Shape variation in cranium, mandible and teeth in selected mouse strains.

There are different strains of laboratory mouse used in many different fields. These strains differ anatomically. In order to determine these anatomical differences, shape analysis was conducted according to species. CD-1, C57bl/6 and Balb-c strains were preferred to study these differences. Forty-eight adult mouse strains belonging to these strains were utilized. The bones were photographed and geometric morphometry was applied to these photographs. Principal Component Analysis was applied to determine shape variations. In Principal component 1 for cranium, CD-1 and C57bl/6 strain groups showed different shape variations, while Balb-c strain group showed similar shape variations to the other strain groups. Principal Component 1 for the mandible separated the CD-1 and C57bl/6 strain groups in terms of shape variation. Principal Component 2 explained most of the variation between the C57bl/6 and CD-1 lineage groups. In PC1 for molars, the CD-1 group showed a different shape variation from the other groups. Mahalanobis distances and Procrustes distances were measured using Canonical variance analysis to explain the differences between the lineage groups. These measurements were statistically significant. For cranium, in canonical variate 1, CD-1 group of mouse and Balb-c group of mouse were separated from each other. In canonical variate 2, C57bl/6 group of mouse were separated from the other groups. For mandible, Balb-c group of mouse in canonical variate 1 and CD-1 group of mouse in canonical variate 2 were separated from the other groups. For molars, CD-1 group of mouse in canonical variate 1 and Balb-c group of mouse in canonical variate 2 were separated from the other groups. It was thought that these anatomical differences could be caused by genotypic factors as well as dietary differences and many different habits that would affect the way their muscles work.

Histological and computed tomographic characteristics of the sinonasal structure of BALB/c mice.

Mice models were used to study the pathogenesis of mice and human diseases. Although some mice models of allergic rhinitis and rhinosinusitis have been reported, no detailed anatomic, histological and computed tomographic comparative data of the normal murine sinus are available in the literature for new researchers to establish mice models. The purpose of this study was to clarify the histological and computed tomographic characteristics of the normal nasal sinus in BALB/c mice. Fifteen sinonasal specimens were collected. Five mice were subjected to micro-computed tomography imaging, and then dissected to observe its anatomic landmarks, and 10 mice were subjected to haematoxylin and eosin staining. Important anatomic landmarks were clearly demonstrated, including the ethmoturbinates, nasoturbinal, maxilloturbinate, ethmoid sinus, maxillary sinus, nasopharyngeal duct, nasolacrimal duct and vomeronasal organ. Full and typical sinonasal landmarks can be visualized by gross anatomy, micro-computed tomography imaging and haematoxylin and eosin staining, which will be useful for establishing the mouse models of nasal disease.

Impact of bedding volume on physiological and behavioural parameters in laboratory mice.

The standard housing temperature in animal facilities is substantially below the lower critical temperature of mice. This does not only endanger animal welfare, it can also jeopardize scientific research as cold stress has a major impact on mouse physiology. There is some evidence that deep bedding, comparable to nesting material, can help mice to reduce heat loss. Whenever changes are applied to the cage environment, the potential impact on experimental results, including variation, needs to be assessed. An increased variation can result in a conflict between reduction and refinement, when more animals are needed for significance due to the housing design. The aim of this study was to assess the impact of different bedding volumes (0.5 L, 1.5 L and 6 L per type III cage) on mean values and coefficient of variation (CV) of physiological (pentobarbital sleeping time, blood and anatomical parameters) and behavioural parameters (open-field and novel object recognition tests) of group-housed female and male BALB/c and C57BL/6 mice. A larger bedding volume did not interfere with the CVs, but influenced mean values of organ weights and tail lengths. Mice housed on deeper bedding showed a significant reduction in adrenal, liver, kidney and heart weights as well as an increase in tail lengths; these anatomical changes are akin to warm adaptation, and were previously observed for mice housed under warmer environments. A larger bedding volume appears to be a sensible way to reduce cold stress for laboratory mice without increasing variation in experimental results.

In vivo microscopic voxel-based morphometry with a brain template to characterize strain-specific structures in the mouse brain.

