Transgenic and knock-out mice: models of neurological disease

COX5A Plays a Vital Role in Memory Impairment Associated With Brain Aging via the BDNF/ERK1/2 Signaling Pathway

Cytochrome c oxidase subunit Va (COX5A) is involved in maintaining normal mitochondrial function. However, little is known on the role of COX5A in the development and progress of Alzheimer’s disease (Martinez-Losa et al., 2018). In this study, we established and characterized the genomic profiles of genes expressed in the hippocampus of Senescence-Accelerated Mouse-prone 8 (SAMP8) mice, and revealed differential expression of COX5A among 12-month-aged SAMP8 mice and 2-month-aged SAMP8 mice. Newly established transgenic mice with systemic COX5A overexpression (51% increase) resulted in the improvement of spatial recognition memory and hippocampal synaptic plasticity, recovery of hippocampal CA1 dendrites, and activation of the BDNF/ERK1/2 signaling pathway in vivo. Moreover, mice with both COX5A overexpression and BDNF knockdown showed a poor recovery in spatial recognition memory as well as a decrease in spine density and branching of dendrites in CA1, when compared to mice that only overexpressed COX5A. In vitro studies supported that COX5A affected neuronal growth via BDNF. In summary, this study was the first to show that COX5A in the hippocampus plays a vital role in aging-related cognitive deterioration via BDNF/ERK1/2 regulation, and suggested that COX5A may be a potential target for anti-senescence drugs.

Neurotransmitter depletion may be a cause of dementia pathology rather than an effect

BACKGROUND

There is widespread loss of acetylcholine and other neurotransmitters in Alzheimer's disease and vascular dementia. It has generally been assumed that death of neurons causes neurotransmitter loss, but alternatively neurotransmitter depletion itself may at least contribute to neurodegeneration.

PRESENTATION OF THE HYPOTHESIS

Transgenic mice and pigs with inducible 50% depletion of acetylcholine, dopamine, norepinephrine, serotonin, gamma-aminobutyric acid (GABA) and corticotrophin releasing factor will reproduce Alzheimer's disease or vascular dementia neuropathology, and pharmacologically restoring neurotransmitters will attenuate neuronal injury.

TESTING THE HYPOTHESIS

Through nuclear transfer cloning, transgenic mice and pigs would be created with transgenes on one X chromosome, so that transgenes would only be expressed in half of all cells in female animals. Transgenes would encode tetracycline-inducible short hairpin RNA (shRNA) designed to form small interfering RNA (siRNA) to knock down neurotransmitter biosynthesis in late adulthood. Transgene expressing neurons could be readily identified in tissue sections with fluorescent reporter genes. Cholinesterase inhibitors, antidepressants, benzodiazepines and CRF would then be administered in an attempt to rescue degenerating neurons.

IMPLICATIONS OF THE HYPOTHESIS

The mice and pigs could serve as an important new model for the pathogenesis of dementia, especially if pharmacologically restoring neurotransmitters rescues degenerating neurons. The animals may also be useful for as models for other disorders such as multi-system atrophy, Parkinson's disease, and depression.

Rodent models for dystonia research: Characteristics, evaluation, and utility

A large number of different genetic and acquired disorders of the nervous system may be associated with dystonia. To elucidate its pathogenesis and to facilitate the discovery of potential novel treatments, there has been a growing interest in the development of animal models and particularly rodent models. Multiple animal models for dystonia have now been developed and partially characterized. The results obtained from studies of these models often lead in very different directions, in part because the different models target different aspects of a very heterogeneous disorder. A recent workshop addressed four main issues affecting those who conduct dystonia research with animal models, including the different ways in which dystonic disorders can be modeled in rodents, key features that constitute a useful model, methods used in the evaluation of these models, and recommendations for future research. This review summarizes the main outcomes of this conference. 2005 Movement Disorder Society.

