) rats. Finally, construction stress genotype-independently increased behavioural despair in the forced swim test. In conclusion, severe construction stress induces 5-HTT genotype-dependent 'for-better-and-for-worse' effects. These data importantly contribute to the understanding of 5-HTT gene x environment interactions and show the risk of losing genotype effects by construction stress.

Fluoxetine exerts age-dependent effects on behavior and amygdala neuroplasticity in the rat

The selective serotonin reuptake inhibitor (SSRI) Prozac® (fluoxetine) is the only registered antidepressant to treat depression in children and adolescents. Yet, while the safety of SSRIs has been well established in adults, serotonin exerts neurotrophic actions in the developing brain and thereby may have harmful effects in adolescents. Here we treated adolescent and adult rats chronically with fluoxetine (12 mg/kg) at postnatal day (PND) 25 to 46 and from PND 67 to 88, respectively, and tested the animals 7–14 days after the last injection when (nor)fluoxetine in blood plasma had been washed out, as determined by HPLC. Plasma (nor)fluoxetine levels were also measured 5 hrs after the last fluoxetine injection, and matched clinical levels. Adolescent rats displayed increased behavioral despair in the forced swim test, which was not seen in adult fluoxetine treated rats. In addition, beneficial effects of fluoxetine on wakefulness as measured by electroencephalography in adults was not seen in adolescent rats, and age-dependent effects on the acoustic startle response and prepulse inhibition were observed. On the other hand, adolescent rats showed resilience to the anorexic effects of fluoxetine. Exploratory behavior in the open field test was not affected by fluoxetine treatment, but anxiety levels in the elevated plus maze test were increased in both adolescent and adult fluoxetine treated rats. Finally, in the amygdala, but not the dorsal raphe nucleus and medial prefrontal cortex, the number of PSA-NCAM (marker for synaptic remodeling) immunoreactive neurons was increased in adolescent rats, and decreased in adult rats, as a consequence of chronic fluoxetine treatment. No fluoxetine-induced changes in 5-HT_1A receptor immunoreactivity were observed. In conclusion, we show that fluoxetine exerts both harmful and beneficial age-dependent effects on depressive behavior, body weight and wakefulness, which may relate, in part, to differential fluoxetine-induced neuroplasticity in the amygdala.

Increased polysialic acid neural cell adhesion molecule expression in human hippocampus of heroin addicts

Chronic exposure to heroin is known to cause cognitive deficits. However, little is known about the underlying molecular mechanisms. It has been suggested that opiate-induced neurotoxicity as well as impaired plasticity and regeneration may be relevant. One of the target regions where regeneration still can be observed in the adult brain is the hippocampus. Since polysialic acid neural cell adhesion molecule is regarded as one of the key players involved in plasticity and regeneration of neural tissue, we analyzed polysialic acid neural cell adhesion molecule expression in the fascia dentate hilus of the human hippocampus of 29 lethally intoxicated heroin addicts and matched controls. Immunohistochemistry with an antibody directed against polysialic acid neural cell adhesion molecule revealed its expression in differently sized cells which could be identified as neurons and glial cells. We observed an increase in the percentage of polysialic acid neural cell adhesion molecule positive neurons in hippocampal hilus of heroin addicts compared with controls (P = 0.001).Interestingly, we also observed polysialic acid neural cell adhesion molecule expression in glial cells as evidenced by double immunofluorescence with glial fibrillary acidic protein and polysialic acid neural cell adhesion molecule using confocal laser scanning microscopy. The fraction of polysialic acid neural cell adhesion molecule positive glial cells was also higher in heroin addicts compared with controls (P = 0.009). In addition, within the group of addicts morphine blood concentrations showed a positive correlation with the percentage of polysialic acid neural cell adhesion molecule positive neurons (P = 0.04; r = 0.547). In conclusion, we observed an increase in polysialic acid neural cell adhesion molecule positive neurons and glial cells in hippocampi of heroin addicts. This might reflect an attempt to repair cell damage due to heroin exposure.