Hundreds of inbred mouse strains are established for use in a broad spectrum of basic research fields, including genetics, neuroscience, immunology, and cancer. Inbred mice exhibit identical intra-strain genetics and divergent inter-strain phenotypes. The cognitive and behavioral divergences must be controlled by the variances of structure and function of their brains; however, the underlying morphological features of strain-to-strain difference remain obscure. Here, in vivo microscopic magnetic resonance imaging was optimized to image the mouse brains by using an isotropic resolution of 80 µm. Next, in vivo templates were created from the data from four major inbred mouse strains (C57Bl/6, BALB/cBy, C3H/He, and DBA/2). A strain-mixed brain template was also created, and the template was then employed to establish automatic voxel-based morphometry (VBM) for the mouse brain. The VBM assessment revealed strain-specific brain morphologies concerning the gray matter volume of the four strains, with a smaller volume in the primary visual cortex for the C3H/He strain, and a smaller volume in the primary auditory cortex and field CA1 of the hippocampus for the DBA/2 strain. These findings would contribute to the basis of for understanding morphological phenotype of the inbred mouse strain and may indicate a relationship between brain morphology and strain-specific cognition and behavior.

Long-Term Provision of Environmental Resources Alters Behavior but not Physiology or Neuroanatomy of Male and Female BALB/c and C57BL/6 Mice.

Few studies have evaluated the long-term effects of providing environmental resources to mice. This consideration is important given that mice are often maintained in vivaria for months. We evaluated the effects of providing simple cage resources (wood wool, cotton nesting material, a plastic tunnel, and oat cereal) compared with standard housing (solid-bottom cage with hardwood chips) to group-housed adult male and female C57BL/6 and BALB/c mice (n = 20/sex/strain/group) over 6 mo to determine whether these resources had a lasting effect on animal physiology, anatomy, and behavior. Body weights increased in all groups over time but were proportionately higher in male and female BALB/c mice housed in resource-supplemented environments. Throughout the study, adding environmental resources had no effect on hematology and lymphocyte subsets, fecal corticoid metabolite levels, response to LPS injection, or dendritic spine length or density. Strain- or sex×environmentspecific changes occurred in dark-light activity and thermal nociceptive responses. Dominant agonistic behaviors, abnormal conspecific sexual behaviors, and social nonagonistic behaviors demonstrated sex and strain×environment interactions such that fewer maladaptive social behaviors were noted in mice that were provided with environmental resources. This association was particularly evident in male mice of both strains in resource-supplemented environments. A small but significant increase in brain weight:body weight ratios occurred in mice in resource-supplemented environments. Under the conditions evaluated here, consistent use of simple environmental resources had a positive long-term effect on the behavioral wellbeing of male and female BALB/c and C57BL/6 mice yet minimally affected other aspects of murine physiology and neuroanatomy.

Visual capabilities and cortical maps in BALB/c mice.

By combining behavioural analyses with intrinsic signal optical imaging, we analysed visual performance and visual cortical activity in the albino mouse strain BALB/c, which is increasingly being used as an animal model of neuropsychological disorders. Visual acuity, as measured by a virtual-reality optomotor system, was 0.12 cycles per degree (cyc/deg) in BALB/c mice and 0.39 cyc/deg in pigmented C57BL/6 mice. Surprisingly, BALB/c mice showed reflexive head movements against the direction of the rotating stimulus. Contrast sensitivity was significantly lower in BALB/c mice (45% contrast at 0.064 cyc/deg) than in C57BL/6 mice (6% contrast). In the visual water task, visual acuity was 0.3 cyc/deg in BALB/c mice and 0.59 cyc/deg in C57BL/6 mice. Thus, the visual performance of BALB/c mice was significantly impaired in both behavioural tests - visual acuity was ∼ 0.3 cyc/deg lower than in C57BL/6 mice, and contrast sensitivity was reduced by a factor of ∼ 8. In BALB/c mice, visual cortical maps induced by stimulation of the contralateral eye were normal in both activation strength and retinotopic map quality. In contrast, maps induced by ipsilateral eye stimulation differed significantly between the strains - activity in a region representing 15° to 19° elevation in the visual field was significantly weaker in BALB/c mice than in C57BL/6 mice. Taken together, our observations show that BALB/c mice, like the albino animals of other species, have a significantly lower visual performance than C57BL/6 mice and a modified cortical representation of the ipsilateral eye that may impair stereopsis. Thus, our results caution against disregarding vision as a confounding factor in behavioural tests of neuropsychological disorders.