A single vector containing modified cre recombinase and LOX recombination sequences for inducible tissue-specific amplification of gene expression

The selective alteration of the genome using Cre recombinase to target the rearrangement of genes flanked by LOX recognition sequences has required the use of two separate genetic constructs in trans, one containing cre and the other containing the gene of interest flanked by LOX sites. We have developed a strategy in which both the cre recombinase gene and LOX recombination sites may be cloned within a single vector in cis. This method uses a modified form of Cre (CREM) that contains alterations to the 5' region including the introduction of a Kozak consensus sequence and insertion of a functional intron. This system allows for the inducible, tissue-specific activation or inactivation of gene expression in a single vector and can be utilized for the 300-fold amplification of gene expression from a weak promoter. This approach can be applied to targeting strategies for generating genetically altered mice and gene therapy.

Free flap transplantation in mice

A new model is presented that adapts the standard experimental groin free flap model to the mouse. The femoral vessels upon which the microvascular anastomoses are based are very small (0.2-0.4 mm diameter in the artery), making this a technically challenging exercise. A 100% patency was achieved for flap replantation in ICR (outbred) mice. Success rates for flap transplantation in Balb/C (syngeneic) mice rose from 20 to 75% with modification of the anastomoses from end-to-end to end-to-side procedures. This model offers new avenues of investigation when combined with recently developed transgenic mouse models.

Models of experimental bacterial meningitis. Role and limitations

The seriousness of bacterial meningitis has encouraged the development of animal models that characterize complex pathogenetic and pathophysiologic mechanisms, provide evaluation of pharmacokinetic and antimicrobial effects of antibiotics (especially since the worldwide emergence of multiresistant bacteria), and establish new adjuvant treatment strategies (e.g., use of anti-inflammatory agents). The information obtained from an animal model depends on the site of inoculation. For example, using intranasal, intravenous, subcutaneous, or intraperitoneal inoculation, it is the bacterial and host factors that determine the development of bacteremia and the potential for a pathogen to invade the central nervous system that primarily are studied. In contrast, experimental models using direct inoculation into the cerebrospinal fluid can reliably produce lethal infections over a predictable time course. Furthermore, because adult animals will not reliably develop meningitis after intranasal or intraperitoneal challenge, infant animals are used. Because these models bypass the natural dissemination of bacteria from the intravascular compartment to the central nervous system, the pathogenesis is artificial. These models, however, are extremely useful for the study of pathogen and host factors leading to meningeal inflammation and resulting complications, and for evaluating potentially useful agents for treatment therapy. During the past decade, the design of clinical studies has been stimulated by findings obtained from these animal models.

Age-dependent increase in ischemic brain injury in wild-type mice and in mice lacking the inducible nitric oxide synthase gene

The authors investigated the influence of age on the outcome of cerebral ischemia in wild-type mice and in mice with a deletion of the inducible nitric oxide synthase (iNOS) gene. The middle cerebral artery was permanently occluded in iNOS-null mice and in wild-type (C57BL/6) controls aged 4, 8, 16, and 24 weeks. Infarct volume was determined in thionin-stained brain sections 4 days after permanent middle cerebral artery occlusion. No differences in forebrain volume were found among wild-type and iNOS-null mice at the ages studied (P > 0.05). In C57BL/6 mice (n = 5 to 6/group), neocortical infarct volume corrected for swelling was 28 +/- 5 mm3 in 4-week-old mice, 28 +/- 3 at 8 weeks, 35 +/- 4 at 16 weeks, and 37 +/- 6 at 24 weeks (mean +/- SD). iNOS-null mice (n = 5 to 6/group) had smaller infarcts than wild-type controls at all ages (P < 0.05). However, the magnitude of the reduction was greater in 4-week-old (-29% +/- 10%) or 8-week-old mice (-24% +/- 8%), than in 16-week-old (-14% +/- 10%) or 24-week-old mice (-11% +/- 6%). Neurologic deficit scores improved significantly between 24 and 96 hours in 4- and 8-week-old iNOS-null mice compared with age-matched wild-type mice (P < 0.05). However, in 16- or 24-week-old iNOS-null mice, neurologic deficits did not improve (P > 0.05). The authors conclude that in iNOS-/- and in wild-type mice, the size of the infarct produced by occlusion of the middle cerebral artery is larger in older than in younger mice. However, the reduction in infarct volume observed in iNOS-null mice is age-dependent and is greatest at 1 to 2 months of age. Therefore, age is a critical variable in studies of focal cerebral ischemic damage, both in wild-type mice and in mouse mutants.