Applicability of a real-time quantitative PCR assay for diagnosis of respiratory syncytial virus infection in immunocompromised adults

Respiratory syncytial virus (RSV) accounts for the majority of respiratory virus infections, producing high mortality rates in immunocompromised patients with hematologic malignancies. The available methods for the rapid detection of RSV by antigen detection or PCR either lack sensitivity, require complex laboratory manipulation, or have not been evaluated in this patient population. To assess the applicability of a TaqMan-based real-time PCR technique for the detection of RSV A and B in immunocompromised adults, we developed a rapid, sensitive detection method that simultaneously detects RSV A and B and can be applied in routine diagnostics. The specificity of the assay was assessed using a panel of reference strains of other respiratory viruses and RSV. Electron microscopy-counted stocks of RSV A and B were used to develop a quantitative PCR format. Eleven copies of viral RNA could be detected for RSV A strain Long, and 14 copies could be detected for RSV B strain 9320, corresponding to 50% tissue culture infective doses of 0.86 and 0.34, respectively. The assay was evaluated on 411 combined nose and throat swabs derived from immunocompromised adults with or without signs of respiratory tract infection. The diagnostic efficacy of the TaqMan PCR determined on the clinical samples showed that this real-time PCR technique was substantially more sensitive than the combination of conventional viral culture and shell vial culture. None of the clinical specimens derived from patients without signs of respiratory illness were found to be positive for RSV by real-time TaqMan PCR.

Clinical diagnosis of influenza virus infection: evaluation of diagnostic tools in general practice

BACKGROUND

With the development of new antiviral agents for influenza, the urge for rapid and reliable diagnosis of influenza becomes increasingly important. Respiratory virus infections are difficult to distinguish on clinical grounds. General practitioners (GPs) however, still depend on their clinical judgement.

AIM

To evaluate the importance of clinical symptoms in the diagnosis of influenza virus infection.

DESIGN OF STUDY

A multicentre questionnaire study.

SETTING

Eighty-one patients from 14 general practices.

METHOD

Patients with fever and at least one constitutional symptom and one respiratory symptom were included. A questionnaire with the medical history and clinical symptoms was completed and a combined nose-throat swab was taken. Virus culture, rapid culture, and polymerase chain reaction (PCR) amplification were performed on each specimen. Multivariate analysis was used to obtain the best predictive model.

RESULTS

By using PCR, an increase was seen in the detection of the viral pathogens compared with the results of culture. In 42 out of 81 patients PCR was positive for influenza. A positive predictive value (PPV) of 75% was observed for the combination of headache at onset, feverishness at onset, cough, and vaccination status during the period of increase influenza activity. Criteria used by the ICHPPC-2 resulted in a PPV of 54%. The PPV for diagnosis made by the GP was 76%.

CONCLUSION

Although influenza is difficult to diagnose on clinical grounds, the GPs in this study were able to diagnose influenza as such more accurately on their judgement than by the other criteria.

Simultaneous detection of influenza viruses A and B using real-time quantitative PCR

Since influenza viruses can cause severe illness, timely diagnosis is important for an adequate intervention. The available rapid detection methods either lack sensitivity or require complex laboratory manipulation. This study describes a rapid, sensitive detection method that can be easily applied to routine diagnosis. This method simultaneously detects influenza viruses A and B in specimens of patients with respiratory infections using a TaqMan-based real-time PCR assay. Primers and probes were selected from highly conserved regions of the matrix protein gene of influenza virus A and the hemagglutinin gene segment of influenza virus B. The applicability of this multiplex PCR was evaluated with 27 influenza virus A and 9 influenza virus B reference strains and isolates. In addition, the specificity of the assay was assessed using eight reference strains of other respiratory viruses (parainfluenza viruses 1 to 3, respiratory syncytial virus Long strain, rhinoviruses 1A and 14, and coronaviruses OC43 and 229E) and 30 combined nose and throat swabs from asymptomatic subjects. Electron microscopy-counted stocks of influenza viruses A and B were used to develop a quantitative PCR format. Thirteen copies of viral RNA were detected for influenza virus A, and 11 copies were detected for influenza virus B, equaling 0.02 and 0.006 50% tissue culture infective doses, respectively. The diagnostic efficacy of the multiplex TaqMan-based PCR was determined by testing 98 clinical samples. This real-time PCR technique was found to be more sensitive than the combination of conventional viral culturing and shell vial culturing.

Increased fitness of drug resistant HIV-1 protease as a result of acquisition of compensatory mutations during suboptimal therapy

OBJECTIVE

It is thought as a consequence of continuous replication, HIV-1 has acquired an optimal fitness state and that suboptimal antiretroviral therapy selects for drug resistant variants which show impaired fitness in the absence of the drug. In this paper we studied the evolution and fitness of viral populations appearing in a patient who received protease monotherapy.

METHODS

Two factors contributing to fitness, drug resistance and protease catalytic activity, were studied at the enzymatic and virological level.