Sociability and brain development in BALB/cJ and C57BL/6J mice.

Sociability--the tendency to seek social interaction--propels the development of social cognition and social skills, but is disrupted in autism spectrum disorders (ASD). BALB/cJ and C57BL/6J inbred mouse strains are useful models of low and high levels of juvenile sociability, respectively, but the neurobiological and developmental factors that account for the strains' contrasting sociability levels are largely unknown. We hypothesized that BALB/cJ mice would show increasing sociability with age but that C57BL/6J mice would show high sociability throughout development. We also hypothesized that littermates would resemble one another in sociability more than non-littermates. Finally, we hypothesized that low sociability would be associated with low corpus callosum size and increased brain size in BALB/cJ mice. Separate cohorts of C57BL/6J and BALB/cJ mice were tested for sociability at 19-, 23-, 31-, 42-, or 70-days-of-age, and brain weights and mid-sagittal corpus callosum area were measured. BALB/cJ sociability increased with age, and a strain by age interaction in sociability between 31 and 42 days of age suggested strong effects of puberty on sociability development. Sociability scores clustered according to litter membership in both strains, and perinatal litter size and sex ratio were identified as factors that contributed to this clustering in C57BL/6J, but not BALB/cJ, litters. There was no association between corpus callosum size and sociability, but smaller brains were associated with lower sociability in BALB/cJ mice. The associations reported here will provide directions for future mechanistic studies of sociability development.

Investigating the effect of the homeopathic immunomodulator, MODUL8® on Blood count, bronchial lavage and fibrin ultrastructure on experimental asthmatic BALB/c mice / Investigación del efecto del inmunomodulador homeopatico Modul8® sobre sangre, lavado bronquial y ultraestructura de la fibrina en ratones experimentales asmáticos BALB/c

Modul8® is a composite mixture of natural products that are known to be an immunomodulator. In the current study the effect of this immunomodulator is tested on an experimental asthmatic BALB/c mouse model to investigate its properties on the white blood cell count in the blood and bronchial lavage of the animals since white blood cells play a fundamental role in the inflammatory process involved in asthma. As it is known that platelets also play an important role in the immune system, the ultrastructure of platelets and fibrin networks were also investigated by scanning electron microscopy. The animals were sensitised, nebulized and treated over a period of 43 days until termination. Results from the blood smears as well as the bronchial lavage smears revealed significantly higher eosinophil counts in the asthmatic group compared to the control and treated groups. Changes in the ultrastructure of the platelets and fibrin networks could also be observed, with the Modul8® -treated group appearing similar to that of the control group where thick major and thin minor fibres could clearly be distinguished and a tight mass of platelet aggregate could be observed. Whereas the fibrin networks from the asthmatic animals appeared flimsy with a tight mass of thin fibres covering the thick major fibres. The asthmatic platelet aggregates appeared granular without the tight round appearance of the control platelet aggregates. It is therefore concluded that Modul8® positively influences the white blood cell counts by altering the asthmatic profile to look similar to that of the control. Also, it seems as if Modul8® has a stabilizing effect on the platelets and fibrin networks. From these results it can be suggested that Modul8® might successfully be used in the treatment of inflammatory conditions such as asthma.

Modul8® es una mezcla compuesta de productos naturales que es conocida por ser un inmunomodulador. En el presente estudio, el efecto de este inmunomodulador se prueba de forma experimental en el modelo de ratón asmáticos BALB/c, para investigar sus propiedades sobre el conteo de glóbulos blancos en la sangre y lavado bronquial de los animales, ya que los glóbulos blancos desempeñan un papel fundamental en el proceso de respuesta inflamatoria implicado en el asma. Como es sabido, también las plaquetas desempeñan un papel importante en el sistema inmunológico, así, la ultraestructura de las plaquetas y las redes de fibrina también fueron investigadas por microscopía electrónica de barrido. Los animales fueron sensibilizados, nebulizados y tratados durante un período de 43 días hasta el término. Los resultados de los frotis de sangre, así como los de lavado bronquial revelaron un número significativamente mayor de eosinófilos en el grupo de asmáticos en comparación con el control y grupos tratados. Cambios en la ultraestructura de las plaquetas y redes de fibrina también pueden ser observados, donde el grupo tratado con la Modul8® aparece similar a el grupo control, donde los fibras de mayor grosor y menor grosor pueden ser claramente distinguidas y además, puede ser observada una apretada masa de plaquetas aglutinadas. Considerando las redes de la fibrina en animales asmáticos parecen endebles con una apretada masa de fibras de menor grosor que cubren las fibras de mayor grosor. Los agregados de plaquetas en asmáticos aparecen granulares sin el aspecto apretado del agregado plaquetario que rodea al grupo control. Por tanto, se concluye que Modul8® positivamente influye en el conteo de glóbulos blancos mediante la alteración del perfil de asmáticos a un aspecto similar al del control. Además, parece como si Modul8® tuviera un efecto estabilizador en las plaquetas y las redes de fibrina. De estos resultados se puede sugerir que Modul8® puede ser utilizado...