Behavioural analysis and susceptibility to CNS injury of four inbred strains of mice

Interpretation of data from gene targeting studies can be confounded by the inherent traits of the background inbred strains used in the generation of transgenic and null mutant mice. We have therefore compared the behaviour and response to CNS injury of four inbred strains commonly used in molecular genetic studies to produce models of neurological disease. Adult, male 129/Ola, BALB/c, C57BL/6 and FVB/N mice (2-4 months) were initially subjected to behavioural tests that comprised a neurological examination, determination of motor function and cognitive testing in the Morris water maze. Also the response to CNS injury following an acute kainic acid (KA) challenge (30 mg kg-1, i.p.) was determined. The 129/Ola and BALB/c strains showed significant motor deficits when compared with the C57BL/6 and FVB/N strains. In contrast, only the FVB/N strain showed evidence of apparent cognitive impairments in the water maze as evidenced by increased pathlengths to locate the escape platforms and impaired performance in a probe trial. In addition, the FVB/N strain showed the most severe seizure response and mortality rate (62%) following administration of KA (30 mg kg-1, i.p.). These behavioural changes were also associated with a greater degree of cell body and synaptophysin loss in the pyramidal CA3 hippocampal cell layer and astrogliosis 72-h post-dose. These data suggest that the FVB/N strain may not be the most suitable background strain for the development of new transgenic mice for the study of genes implicated in the learning and memory process.

Cardiotrophin-1 requires LIFRbeta to promote survival of mouse motoneurons purified by a novel technique

The cytokines ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) signal through a receptor complex formed between two transmembrane proteins, gp130 and LIFRbeta. In addition, CNTF also uses a ligand-binding component which is anchored to the cell membrane. In the case of cardiotrophin-1 (CT-1), LIFRbeta is also required in cardiomyocytes, but this has not been proven in neurons, and published data suggest that motoneurons may use a different receptor complex. We used Lifrbeta knockout mice to assess the requirement for this receptor component in the signal transduction of CT-1 in motoneurons. To study purified motoneurons from such mutants, we have developed a method allowing for isolation of highly purified mouse motoneurons. This protocol is based on the immunoaffinity purification of motoneurons using antibodies against the extracellular domain of the neurotrophin receptor, p75, followed by cell sorting using magnetic microbeads. We show that CNTF, LIF, and CT-1 are unable to promote the survival of motoneurons derived from homozygous Lifrbeta-/- mutant embryos. Thus, LIFRbeta is absolutely required to transduce the CT-1 survival signal in motoneurons.

Using knockout and transgenic mice to study neurophysiology and behavior

Reverse genetics, in which detailed knowledge of a gene of interest permits in vivo modification of its expression or function, provides a powerful method for examining the physiological relevance of any protein. Transgenic and knockout mouse models are particularly useful for studies of complex neurobiological problems. The primary aims of this review are to familiarize the nonspecialist with the techniques and limitations of mouse mutagenesis, to describe new technologies that may overcome these limitations, and to illustrate, using representative examples from the literature, some of the ways in which genetically altered mice have been used to analyze central nervous system function. The goal is to provide the information necessary to evaluate critically studies in which mutant mice have been used to study neurobiological problems.

Transgenic mice in drug dependence research

Transgenic mice with null mutation of specific genes of the central nervous system obtained by homologous recombination, called also knock-out mice, have been recently used by behavioural neuroscientists to understand better the relevance of certain biological mechanisms of drug dependence or addiction. This article reviews some of the main contributions to this fastly developing field. As addictive drugs exert similar reinforcing effects both in humans and other mammals, changes in behavioural performance produced by the motivational effects of the addictive drugs in knock-out mice can give important information about the relevance of that particular gene product (eg a neurotransmitter receptor) for the pathogenicity of substance abuse disorders. In same cases the deletion of a given gene for a neurotransmitter receptor involved in the action of addictive drugs is associated with a phenotype that reproduces the effects obtained by the pharmacological administration of an antagonist for the same receptor. In other instances, surprising results are obtained, the most striking being the evidence that mice lacking the dopamine transporter gene, the most important binding site of cocaine, retain the capability to self-administer cocaine intravenously. Because the gene deletion is operative during embryogenesis, some adaptive compensatory mechanisms may produce unexpected results, suggesting caution in the interpretation of these results. The advent of tissue-specific inducible knock-out mice will soon produce a second revolution in the field of substance abuse research.

