Effect of whole-milk allowance on liveweight gain and growth of parenchyma and fat pads in the mammary glands of dairy heifers at weaning

The rates of development of 2 tissues in mammary glands, parenchyma (PAR) and the mammary fat pad (MFP), in response to nutrition in early life might have a major bearing on lifetime milk production. Historical studies reported that feeding greater amounts of dietary nutrients from postweaning to puberty increased growth rates of heifers and stimulated the growth of MFP at the expense of PAR, which might suggest compromised mammary development and future milk production. The current study sought to determine if a higher volume of whole milk (8 vs. 4 L/d) offered to calves would increase rates of growth and development of PAR in mammary glands at weaning (1 to 12 wk). To measure these tissues, we developed 2 simple methods to assess the size of PAR and MFP at the time of screening using ultrasound. We report that calves offered 8 L/d of whole milk had greater rates of growth until weaning (0.86 ± 0.06 vs. 0.81 ± 0.09 kg/d), compared with calves offered 4 L/d. Ultrasonography showed that despite the faster rates of growth in calves offered 8 L/d of milk/d, the ratio of PAR:MFP depth was 40% less at weaning in the front glands (34%) compared with calves offered 4 L of milk/d. Rear glands were less impaired. The ultrasound methods developed here might be useful to monitor the development of mammary glands in response to different nutritional regimens during the preweaning period.

A novel role of circadian transcription factor DBP in hippocampal plasticity

In neurons, a variety of extracellular stimuli are capable of inducing transcriptional events that underlie complex processes ranging from learning to disease. The mechanisms linking these long-lasting cellular modifications to behavior remain to be established. Here, we show by microarray analysis that hippocampal activation of glucagon-like peptide-1 receptor (GLP-1R), which is associated with improved learning and neuroprotection, results in suppression of the transcription factor DBP (albumin D-site-binding protein). Recombinant adeno-associated virus (rAAV) based gene expression of DBP in the hippocampus of adult rats caused upregulation of mRNAs encoding constituents of the molecular clock, and the DBP target gene, pyridoxal kinase. Behaviorally, DBP over expression inhibited spatial learning but not memory, and enhanced susceptibility to kainate-induced seizures. This phenotype was paralleled by the activation of MAP kinase in dendritic regions of hippocampal neurons in vivo. These data suggest that DBP may represent an important transcriptional link between GLP-1R activation and neuroplasticity in the hippocampus.

Restoration of aspartoacylase activity in CNS neurons does not ameliorate motor deficits and demyelination in a model of Canavan disease

Canavan disease is an early onset leukodystrophy associated with psychomotor retardation, seizures, and premature death. This disorder is caused by mutations in the gene encoding the enzyme aspartoacylase (ASPA). Normally, ASPA is enriched in oligodendrocytes and ASPA deficiency results in elevated levels of its substrate molecule, N-acetylaspartate (NAA), brain edema, and dysmyelination. Using adeno-associated virus, we permanently expressed ASPA in CNS neurons of the tremor rat, a genetic model of Canavan disease, and examined the efficacy of the treatment by monitoring NAA metabolism, myelination, motor behavior, and seizures. Assessment of ASPA protein and enzyme activity in whole brain hemispheres showed restoration to normal levels as long as 6 months after treatment. This finding correlated with a reduction of NAA levels, along with a rescue of the seizure phenotype. However, gross brain pathology, such as dilated ventricles and spongiform vacuolization, was unchanged. Moreover, hypomyelination and motor deficits were not resolved by ASPA gene transfer. Our data suggest that NAA-mediated neuronal hyperexcitation but not oligodendrocyte dysfunction can be compensated for by neuronal ASPA expression.

AAV-mediated hippocampal expression of short and long Homer 1 proteins differentially affect cognition and seizure activity in adult rats

Homer proteins mediate molecular rearrangements leading to changes in spine morphology. This points to a role of Homer in learning and memory. Homer 1c features both the ligand binding domain and a coiled-coiled domain for self-multimerization. Homer 1a lacks the coiled-coiled domain. Here, we report a new isoform which we termed 1g, lacking the Homer ligand binding domain. We dissected the functional roles of the individual Homer 1 domains, encoded by Homer 1a, 1c, and 1g, in vivo. Recombinant adeno-associated virus (AAV)-mediated overexpression of these forms in the hippocampus of adult rats has opposing effects on learning behavior. Increased levels of Homer 1a impaired hippocampal-dependent memory, while Homer 1g and 1c slightly enhanced memory performance. Homer 1g induced anxiety. Moreover, AAV-Homer 1a animals showed attenuation of electrographic seizures in a model of status epilepticus. These results suggest that Homer 1 proteins play an active role in behavioral plasticity.