Three-dimensional anatomy of the temporal bone in normal mice.

This study was performed to determine the three-dimensional (3D) structure of the murine temporal bone and to provide a survey atlas of the temporal bone structures in mice. The temporal bones of adult BALB/c mice were examined and 3D high-resolution reconstructions of the temporal bone were obtained using a micro-CT system. Using the system described here, the bony labyrinth and membranous labyrinth could be investigated in a non-destructive manner. The turning rate of the cochlea was two (human rate: two and a half). The shapes of the superior and posterior semicircular canals were more flexed than those in humans. The malleus manubrium was directed anteriorly and was thin and fan-shaped like a Persian sword. The size of the incus relative to the malleus was smaller than that in the human ossicles. The 3D reconstruction of murine temporal bone described in this study provides anatomical information that will be useful in future studies using mouse model.

Immunohistochemical characterisation of cell-type specific expression of CK1delta in various tissues of young adult BALB/c mice.

BACKGROUND: Casein kinase 1 delta (CK1delta) phosphorylates many key proteins playing important roles in such biological processes as cell growth, differentiation, apoptosis, circadian rhythm and vesicle transport. Furthermore, deregulation of CK1delta has been linked to neurodegenerative diseases and cancer. In this study, the cell specific distribution of CK1delta in various tissues and organs of young adult BALB/c mice was analysed by immunohistochemistry. METHODOLOGY/PRINCIPAL FINDINGS: Immunohistochemical staining of CK1delta was performed using three different antibodies against CK1delta. A high expression of CK1delta was found in a variety of tissues and organ systems and in several cell types of endodermal, mesodermal and ectodermal origin. CONCLUSIONS: These results give an overview of the cell-type specific expression of CK1delta in different organs under normal conditions. Thus, they provide evidence for possible cell-type specific functions of CK1delta, where CK1delta can interact with and modulate the activity of key regulator proteins by site directed phosphorylation. Furthermore, they provide the basis for future analyses of CK1delta in these tissues.

The corneas of naive mice contain both CD4+ and CD8+ T cells.

PURPOSE: To determine if the corneas of naive mice contain resident CD4+ and CD8+ T cells. METHODS: The presence of T cells in the corneas of naive BALB/c, C57BL/6, and SCID mice was determined by immunostaining with anti-CD4 (clone RM4-5) and anti-CD8 (clone 5H10-1) monoclonal antibodies. Immunostained corneal sections were examined by light microscopy, and immunostained intact corneas were examined by confocal microscopy. The levels of CD4 and CD8 mRNA transcripts in the corneas were determined by TaqMan reverse-transcriptase polymerase chain reaction (RT-PCR) analysis and compared with the expression of these transcripts in the corneas of HSV-1 infected mice. Finally, the number of CD4+ and CD8+ T cells in the cornea of BALB/c, C57BL/6, and ICR mice was determined by cell sorting. RESULTS: Both light microscopic examination of corneal sections and confocal microscopic examination of intact corneas revealed the presence of CD4+ and CD8+ cells in the central and peripheral regions of the corneas of BALB/c and C57BL/6 mice. Stained cells were not detected in corneas of control SCID mice. CD4 and CD8 mRNA transcripts were detected in corneas of BALB/c and C57BL/6 mice while there were markedly lower levels of transcripts in SCID mice. The number of CD4 transcripts was lower than the number of CD8 transcripts in the corneas of both BALB/c and C57BL/6 mice. Finally, cell sorting showed the presence of both CD4+ and CD8+ T cells in corneas of BALB/c, C57BL/6, and ICR mice. CONCLUSIONS: CD4+ and CD8+ T cells are present in corneas of naive C57BL/6, BALB/c, and ICR mice.