Behavior in mice with targeted disruption of single genes

The use of mice with targeted deletion, or knockout, of specific genes provides a relatively new approach to establish the molecular bases of behavior. As with all ablation studies, the interpretation of behavioral data may be limited by the technique. For example, indirect effects of the missing gene may affect behavior, rather than the missing gene per se. Also, because the missing gene might affect many developmental processes throughout ontogeny and because up-regulation or compensatory mechanisms may be activated in knockouts, behavioral data from mice with targeted gene deletions should be interpreted with caution. The development of conditional knockouts, in which a specific gene can be inactivated any time during ontogeny, should allow investigators to avoid these conceptual shortcomings associated with behavioral data from knockouts in the near future. The behavioral alterations reported in knockout mice are reviewed here. Many dramatic changes in complex motivated behaviors including aggression, sexual, ingestive, and parental behaviors, have been reported for knockouts. There have also been many reports of alterations in sensorimotor abilities and spontaneous activity, as well as impairments in balance, coordination, and gait. Impaired learning and memory have also been reported for mice with targeted disruption of specific genes. Taken together, the use of knockouts will provide an important new tool to understand the mechanisms underlying behavior.

D1 receptors mediate dopamine action in the fetal suprachiasmatic nuclei: studies of mice with targeted deletion of the D1 dopamine receptor gene

Studies in rodents suggest the presence of a dopaminergic system that influences the function of a biological clock in the hypothalamic suprachiasmatic nuclei (SCN). To provide insights into mechanisms of dopamine action in the SCN, we studied transgenic mice that had either one allele (+¿-) or both alleles (-/-) of the D1 dopamine receptor gene deleted, along with normal (+/+) littermates. As expected, receptor labelling autoradiography studies using [125I]SCH 23982 showed a complete absence of D1 dopamine receptor binding sites in the SCN of -/- animals. When pregnant mice from +¿- x +¿- matings were injected with the D1 receptor agonist SKF 38393, or the dopamine reuptake blocker GBR 12909 at day 19 of gestation, c-fos mRNA expression was observed in the SCN of +/+ fetuses. In contrast, c-fos mRNA induction was not seen in -/- or +¿- litter mates. Injection of cocaine into pregnant dams also resulted in robust SCN c-fos mRNA expression in +/+ mice. Increases in SCN c-fos mRNA expression were also seen in +¿- and -/- mice suggesting that cocaine action in the SCN involves both D1 receptor-dependent and -independent mechanisms. Collectively, our studies of transgenic mice deficient in D1 receptors support the presence of a functional dopaminergic system in the fetal SCN. We also identify D1 receptors as the prominent transducer of dopamine action in the fetal SCN.

Recent advances in transgenic technology

Techniques that allow modification of the mammalian genome have made a considerable contribution to many areas of biological science. Despite these achievements, challenges remain in two principal areas of transgenic technology, namely gene regulation and efficient transgenic livestock production. Obtaining reliable and sophisticated expression that rivals that of endogenous genes is frequently problematic. Transgenic science has played an important part in increasing understanding of the complex processes that underlie gene regulation, and this in turn has assisted in the design of transgene constructs expressed in a tightly regulated and faithful manner. The production of transgenic livestock is an inefficient process compared to that of laboratory models, and the lack of totipotential embryonic stem (ES) cell lines in farm animal species hampers the development of this area of work. This article highlights recent progress in efficient trans gene expression systems, and the current efforts being made to find alternative means of generating transgenic livestock.