Identification and distribution of aspartoacylase in the postnatal rat brain

Aspartoacylase metabolizes N-acetylaspartic acid to produce L-aspartate and acetate. An aspartoacylase deficiency in humans is responsible for Canavan disease, a lethal autosomal recessive leukodystrophy. The role of aspartoacylase in the mammalian brain is unclear. Here we have generated and characterized a highly specific polyclonal antibody against aspartoacylase which recognizes a 37 kDa monomer and a dimer in normal but not in aspartoacylase-deficient rat tissue. Aspartoacylase protein expression sharply increases at P14, peaks at P28 and plateaus thereafter. Biochemical analysis reveals immunoreactivity in cytosolic but not in membrane fractions. Histologically, most abundant expression was observed in white matter tracts and thalamus. On the cellular level, aspartoacylase immunoreactivity is restricted to oligodendrocyte somata in both white and gray matter.

Immunological aspects of recombinant adeno-associated virus delivery to the mammalian brain

Recombinant adeno-associated viruses (rAAV) are highly efficient vectors for gene delivery into the central nervous system (CNS). However, host inflammatory and immune responses may play a critical role in limiting the use of rAAV vectors for gene therapy and functional genomic studies in vivo. Here, we evaluated the effect of repeated injections of five rAAV vectors expressing different genetic sequences (coding or noncoding) in a range of combinations into the rat brain. Specifically, we wished to determine whether a specific immune or inflammatory response appeared in response to the vector and/or the transgene protein after repeated injections under conditions of mannitol coinjection. We show that readministration of the same rAAV to the CNS is possible if the interval between the first and second injection is more than 4 weeks. Furthermore, our data demonstrate that rAAV vectors carrying different genetic sequences can be administered at intervals of 2 weeks. Our data therefore suggest that the AAV capsid structure is altered by the vector genetic sequence, such that secondary structures of the single-stranded genome have an impact on the antigenicity of the virus. This study provides guidelines for more rational design of gene transfer studies in the rodent brain and, in addition, suggests the use of repeated administration of rAAV as a viable form of therapy for the treatment of chronic diseases.

An oral vaccine against NMDAR1 with efficacy in experimental stroke and epilepsy

The brain is generally considered immunoprivileged, although increasing examples of immunological responses to brain antigens, neuronal expression of major histocompatibility class I genes, and neurological autoimmunity have been recognized. An adeno-associated virus (AAV) vaccine generated autoantibodies that targeted a specific brain protein, the NR1 subunit of the N-methyl-D-aspartate (NMDA) receptor. After peroral administration of the AAV vaccine, transgene expression persisted for at least 5 months and was associated with a robust humoral response in the absence of a significant cell-mediated response. This single-dose vaccine was associated with strong anti-epileptic and neuroprotective activity in rats for both a kainate-induced seizure model and also a middle cerebral artery occlusion stroke model at 1 to 5 months following vaccination. Thus, a vaccination strategy targeting brain proteins is feasible and may have therapeutic potential for neurological disorders.

Isolation, characterisation and cell growth-regulatory properties of kumara (sweet potato) trypsin inhibitors

Locally grown kumara (sweet potato; Ipomea batatis) was used as the starting point for the purification of a proteinase inhibitor. The purified inhibitor was highly specific for trypsin, and much less effective as an inhibitor of chymotrypsin. Two 22kDa variants were present, closely homologous to each other and to sporamin A, but with a single amino acid substitution (proline in place of serine, the second residue in mature sporamin A). One variant had the same N-terminus as sporamin A, whereas the other had a tripeptide N-terminal extension, which may represent an intermediate in the proteolytic processing of the precursor protein. A larger variant was apparently a disulphide-linked dimer of the monomeric inhibitor. A rabbit polyclonal antiserum prepared against the trypsin inhibitor reacted with all of these variants, but did not cross-react with commercially-available soybean proteinase inhibitors. The purified inhibitor did resemble other proteinase inhibitors in having a biphasic effect upon the proliferation of human fibroblasts, with a mitogenic action at low concentrations, and an inhibitory effect at higher concentrations.