Variation in organ volumes of matched BALB/c mice by microcomputed tomography analysis.

High-resolution microcomputed tomography technology has allowed researchers to use live mice to address questions that previously could be answered only at necropsy. Serial analyses of the same mouse allow tissue changes to be followed over time. The ability to follow a single mouse noninvasively can decrease the total number of mice required for the study. The magnitude of inter-mouse variation for matched mice undergoing microcomputed tomography has not been determined previously. We selected lung and contrast-enhanced stomach as tissues of standard size and anatomical structure that were hypothesized to vary minimally between mice. The analyses of the tissue volumes from matched mice showed considerable variation among mice, among multiple sequential scans of the same mouse, and even among multiple evaluations of the same scan. More variation occurred with repeated scans of the same mouse (intramouse variation) than between mice (intermouse variation). In addition, significant variation and obvious bias was detected between the 2 scan evaluators. These data suggest that to obtain the widest range of possible values, among which the true value would be found, multiple analyses of multiple scans of the same mouse must be performed by multiple scan evaluators.

Anatomy and nomenclature of murine lymph nodes: Descriptive study and nomenclatory standardization in BALB/cAnNCrl mice.

Murine lymph nodes are intensively studied but often assigned incorrectly in scientific papers. In BALB/cAnNCrl mice, we characterized a total of 22 different lymph nodes. Peripheral nodes were situated in the head and neck region (mandibular, accessory mandibular, superficial parotid, cranial deep cervical nodes), and at the forelimb (proper axillary, accessory axillary nodes) and hindlimb (subiliac, sciatic, popliteal nodes). Intrathoracic lymph nodes included the cranial mediastinal, tracheobronchal and caudal mediastinal nodes. Abdominal lymph nodes were associated with the gastrointestinal tract (gastric, pancreaticoduodenal, jejunal, colic, caudal mesenteric nodes) or were located along the major intra-abdominal blood vessels (renal, lumbar aortic, lateral iliac, medial iliac and external iliac nodes). Comparative and nomenclative aspects of murine lymph nodes are discussed. The position of the lymph nodes of BALB/cAnNCrl mice is summarized and illustrated in an anatomical chart containing proposals for both an official nomenclature according to the Nomina Anatomica Veterinaria and English terms.

The regional distribution and relative frequency of gastrointestinal endocrine cells in the nude mice, Balb/c-nu/nu: an immunohistochemical study.

The distributions and frequencies of some endocrine cells in the eight portions of the gastrointestinal (GI) tract - fundus, pylorus, duodenum, jejunum, ileum, cecum, colon and rectum of the nude mouse, Balb/c-nu/nu were studied with immunohistochemical method using six types of anti-sera against serotonin, gastrin, cholecystokinin (CCK)-8, somatostatin, glucagon and human pancreatic polypeptide (hPP). All of six types of immunoreactive (IR) cells were identified. Most of IR cells in the intestinal portion were generally spherical or spindle in shape (open type cell) while cells showing round in shape (close type cell) were found in the intestinal gland and stomach regions occasionally. Their relative frequencies were varied according to each portion of GI tract. Serotonin-IR cells were detected throughout the whole GI tract and they showed the highest frequency in the pylorus. Gastrin-IR cells were restricted to the pylorus and duodenum with numerous and a few frequencies, respectively. CCK-8-IR cells were also restricted to the pylorus, duodenum and jejunum with numerous, a few and rare frequencies, respectively. Somatostatin-IR cells were demonstrated throughout the whole GI tract except for the colon and rectum, and they showed the highest frequency in the fundus. In addition, glucagon- and hPP-IR cells were restricted to the fundus and rectum, respectively with a few frequencies. In conclusion, the general distribution patterns and relative frequency of GI endocrine cells of the nude mouse, Balb/c-nu/nu was similar to that of other strains of mice. However, some strain and/or species-dependent unique distributions and frequencies of endocrine cells were also observed especially for somatostatin- and hPP-IR cells.