RESULTS

The first drug resistant viral variants that were selected in vivo harboured one to three protease substitutions. These mutants showed reduced protease activity and consequently a reduction in viral replication capacity. During continued in vivo replication of these viruses in the presence of the drug, novel variants harbouring additional substitutions in the viral protease appeared. These variants did not display any further increase in drug resistance but demonstrated clearly increased protease activity. Consequently the replication capacity of these viruses was raised to a level at which they replicated better than the original wild-type virus.

CONCLUSION

This study indicates that the viral population in the patient does not have to represent the fittest possible variants, and thus antiretroviral therapy may drive the viral population first through a lower fitness level and then to a higher fitness level.

Stochastic processes strongly influence HIV-1 evolution during suboptimal protease-inhibitor therapy

It has long been assumed that HIV-1 evolution is best described by deterministic evolutionary models because of the large population size. Recently, however, it was suggested that the effective population size (Ne) may be rather small, thereby allowing chance to influence evolution, a situation best described by a stochastic evolutionary model. To gain experimental evidence supporting one of the evolutionary models, we investigated whether the development of resistance to the protease inhibitor ritonavir affected the evolution of the env gene. Sequential serum samples from five patients treated with ritonavir were used for analysis of the protease gene and the V3 domain of the env gene. Multiple reverse transcription-PCR products were cloned, sequenced, and used to construct phylogenetic trees and to calculate the genetic variation and Ne. Genotypic resistance to ritonavir developed in all five patients, but each patient displayed a unique combination of mutations, indicating a stochastic element in the development of ritonavir resistance. Furthermore, development of resistance induced clear bottleneck effects in the env gene. The mean intrasample genetic variation, which ranged from 1.2% to 5.7% before treatment, decreased significantly (P < 0.025) during treatment. In agreement with these findings, Ne was estimated to be very small (500-15,000) compared with the total HIV-1 RNA copy number. This study combines three independent observations, strong population bottlenecking, small Ne, and selection of different combinations of protease-resistance mutations, all of which indicate that HIV-1 evolution is best described by a stochastic evolutionary model.

Human immunodeficiency virus type 1 drug susceptibility determination by using recombinant viruses generated from patient sera tested in a cell-killing assay

A simple approach for the determination of drug susceptibilities by using human immunodeficiency virus type 1 (HIV-1) RNA from the sera of patients is described. HIV-1 RNA was extracted from patient sera, and the 5' part of the reverse transcriptase (RT) gene was transcribed into DNA and amplified in a nested PCR. The amplified fragment covers the 3' part of the protease gene and amino acids 1 to 304 of the RT gene. This fragment can be introduced through homologous recombination, as described previously, into a novel HIV-1 reference strain (pHXB2 delta 2-261RT) from which amino acids 2 to 261 of RT have been deleted. The resulting recombinant virus expresses all properties of the HXB2 reference strain except for those encoded by the introduced part of the patient RT gene. Recombinant viruses were subsequently tested for drug susceptibility in a microtiter format killing assay [3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay] as well as in the standard HeLa CD4+ plaque reduction assay. Similar susceptibility profiles were obtained by each assay with recombinant viruses derived from patients receiving alternating nevirapine and zidovudine treatment or lamivudine-zidovudine combination therapy. In conclusion, this approach enables high-through-put determination of the drug susceptibilities of serum RNA-derived RT genes, independent of the patient's viral background, and generates the possibility of relating changes in susceptibility to changes in viral genotypes.

Rapid changes in human immunodeficiency virus type 1 RNA load and appearance of drug-resistant virus populations in persons treated with lamivudine (3TC)

The effect of the appearance of drug-resistant human immunodeficiency virus type 1 (HIV-1) on viral RNA load was studied in patients treated with the reverse transcriptase inhibitor lamivudine. During the first 12 weeks of treatment, HIV-1 RNA concentrations and amino acid changes in codon 184, causing high-level resistance to lamivudine, were determined in longitudinal serum samples from HIV-1 p24 antigen-positive and -negative patients. A marked decline in the amount of HIV-1 RNA (approximately 95% below baseline) and HIV-1 p24 antigen was observed within 2 weeks, followed by a rise that coincided with the appearance of lamivudine-resistant viruses in serum (isoleucine mutants initially, which were subsequently replaced by valine variants). After 12 weeks, a partial antiviral effect was observed despite the presence of a complete codon 184 mutant virus population in serum. This study shows that the rapid appearance of drug-resistant virus in serum is followed by an increase in viral RNA load.