The use of genetic "knockout" mice in behavioral endocrinology research

The production of mice with specific deletion of targeted genes (knockouts) has provided a useful tool in understanding the mechanisms underlying behavior. There are many opportunities with this new tool for behavioral neuroendocrinology, specifically, and behavioral biology, generally. Although this genetic technique offers new opportunities to study the mechanisms of behavior, as with all behavioral techniques there are some potential limitations. For example, the products of many genes are essential to normal function, and inactivating the gene may prove lethal or induce gross morphological or physiological abnormalities that can complicate interpretation of discrete behavioral effects. Unexpected compensatory or redundancy mechanisms might be activated when a gene is missing and cloud interpretation of the normal contribution of the gene to behavior. Behavioral tests study the effects of the missing gene (and gene product), not the effects of the gene directly. This conceptual shortcoming can be overcome in the same way that it is overcome in other types of ablation studies, by collecting converging evidence using a variety of pharmacological, lesion, and genetic manipulations. Finally, because mammalian genome mapping is currently focused on mice (Mus musculus), standardized behavioral testing of mice should be adopted. Against those disadvantages are several important advantages to using knockout mice in behavioral research: (1) disabling a gene is often a very precise and "clean" ablation, (2) the effects of the gene product can be abolished without the side-effects of drugs, and (3) genetic manipulations may be the only way to determine the precise role of many endogenous factors on behavior. The use of new inducible knockouts, in which the timing and placement of the targeted gene disruption can be controlled, will be an extremely important tool in behavioral endocrinology research.

Murine models of brain aging and age-related neurodegenerative diseases

In the past, structural changes in the brain with aging have been studied using a variety of animal models, with rats and nonhuman primates being the most popular. With the rapid evolution of mouse genetics, murine models have gained increased attention in the neurobiology of aging. The genetic contribution of age-related traits as well as specific mechanistic hypotheses underlying brain aging and age-related neurodegenerative diseases can now be assessed by using genetically-selected and genetically-manipulated mice. Against this background of increased demand for aging research in mouse models, relatively few studies have examined structural alterations with aging in the normal mouse brain, and the data available are almost exclusively restricted to the C57BL/6 strain. Moreover, many older studies have used quantitative techniques which today can be questioned regarding their accuracy. Here we review the state of knowledge about structural changes with aging in outbred, inbred, genetically-selected, and genetically-engineered murine models. Moreover, we suggest several new opportunities that are emerging to study brain aging and age-related neurodegenerative diseases using genetically-defined mouse models. By reviewing the literature, it has become clear to us that in light of the rapid progress in genetically-engineered and selected mouse models for brain aging and age-related neurodegenerative diseases, there is a great and urgent need to study and define morphological changes in the aging brain of normal inbred mice and to analyze the structural changes in genetically-engineered mice more carefully and completely than accomplished to date. Such investigations will broaden knowledge in the neurobiology of aging, particularly regarding the genetics of aging, and possibly identify the most useful murine models.

Role of vimentin in early stages of neuritogenesis in cultured hippocampal neurons

Vimentin is expressed initially by nearly all neuronal precursors in vivo, and is replaced by neurofilaments shortly after the immature neurons become post-mitotic. Moreover, both vimentin and neurofilaments can be detected transiently within the same neurite, leaving open the possibility that vimentin may play a role in the early stages of neuritogenesis. In the present study, cultured hippocampal neurons, which transiently express vimentin in culture, were treated with sense- and antisense-oriented deoxyoligonucleotides encoding regions of the vimentin sequence that overlap the translation initiation codon. Antisense oligonucleotide treatment reduced vimentin-immunoreactivity to background levels. Moreover, while 90-100% of cultured hippocampal neurons elaborated neurites within the first 24 hr following plating, only 24-30% did so in the presence of vimentin antisense oligonucleotides. Inhibition of neurite outgrowth was reversible following removal of antisense oligonucleotide. These findings substantiate earlier studies in neuroblastoma cells, indicating a possible role for vimentin in the initiation of neurite outgrowth.

