Electric activity in the neocortex of freely moving young and aged rats

Electroencephalographic activity of the neocortex was evaluated in young (5-7 months) and aged (26-28 months) rats. All animals in the aged group showed behavioral impairment in a spatial task (water maze). A neocortical electroencephalogram was derived simultaneously from 16 different neocortical locations and was subjected to spectral analysis. The frequency of occurrence and duration of high-voltage spindles was determined in two sessions, each involving a total of 30 min alert immobility. Changes in spectral characteristics and high-voltage spindles in response to scopolamine administration were also evaluated. The power of high-frequency activity (8-20 Hz) was significantly reduced in the aged subjects. This was greatest in the temporo-occipital regions, while no significant changes were seen in the mediofrontal region. Scopolamine resulted in a large power increase in all frequency bands, but the increase in the higher-frequency range (8-20 Hz) was significantly less in the aged group. The incidence of high-voltage spindles was 6 times higher and their total duration was 9 times longer in aged rats, with virtually no overlap with the young group. In young rats, scopolamine increased the incidence and total duration of high-voltage spindles, while it decreased both parameters in the aged subjects. Cholinergic neurons in the nucleus basalis appeared shrunken in the aged animals. These findings demonstrate that reliable electroencephalographic changes are present in the neocortex of the aged rat, and that some of the physiological alterations may be due to the pathological changes in the cholinergic nucleus basalis.     

The expression patterns of mRNA-encoding stem cell factor, internal stem cell factor and c-kit in the prepubertal and adult porcine ovary

The receptor, c-kit, and its ligand, stem cell factor (SCF), are important regulators of ovarian follicle growth and development. The aim of this study was to identify the sites of expression of mRNA for c-kit and SCF in prepubertal and mature (pregnant and non-pregnant) animals. Ovaries were recovered from prepubertal animals, non-pregnant sows and five sows at approximately 3 months of gestation. Ovine SCF and c-kit DNA were cloned into plasmid vectors to produce RNA probes. Expression of mRNA encoding SCF and c-kit were detected via in situ hybridization. Both mRNA were detected throughout ovaries from all animals. This study provides evidence that the growth-factor complex is required throughout follicle development, and also for continued maintenance of the corpus luteum (CL) in the mature animal. SCF mRNA was localized to the granulosa cell layer and was also extensively expressed in endothelial tissue and throughout the CL. c-kit mRNA was detected in the theca layer, oocytes and also in CL. In conclusion, expression of SCF and c-kit mRNA in granulosa and theca cells, respectively, indicate an important interaction between somatic cells throughout follicle development and that in the mature animal, SCF and c-kit potentially have a role in maintaining progesterone secretion by the CL. The observations of continued expression of SCF and c-kit throughout development suggest that there may be differences in the role of this receptor-ligand complex between large mono- vs. poly ovulatory species, such as the pig.     

Acquired functional asplenia in sarcoidosis

Sarcoidosis is a recently identified cause of functional asplenia that can be diagnosed by radionuclide imaging. A 31-year-old woman with a five-year history of histologically compatible sarcoidosis was found to have nonvisualization of the spleen on technetium 99m sulfur colloid (radiopharmaceutical) liver-spleen scan. This scintigraphic finding was accompanied by poikilocytosis and Howell-Jolly bodies in the peripheral blood smear. A subsequent gallium 67 citrate scan reflected an abnormal increase in concentration of activity in the spleen, suggesting an active inflammatory process.     

Mycobacterium haemophilum: microbiology and expanding clinical and geographic spectra of disease in humans.

Reports of the association of Mycobacterium haemophilum with disease in humans have greatly increased. At least 64 cases have now been reported, with symptoms ranging from focal lesions to widespread, systemic disease. The organism is now known to cause primarily cutaneous and subcutaneous infection, septic arthritis, osteomyelitis, and pneumonitis in patients who are immunologically compromised and lymphadenitis in apparently immunocompetent children. Underlying conditions in the compromised patients have included AIDS; renal, bone marrow, and cardiac transplantation; lymphoma; rheumatoid arthritis; marrow hypoplasia; and Crohn's disease. Reports have originated from diverse geographic areas worldwide. The epidemiology of M. haemophilum remains poorly defined; there appears to be a genetic diversity between strains isolated from different regions. The organism is probably present in the environment, but recovery by sampling has not been successful. M. haemophilum has several unique traits, including predilection for lower temperatures (30 to 32 degrees C) and requirement for iron supplementation (ferric ammonium citrate or hemin). These may in the past have compromised recovery in the laboratory. Therapy has not been well elucidated, and the outcome appears to be influenced by the patient's underlying immunosuppression. The organisms are most susceptible to ciprofloxacin, clarithromycin, rifabutin, and rifampin. Timely diagnosis and therapy require communication between clinician and the laboratory.     

Evaluation of two immunofluorescence assays with monoclonal antibodies for typing of herpes simplex virus.

An indirect immunofluorescence assay and a direct immunofluorescence assay were evaluated for typing clinical isolates of herpes simplex virus (HSV). The indirect immunofluorescence assay (Electro-Nucleonics, Inc.) correctly identified 16 HSV type 2 (HSV-2) isolates, but failed to identify 4 of 14 HSV-1 isolates because of background fluorescence and instability of reagents. Forty-nine HSV-1 isolates were correctly typed by direct immunofluorescence assay (Kallestad Laboratories, Inc.), but 1 of 39 HSV-2 isolates did not react with the HSV-2 type-specific antibody conjugate.     