Familial hypokalemia/hypomagnesemia and chondrocalcinosis

OBJECTIVE

Familial occurrence of Bartter's syndrome is well known, but the simultaneous occurrence of hypokalemia/hypomagnesemia and chondrocalcinosis in one family has not been described. We present the clinical, laboratory and radiological findings of a family, in which 7 members were affected by disease.

METHODS

A total of 43 members of the family could be interviewed concerning their general health, past diseases and joint complaints. Serum potassium and magnesium were determined in all and radiographic studies were performed in those who had hypokalemia and hypomagnesemia or those with merely articular complaints. Urinary excretion of potassium, magnesium and calcium were determined in the affected persons.

RESULTS

Seven patients were found with hypokalemia and hypomagnesemia. Urinary potassium and magnesium excretion was inappropriately high when compared to the serum levels of these electrolytes. All patients had hypocalciuria and extensive chondrocalcinosis, mainly in the knees, elbows and shoulders. In one patient, most probably as a result of magnesium supplementation, a striking reduction of chondrocalcinosis was observed during a followup of 10 years.

CONCLUSION

A family with familial hypokalemia/hypomagnesemia and chondrocalcinosis is described. The reduction of chondrocalcinosis, after years of magnesium supplementation in one patient, suggests that hypomagnesemia is an important factor in the pathogenesis of chondrocalcinosis in these patients.

Alternating nevirapine and zidovudine treatment of human immunodeficiency virus type 1-infected persons does not prolong nevirapine activity

The potential use of an alternating treatment strategy with nevirapine and zidovudine in prolonging the antiretroviral effects of nevirapine was evaluated. Ten human immunodeficiency virus type 1 (HIV-1)-infected p24 antigen-positive persons who had not received prior antiretroviral therapy were treated for 9-13 weeks with an alternating regimen of 1 week of nevirapine (200 mg/day) and 3 weeks of zidovudine (600 mg/day). Serum p24 antigen levels declined during the first week of nevirapine treatment (median, 59%); however, subsequent courses of nevirapine were characterized by rising p24 antigen levels, while antigen levels remained stable or declined during zidovudine treatment. Serum beta 2-microglobulin levels and CD4+ cell counts exhibited similar responses. HIV-1 isolates obtained from 2 patients revealed 40- and 1000-fold reductions in nevirapine sensitivity after 8 weeks. These findings demonstrate that alternating treatment with zidovudine and nevirapine does not prolong the effectiveness of nevirapine and does not prevent the development of nevirapine resistance.

High-level resistance to (-) enantiomeric 2'-deoxy-3'-thiacytidine in vitro is due to one amino acid substitution in the catalytic site of human immunodeficiency virus type 1 reverse transcriptase

Passage of human immunodeficiency virus type 1 in the presence of increasing 2'-deoxy-3'-thiacytidine (3TC) concentrations results in high-level (> 100-fold) 3TC-resistant viruses. All 3TC-resistant viruses possess a substitution at the second codon (from a methionine into an isoleucine) at position 184 within the highly conserved motif (YMDD) of human immunodeficiency virus type 1 reverse transcriptase. 3TC-resistant viruses were cross-resistant to the (-) enantiomer of the fluorinated derivative of BCH-189 but remained susceptible to 2',3'-dideoxyinosine and 2',3'-dideoxycytidine. The susceptibilities of the 3TC-resistant viruses to the (+) enantiomers of BCH-189 and the fluorinated derivative of BCH-189 demonstrate an enantiomeric specificity for viruses selected under these conditions. Introduction of an isoleucine substitution at codon 184 into a background of two known 3'-azido-3'-deoxythymidine resistance mutations (amino acids 41 and 215) restored the susceptibility of this virus to 3'-azido-3'-deoxythymidine.

Effects of discontinuation of zidovudine treatment on zidovudine sensitivity of human immunodeficiency virus type 1 isolates

Zidovudine treatment of individuals infected with human immunodeficiency virus type 1 (HIV-1) results in HIV-1 isolates with a reduced zidovudine sensitivity in vitro. This reduction is due to mutations causing amino acid substitutions at five codons (41, 67, 70, 215, and 219) on the reverse transcriptase enzyme of HIV. HIV-1 isolates were obtained 8 to 69 weeks after therapy discontinuation from 10 patients at different stages of disease. Zidovudine sensitivity was determined by the HeLa CD4+ plaque assay. The presence of the resistance-conferring mutations was determined by using a selective polymerase chain reaction. Sensitivity could be determined for six isolate pairs: one showed a decline in the 50% inhibitory zidovudine concentration after therapy discontinuation; four pairs did not show a change. The majority of changes in the five codons in isolates from all 10 patients were the result of a relative increase in the wild-type sequence. Complete changes from mutant to the wild type were seen for only two codons in isolates from two patients. This study of isolates from a small group of individuals at different stages of disease, who had been taking zidovudine for 1 to 2 years, shows that a period of 1 year without zidovudine may be required to achieve a change from a mutant or mixed virus population to a wild-type virus population.