An immunohistochemical study of gastrointestinal endocrine cells in the BALB/c mouse.

The distributions and frequencies of some endocrine cells in the eight portions of the gastrointestinal tract (GIT) of BALB/c mouse were studied. Endocrine cells were stained using immunohistochemical method with seven types of antisera against bovine chromogranin (BCG), serotonin, gastrin, cholecystokinin (CCK)-8, somatostatin, glucagon and human pancreatic polypeptide (HPP), and the regional distributions and their relative frequencies were observed in the eight portions of the GIT of BALB/c mice. All seven types of immunoreactive (IR) cells were identified. Most of the IR cells in the intestinal portion were generally spherical or spindle in shape (open type cell) while round-shaped cells (closed type cell) were found in the intestinal gland and stomach regions occasionally. Their relative frequencies varied according to each portion of the GIT. BCG-IR cells were observed throughout the whole GIT except for the rectum and they were most predominant in the pylorus. Serotonin-IR cells were detected throughout the whole GIT and they showed the highest frequency in the fundus. Gastrin- and CCK-IR cells were restricted to the pylorus and duodenum with a majority in the pylorus and rare or a few frequencies in the duodenum. Compared with other mammals, somatostatin-IR cells were restricted to the fundus and pylorus with a few frequencies, respectively. In addition, glucagon- and HPP-IR cells were restricted to the fundus and duodenum, respectively, with relative low frequencies. Some species-dependent unique distributions and frequencies of endocrine cells were observed in the GIT of BALB/c mouse compared with other rodents.

Morphofunctional characteristic of mast cells in BALB/c and C57Bl/6 mice during cold exposure.

Mast cells of the mesentery and subcutaneous tissue in BALB/c and C57Bl/6 mice were studied after single and repeated cold exposure (-20 degrees C, 3 min). Immediate adaptive reactions of mast cells in BALB/c and C57Bl/6 mice did not differ after single cold exposure and were manifested in increased degranulation. Repeated cold exposure of BALB/c mice was followed by an adaptive reaction, which included an increase in the count of mast cells in subcutaneous tissue and normalization of the degranulation index. In C57Bl/6 mice the count of mast cells in subcutaneous tissue decreased, while the degranulation index remained high. These changes reflect the disadaptive response of mast cells to repeated cold exposure.

Alteraçoes ósseas na leishmaniose cutânea difusa (LCD) no Estado do Maranhão: aspectos clínicos, de imagens e histopatológico / Bone changes in cutaneous diffuse leishmaniasis (CDL) in the Maranhão state: clinical, imaging and histopathological aspects

Estudo das alterações ósseas na leishmaniose cutânea difusa (LCD) e associação com Leishmania (Leishmania) amazonensis em oito pacientes do Estado do Maranhão. Foram realizados exames de imagens, histopatológico do tecido ósseo e estudo experimental utilizando Leishmania e camundongos BALB/c. O estudo mostrou deformidades nas extremidades distais dos membros superiores e inferiores, limitação funcional, associação com lesões cutâneas e processos inflamatórios múltiplos. A histopatologia mostrou osteomielite crônica por Leishmania. O modelo experimental confirmou a infecção óssea crônica. Propõe-se a inclusão do protozoário como agente etiológico de osteomielite crônica.../Study of bone changes in Diffuse Cutaneous Leishmaniasis (DCL) and association with Leishmania (Leishmania) amazonensis in eight patients from Maranhão state. Imaging, histopathology exams of the bone tissue and experimental study using Leishmania and BALB/c mice were done. The studies showed deformity of extremities of upper and lower extremities, functional limitation, association with cutaneous lesions and multiple inflammations. The histopathology showed chronic osteomyelitis by Leishmania. The experimental model confirmed the bone chronic inflammation. We propose the inclusion of the protozoan as cause of chronic osteomyelitis

Distribution of the vanilloid receptor (VR1) in the gastrointestinal tract.