A strain gauge device for measuring feeding or drinking in laboratory rats

The details of mechanical construction and electronic circuitry of a strain gauge system for continuously measuring food and water ingestion in laboratory rats are described. The system has been reliably tested over a number of years. It is eminently suitable for investigating daily rhythms in rat feeding and drinking behavior, where a large volume of data is collected over extended periods of time.     

Comparison of ethanol versus formalin fixation on preservation of histology and RNA in laser capture microdissected brain tissues

Although RNA can be retrieved from formalin-fixed, paraffin-embedded (FFPE) tissues, the yield is low, and the RNA is fragmented. Recent advances in gene expression profiling underscore the importance of identifying a fixative that preserves histology and mRNA. We demonstrated that, for immersion fixation of brains, 70% ethanol is superior to formalin for mRNA preservation. RNA yield from ethanol-fixed tissues was 70% of the yield from fresh frozen specimens, but only a negligible quantity was recovered from formalin-fixed tissues. RNA from ethanol-fixed brains showed integrity comparable to RNA from fresh frozen tissues, and RT-PCR using RNA from ethanol-fixed tissues was consistently successful. RNA from FFPE tissues composed of low-molecular weight fragments, and their use in RT-PCR failed repeatedly. The yield and quality of RNA from ethanol-fixed brains were unaffected after immersion at 4 degrees C for 2 weeks. In a blinded comparison to FFPE tissues, ethanol-fixed specimens were judged to show comparable histology and superior immunostaining. After laser capture microdissection (LCM), we failed to recover mRNA from FFPE tissues but retrieved mRNA from ethanol-fixed tissues for RT-PCR and cDNA microarray analysis. We conclude that 70% ethanol preserves RNA integrity and is suitable for expression profiling of brain tissues by LCM and cDNA microarray.     

The detection of antibodies against foot-and-mouth disease virus (FMDV) in filter paper eluates from pig sera or whole blood by ELISA.

The use of pig blood samples dried on paper discs for the detection of antibodies against FMDV by the liquid phase blocking ELISA has been evaluated. The average volume of whole heparinised blood required to fully saturate 6.0 mm discs was 7.65 microliters (range 7.2 to 8.1; variation = 0.24, P = 0.05). When 200 clinically healthy animals were assessed by virus neutralisation (VN) titres up to 1/22 were recorded against types O, A and C, 97% being 1/11 or less. Using ELISA, results were more skewed. Overall, 91% showed titres of 1/32 or less, and there were occasional high non-specific reactors with types O and A. Using small groups of sera from experimental animals, a VN titre of 1/16 was found to be equivalent to an ELISA titre of approximately 1/100 (log10 2.0 +/- 0.2) with type O and 1/56 (log10 1.75 +/- 0.1) for type A. Although some loss in sensitivity from disc dried sera was found in selected negatives on testing at a single dilution of 1/32, sera from vaccinated animals with VN titres of 1/16 to 1/708 all gave strong positive results. A monoclonal antibody (Mab) assay was successfully developed to detect different swine anti-FMDV antibody isotypes.     

Disease-specific electrophysiological findings in adult ceroid-lipofuscinosis (Kufs disease)

Two adults with mild dementia and a history of memory loss and disequilibrium were seen in the eye clinic following complaints of acuity loss in the 20/30–20/70 (Snellen) range. Results from the fundus examination of one patient were entirely normal; the other showed minimal vascular attenuation and optic atrophy. Electrophysiology was remarkable: (1) Photopic ERG b-waves were reduced, delayed, and showed pronounced oscillations. (2) EOG light-rise potentials were absent or very small. (3) Binocular pattern-VER signals showed addition of the monocular signal. Scotopic ERG signals were normal. Brain biopsy and microscopy showed intercellular, autofluorescent ceroid deposits which provided a clear diagnosis of Kufs disease. Histology of model animal retinal cells show ceroid deposits in cell classes implicated by the human retinal signals. The cluster of electrophysiological results point toward early changes in the pigment epithelium and inner plexiform layer cells as a means of non-invasive diagnosis.     

The effects of diazepam on "fear" reactions in rats are modulated by environmental constraints on the rat's defensive repertoire

The simultaneous effects of diazepam on three shock-induced reactions in rats were studied in order to determine the reliability of these behaviors as indices of anxiolytic drug action. Rats were injected with 1 mg/kg of diazepam or vehicle, placed in a 2-compartment chamber containing bedding material, and shocked with 1, 2, or 6 mA when they first touched a wire-wrapped prod attached to one end of the chamber. Diazepam-treated animals displayed significantly less burying behavior, but paradoxically, they also displayed more passive avoidance behavior and fewer exploratory side-transitions than vehicle-injected controls. Defensive burying behavior tended to be negatively correlated with passive avoidance behavior and positively correlated with exploratory side transitions. When the "competitive" relationship between defensive burying and passive avoidance was eliminated by testing rats in a 2-compartment chamber not containing bedding material, diazepam produced a significant suppression of passive avoidance and a significant increase in exploratory side-transitions, compared to control. Taken together, these results suggested that the validity of any single behavioral model of anxiolytic drug action might vary as a function of environmental constraints on the subjects' defensive repertoire.