Introduction of the human interleukin-6 (IL-6) receptor in murine IL-3-dependent hematopoietic cells restores responsiveness to IL-6

To create experimental systems that facilitate studies aimed at the responsiveness of hematopoietic progenitors to interleukin (IL)-6 in combination with IL-3, we introduced the human IL-6 receptor (hIL-6R) into the IL-3-dependent cell line 32D. For this purpose, a retroviral vector containing the hIL-6R cDNA was constructed. 32D parental cells did not respond to IL-6, neither alone nor in combination with increasing concentrations of IL-3, and did not express detectable numbers of IL-6R as determined by 125I-IL-6 binding. 32D/hIL-6R cells expressed high-affinity IL-6 binding and responded synergistically to IL-6 in combination with suboptimal amounts of IL-3 in DNA synthesis assays. In addition, IL-6 promoted the short-term survival of IL-3-responsive clonogenic 32D/hIL-6R cells. On the other hand, although introduction of hIL-6R resulted in the formation of high-affinity IL-6 receptor structures in the IL-2-dependent thymocyte cell line CTLL, CTLL/hIL-6R cells did not respond to IL-6 in synergy with IL-2. We conclude that 32D cells possess the intracellular machinery permissive for IL-6 signal transduction. Murine IL-3-dependent cell lines with ectopic IL-6 receptors can serve as models for dissecting the molecular basis of IL-6 responses in primitive hematopoietic cells.

Acute myeloid leukemias with chromosomal abnormalities involving the 21q22 region identified by their in vitro responsiveness to interleukin-5

Among 52 patients diagnosed as acute myeloid leukemia (AML), nine cases were found in which interleukin-5 (IL-5) induced a proliferative response in the leukemic cells, as measured by the stimulation of DNA synthesis or colony formation in vitro. All cases (n = 7) with the cytogenetic abnormality t(8;21)(q22;q22) belonged to this group of IL-5 responders. Of the additional two cases, one had an apparently normal karyotype, but the other expressed a dicentric chromosome 21, an abnormality also involving the breakpoint region 21q22. The leukemic cells of the IL-5 responsive patients could also be stimulated to proliferate by IL-3, GM-CSF and G-CSF, and in some cases by IL-6 or M-CSF. Immunophenotypic analysis revealed the presence of the immature hematopoietic cell antigen CD34, the myelomonocytic maturation antigens CD13 and CD33, in association with the B-cell related surface marker CD19 on the leukemic cells. Immunoglobulin mu and T-cell receptor beta-genes in the leukemic cells were in germline configuration. Upon incubation in colony culture, clonogenic cells were capable of producing progeny showing eosinophilic or neutrophilic maturation following stimulation with IL-5 or G-CSF, respectively. It is concluded that IL-5 responsive AML represents a subgroup of leukemia with distinct immunotypic and cytogenetic features.

Interleukin-1 alpha also induces granulocyte-macrophage colony-stimulating factor in immature normal bone marrow cells

The cytokine interleukin-1 (IL-1) plays a role in the regulation of normal as well as leukemic hematopoiesis. In acute myeloid leukemia (AML), IL-1 induces autocrine granulocyte/macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF) production, and these factors may then synergistically induce proliferation in AML blast cells. In this report, we show that IL-1 stimulates DNA synthesis of highly enriched normal bone marrow blast cells (CD34 positive, adherent cell depleted, CD3/CD14/CD15 negative). The stimulative effect of IL-1 can be blocked with neutralizing anti-TNF alpha and anti-GM-CSF antibodies and, most efficiently, by the combination of anti-TNF alpha and anti-GM-CSF, but not with anti-G-CSF antibody, suggesting that IL-1-induced proliferation was initiated through TNF and GM-CSF release. Concentrations of TNF and GM-CSF increased in the culture medium of normal bone marrow blast cells after IL-1 induction. Of the IL-1-induced cells, 12% were positive for GM-CSF mRNA by in situ hybridization, as opposed to 6% of non-induced cells. Thus, in addition to its effect on leukemic blast cells, IL-1 also acts on normal marrow blast cells. We propose a scheme where IL-1 stimulation of normal bone marrow blast cells leads to the induction of TNF alpha and GM-CSF, which in association stimulate DNA synthesis efficiently according to a paracrine or autocrine mechanism within the marrow blast cell compartment.