The gastrointestinal (GI) tract responds to a variety of stimuli through local and centrally mediated pathways. Changes in the intestinal microenvironment are sensed by vagal, spinal, and intrinsic primary afferent fibers. Sensory nerve endings located close to the lumen of the GI tract respond to pH, chemical composition of lumenal contents, or distortion of the mucosa. Afferents within the muscle layers are thought to be tension sensitive, whereas those located within the myenteric plexus are also thought to respond to changes in chemical composition and humoral substances. Subpopulations of these afferent fibers are activated by capsaicin. However, the exact location of these nerves is currently not known. The vanilloid receptor (VR1) is a nonselective cation channel that is activated by capsaicin, acid, and temperature. Antibodies to VR1 make it possible to determine the location of these afferents, their morphology, and their relationships with enteric nerves and other cell types in the GI tract. VR1-like immunoreactivity was observed on nerves within myenteric ganglia and interganglionic fiber tracts throughout the GI tract. VR1 nerves were also observed within the muscle layers and had an irregular profile, with varicose-like swellings along their lengths. Blood vessels within the GI wall had VR1-immunoreactive nerve fibers associated with them. VR1-like nerves and other immunopositive cells were also observed within the mucosa. In summary, VR1-like immunoreactivity was found in several locations within the GI tract and may provide sensory integration of chemical, physical, or inflammatory stimuli. VR1-like fibers appear to be predominantly spinal in origin, but a few vagal VR1-like fibers exist in the stomach.

Marked differences in olfactory sensitivity and apparent speed of forebrain neuroblast migration in three inbred strains of mice.

In the adult forebrain, new neuroblasts constantly migrate from the subventricular zone along the rostral migratory stream to the olfactory bulb, where many become neurons. It is unclear whether this process is different in commonly used mouse strains and whether it is related to olfactory function. Adult male BALB/c, C57BL/6, and 129/S1 (formerly 129SV) mice were tested for olfactory sensitivity plus discrimination, using male mouse urine from the two other strains. BALB/c mice had the greatest olfactory sensitivity, followed by 129/S1, and C57BL/6 mice, by an order of magnitude each. Newly formed cells were pulse-labeled for 3 h with i.p. 5-bromo-2'-deoxyuridine (BrdU) injections and the animals analyzed 24 h later. In 129/S1 mice, a greater proportion of neuroblasts were present closer to the olfactory bulb than in BALB/c mice, followed by C57BL/6 mice. The total number of BrdU-labeled cells did not differ, suggesting differences in migration and not proliferation. The impaired olfactory function in C57BL/6 mice might be caused by the reduced number of neuroblasts that reach the olfactory bulbs. However, olfactory function in BALB/c and 129/S1 mice did not correlate with their putative migration speed, suggesting a more complex nature of cellular processes that contribute to olfactory function. These results caution against comparing studies of olfactory function or neural precursors that use different strains of mice, and question the use of C57BL/6 mice as a "normal" strain or as transgenic background. Perhaps more importantly, the results point to an opportunity to identify genes that regulate olfactory function and neuroblast behavior.

Embryonic origin of the caudal mesenteric artery in the mouse.

It is commonly held that the caudal mesenteric artery (CaMA, or inferior mesenteric artery in humans) arises in the same manner as the celiac and cranial mesenteric artery (CrMA, or superior mesenteric artery in humans), i.e., from the remodeling of the vitelline system of arteries that surrounds and supports the yolk sac. Conflicting evidence about the precise manner in which the CaMA arises was presented in studies of the luxate syndrome (Carter: J. Genet. 1954;52:1-35) and sirenomelia (Schreiner and Hoornbeek: J. Morphol. 1973;141:345-358) in the mouse. These studies suggested that the CaMA arises from the remodeling of the medial umbilical arterial roots. Later studies of blood vessel development in the hindlimb of the Dominant hemimelic mouse (Gest: Anat. Rec. 1984;208:296; Anat. Rec. 1987;218:49A; Gest and Roden: Anat. Rec. 1988;220:37-38A) also supported the results of the previous studies. The present investigation tests the hypothesis that the CaMA arises as a result of the regression and remodeling of the medial umbilical arterial roots. Vascular corrosion casts of 9.5-13.5-day-old mouse embryos were observed by scanning electron microscopy (SEM). The results of the present investigation agree with the aforementioned studies. The medial umbilical roots initially conduct the blood to the placenta. On days 10-12 the medial umbilical roots regress and remodel into the CaMA, while the lateral umbilical roots take over the blood supply to the placenta. On the basis of our results, we conclude that the CaMA arises from the medial umbilical roots and not from the remodeling of the vitelline system of arteries, as previously assumed.