A combined stereotaxic adaptor and anaesthesia apparatus for microdialysis studies in small rodents

Intracerebral microdialysis in the bank vole (Clethrionomys glareolus) challenges the accuracy and precision of the stereotaxic implantation technique because of the small brain size. In this paper, a miniaturized stereotaxic head holder is described that allows precise alignment of bone landmarks on the skull and prevents all movement after fixation by clamping the skull symmetrically at the os parietale and at the os nasale. In addition, the head holder is adapted for inhalation anaesthetic delivery in order to ensure stable anaesthetic depth over several hours. The system is not restricted to bank voles but can be readily applied to other small experimental animals, which could lead to a more widespread use of the microdialysis technique in mice.

The gene for hereditary sensory neuropathy type I (HSN-I) maps to chromosome 9q22.1-q22.3

Hereditary sensory neuropathy type I (HSN-I, also known as hereditary sensory and autonomic neuropathy type I (HSAN-I), or hereditary sensory radicular neuropathy) is an autosomal dominant disorder that is the most common of a group of degenerative disorders of sensory neurons. HSN-I was initially recognized as a disease that produced mutilating ulceration leading to amputation of digits (Fig. 1). It was given names such as familial ulcers with mutilating lesions of the extremities and perforating ulcers with osseous atrophy. The disease involves a progressive degeneration of dorsal root ganglion and motor neurons, leading to distal sensory loss and later distal muscle wasting and weakness and variable neural deafness. Sensory deficits include loss of all modalities, particularly loss of sensation to pain and temperature. Skin injuries may lead to chronic skin ulcers, osteomyelitis, and extrusion of bone fragments, especially the metatarsals. Onset of symptoms is in the second or later decades. We undertook a genome screen using linkage analysis in four Australian HSN-I kindreds. We now show that the HSN1 gene maps to an 8-centiMorgan (cM) region flanked by D9S318 and D9S176 on chromosome 9q22.1-q22.3. Multipoint linkage analysis suggests a most likely location at D9S287, within a 4.9-cM confidence interval.

The principles of gene therapy for the nervous system

Research pertaining to gene transfer into cells of the nervous system is one of the fastest growing fields in neuroscience. An important application of gene transfer is gene therapy, which is based on introducing therapeutic genes into cells of the nervous system by ex vivo or in vivo techniques. With the eventual development of efficient and safe vectors, therapeutic genes, under the control of a suitable promoter, can be targeted to the appropriate neurons or glial cells. Gene therapy is not only applicable to the treatment of genetic diseases of the nervous system and the control of malignant neoplasia, but it also has therapeutic potential for acquired degenerative encephalopathies (Alzheimer's disease, Parkinson's disease), as well as for promoting neuronal survival and regeneration in various pathological states.

Adenovirus-mediated expression of a reporter gene in thalamocortical cocultures

Organotypic cocultures of thalamic and cortical explants have recently been used to study the development of the thalamocortical axonal network in the mammalian neocortex. To explore the possibility of genetically manipulating organotypic explants, rat thalamocortical (TC) cocultures were infected with the recombinant adenovirus, Adv/RSV beta gal. Infection of the cortical explants resulted in long-term expression (2 weeks) of the reporter gene (beta-galactosidase) with no significant alterations to the structural integrity of the explants. By micro-injecting the adenoviruses into cortical explants a significant degree of spatial control over reporter gene expression was obtained. DiI-labeled axonal projections from thalamic explants into infected (n = 116) and control cortical (n = 120) explants were also analyzed. There was no significant difference in the extent or degree of TC ingrowth into infected or control cortical explants. Thalamic explants were also efficiently infected with the Adv/RSV beta gal virus. While the pattern and extent of TC ingrowth from infected thalamic explants was similar to controls, the percentage of viable, infected thalamic explants was decreased. These experiments were necessary precursors for future studies using recombinant adenoviruses and organotypic cocultures. Genetic manipulation of these cocultures should enable the dissection of proteins involved in the development of axonal networks in the mammalian neocortex, using a system amenable to direct manipulation and observation.