Synergistic effects between GM-CSF and G-CSF or M-CSF on highly enriched human marrow progenitor cells

The human multilineage hematopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF) induces multipotent, erythroid, and eosinophil colony formation from highly enriched normal bone marrow cells. We have examined the effects of GM-CSF combined with granulocyte-CSF (G-CSF) or macrophage-CSF (M-CSF) on the monolineage granulocytic, eosinophilic, and macrophage progenitor cells (CFU-G, CFU-Eo, and CFU-M) in accessory cell depleted marrow fractions. GM-CSF effects were assessed in direct comparison with those of interleukin-3 (IL-3) plus G-CSF or M-CSF. GM-CSF strongly synergized with G-CSF in the formation of granulocytic colonies with respect to number and size and enhanced the in vitro survival of CFU-G. More immature cells were present in colonies induced by the mixture of GM-CSF and G-CSF than by G-CSF alone. GM-CSF also synergized with M-CSF in the formation of macrophage colonies (number and size). The addition of G-CSF and M-CSF did not influence eosinophil colony formation induced by GM-CSF or IL-3. Experiments directly comparing GM-CSF and IL-3 revealed that the effects of GM-CSF on G and M colony-forming cells were significantly greater than those of IL-3. The potent positive effects between GM-CSF and G-CSF as well as between GM-CSF and M-CSF provide a powerful mechanism of amplification of granulopoiesis and monocytopoiesis.

Effects of human interleukin-3 on granulocytic colony-forming cells in human bone marrow

Human multilineage colony-stimulating factor (multi-CSF)/interleukin-3 (IL-3) induces colony formation from CFU-GEMM, BFU-E, and CFU-Eo when applied to in vitro cultures of highly enriched hematopoietic progenitor cells. No granulocytic colonies are formed in response to IL-3. However, with appropriate assays, we demonstrate that IL-3 increases the size of G-CSF-induced granulocytic colonies; these colonies contain greater proportions of immature cells as compared with colonies stimulated by G-CSF alone. Furthermore, IL-3 promotes the survival of CFU-G in vitro, whereas in cultures not supplemented with IL-3, CFU-G extinguish within seven days. We conclude that IL-3, although it does not stimulate granulocytic colony formation by itself, regulates the survival and proliferative rate of granulocytic progenitors.

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates immature marrow precursors but no CFU-GM, CFU-G, or CFU-M

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) has been described as a multilineage growth factor that induces in vitro colony formation from erythroid burst-forming units (BFU-E), eosinophil colony-forming units (CFU-Eo), and multipotential CFU (CFU-GEMM) as well as from granulocyte-macrophage CFU (CFU-GM), granulocyte CFU (CFU-G), and macrophage CFU (CFU-M). In this paper we provide evidence indicating that GM-CSF, when tested for its stimulating capacities expressed upon highly enriched hematopoietic progenitor cells (CD34+/monocyte-depleted), is unable to induce colonies from CFU-GM, CFU-G, or CFU-M. Only BFU-E, CFU-Eo, and CFU-GEMM were stimulated, and thus GM-CSF induces a similarly restricted spectrum of progenitor cells as does recombinant human interleukin 3 (IL-3). We then compared the relative stimulating potencies of GM-CSF and IL-3 by measuring colony numbers of CFU-GEMM, BFU-E, and CFU-Eo generated from CD34+ progenitor cells. IL-3 and GM-CSF as single factors were equally active in stimulating CFU-GEMM, but the combination of both factors produced additive stimulative effects upon CFU-GEMM. IL-3 was a more potent stimulus of BFU-E, and GM-CSF was the more active stimulating factor for CFU-Eo. We conclude that GM-CSF and IL-3, although stimulating the outgrowth of identical types of progenitor cells, particularly differ as regards their comparative quantitative efficiency of stimulation.

Non-Hodgkin lymphoma with unique localization in the kidneys presenting with acute renal failure

An unusual case of acute renal failure due to infiltration of the kidneys by non-Hodgkin lymphoma is described. The diagnosis was made by renal biopsy. Extensive clinical, laboratory, and radiological examination revealed that the kidneys were the only localization of the lymphoma.