Transgenic animals as models in the study of the neurobiological role of polyamines

Natural polyamines, putrescine, spermidine and spermine, exhibit a number of neurophysiological and metabolic effects in brain preparations. In the in vitro studies, several specific sites of action have been identified such as ion channels, transmitter release and Ca2+ homeostasis. Polyamines have been linked to the development of neuronal degeneration caused by, for instance, epileptic seizures and stroke. The role of endogenous polyamines in the functioning brain is not clear, however. We review the work carried out using state-of-the-art transgenic animal models for polyamine research. A number of transgenic mouse lines carrying human ornithine decarboxylase, spermidine synthase and S-adenosylmethionine decarboxylase gene have been generated. Of these animals those with ornithine decarboxylase transgene show an extensive and constitutive expression of the enzyme in the brain with an exceedingly high putrescine concentration, a phenotype that is not encountered under physiological conditions. In this article we review the neurometabolic, behavioural and histological data that has been obtained from these transgenic mice.

Transgenic models for eye malformations

Several lines of transgenic mice developing eye malformations have been described in the literature and appear to be of increasing interest for the study of eye teratology in humans, since gene expression and regulation can be studied in the developing animal. Transgenic applications are briefly described here and an overview of existing transgenic mouse models carrying different eye abnormalities is given according to the major diagnosis (e.g., cataract, microphthalmia, anterior segment dysgenesis, retinal dysplasia). Interestingly, many transgenic models exhibit pathological findings similar to those observed in human pediatric ophthalmology. Unfortunately, detailed embryological studies in transgenic mice bearing congenital eye malformations are not available for all lines. Thus, the importance of creating further transgenic models to study the function of morphogenes and growth factors in eye development is also discussed.

Cerebrovascular responses under controlled and monitored physiological conditions in the anesthetized mouse

Control of physiological parameters such as respiration, blood pressure, and arterial blood gases has been difficult in the mouse due to the lack of technology required to monitor these parameters in small animals. Here we report that anesthetized and artificially ventilated mice can be maintained under physiological control for several hours with apparently normal cerebrovascular reactivity to hypercapnia and mechanical vibrissal stimulation. SV-129 mice were anesthetized with urethane (750 mg/kg i.p.) and alpha-chloralose (50 mg/kg i.p.), intubated, paralyzed, and artificially ventilated. Respiratory control was maintained within physiological range by reducing the inspiratory phase of the respiratory cycle to < 0.1 s and by adjusting end-tidal CO2 to give a PCO2 of 35 +/- 3 mm Hg. In these mice, mean arterial pressure (95 +/- 9 mm Hg), heart rate (545 +/- 78 beats/min), and arterial pH (7.27 +/- 0.10) could be maintained for several hours. Body temperature was kept at 36.5-37.5 degrees C. We observed stable regional CBF (rCBF) measurements (as determined by laser-Doppler flowmetry) when systemic arterial blood pressure was varied between 40 and 130 mm Hg. Hypercapnia led to a 38 +/- 15% (5% CO2) and 77 +/- 34% (10% CO2) increase in rCBF. Mechanical stimulation of contralateral vibrissae for 1 min increased rCBF by 14 +/- 4%. Changes in rCBF compare favorably with those observed previously in another rodent species, the Sprague-Dawley rat. After placement of a closed cranial window, cerebrovascular reactivity to hypercapnia and whisker stimulation was intact and well maintained during 2-h superfusion with artificial CSF.

Rapid appearance of beta-amyloid precursor protein immunoreactivity in glial cells following excitotoxic brain injury

Clinical and experimental data have indicated an up-regulation of amyloid precursor protein (APP) after various types of CNS injury. In the present study the cellular source of lesion-induced APP has been investigated in a neurotoxic CNS model. Quinolinic acid injection into the striatum results in neuronal degeneration, while glial cells survive. APP immunoreactivity was detected in glial cells starting at postoperative day 3 and persisted until day 21, the last time point studied. Double immunocytochemistry identified the majority of APP-immunoreactive cells as glial fibrillary acidic protein-immunoreactive astrocytes. There was no evidence of amyloid fibril deposition during this time. It is concluded that following excitotoxic neuronal degneration APP is mainly produced by reactive astrocytes in the lesioned area.