Efficacy of recombinant bovine interleukin-2 as an adjunct to dry cow therapy

Recombinant bovine interleukin-2 was tested as adjunct therapy to intramammary infusion of antibiotics at drying off. Cows were assigned randomly within three commercial herds to either recombinant bovine interleukin-2 or PBS treatment groups at drying off. Ninety-five cows received intramammary infusions of 1 mg of recombinant bovine interleukin-2 in each quarter immediately preceding intramammary infusion of a product for antibiotic therapy of dry cows. Ninety-four cows received intramammary infusion of 10 ml of endotoxin-free PBS in each quarter immediately preceding the antibiotic therapy. Cure rates for IMI present at drying off did not differ between cows treated with recombinant bovine interleukin-2 and those treated with PBS. Intramammary infusion of recombinant bovine interleukin-2 did not affect the rate of new IMI during the dry period. Milk production and SCC during the first 3 mo of lactation subsequent to therapy did not differ between treatment groups. Intramammary infusion of recombinant bovine interleukin-2 was not effective as an adjunct to antibiotic therapy for dry cows.

Tetanus toxin-induced seizures in infant rats and their effects on hippocampal excitability in adulthood

A new experimental model of developmental epilepsy is reported. Behavioral and EEG features of seizures produced by unilateral intrahippocampal injection of tetanus toxin in postnatal day 9-11 rats, are described. Within 24-72 h of tetanus toxin injection, rat pups developed frequent and often prolonged seizures which included combinations of repetitive wet dog shakes, and wild running-jumping seizures. Intrahippocampal and cortical surface EEG recordings showed that coincident with these behaviors, electrographic seizures occurred not only in the injected hippocampus, but also in the contralateral hippocampus and bilaterally in the neocortex. Analysis of the interictal EEG revealed multiple independent spike foci. One week following tetanus toxin injection, the number of seizures markedly decreased; however, interictal spiking persisted. After injection rats were allowed to mature some were observed to have unprovoked behavioral seizures and/or epileptiform EEG activity. Mature animals were also studied using in vitro slice techniques. Recordings from hippocampal slices demonstrated spontaneous epileptiform burst discharges in the majority of rats which had tetanus toxin induced seizures as infants. These events occurred in area CA3 and consisted of interictal spikes and intracellularly recorded paroxysmal depolarization shifts (PDSs). On rarer occasions, electrographic seizures were recorded. The use of the tetanus toxin model in developing rats may facilitate a better understanding of the unique features of epileptogenesis in the developing brain and the consequences early-life seizures have on brain maturation and the genesis of epileptic conditions in later life.

Development of a PCR amplification assay as a screening test using bulk milk samples for identifying dairy herds infected with bovine viral diarrhea virus

The approach of cDNA synthesis followed by polymerase chain reaction (PCR) amplification was used to develop a rapid screening test for the detection of bovine viral diarrhea virus (BVDV) in bulk tank milk samples. The initial development of this detection method was done using lactating Holstein cows; 1 acutely infected with BVDV following experimental inoculation and 2 persistently infected (PI) with BVDV. Viral RNA was extracted from somatic cells purified from whole milk using a guanidinium isothiocyanate and phenol/chloroform extraction method. Oligonucleotide primers were selected from the 5'untranslated region (5'UTR) and p80 region of BVDV genome. In the acutely infected cow, BVDV RNA was identified from days 6 to 10 postinoculation. Viral RNA extracted from somatic cells of milk from PI cows was detected by PCR using both 5'UTR and p80 primer sets. The sensitivity of PCR detection was determined by preparing dilutions of whole milk obtained from the BVDV persistently infected animals with milk from a BVDV-negative cow followed by purification of somatic cells and RNA extraction. BVDV was detected in milk serially diluted to 1:640 using PCR amplification. In addition, PCR amplification was 14.6 times more sensitive than virus isolation in detecting BVDV RNA in purified milk somatic cells. PCR detected BVDV RNA from a minimum of 580 somatic cells while the detection limit of virus isolation was 8500 cells. The sensitivity and specificity of BVDV amplification were confirmed by Southern hybridization analysis. BVDV RNA was detected using PCR in 33 out of 136 bulk milk samples collected from 124 individual herds using the 5'UTR primer set. These results indicate that PCR analysis of bulk tank milk samples may provide a rapid and sensitive method of screening herds for the presence of BVDV infections.

Effects of an Escherichia coli J5 vaccine on mild clinical coliform mastitis

Efficacy of an Escherichia coli (O111:B4) J5 bacterin was tested in an experimental challenge trial. Nineteen cows were vaccinated with an E. coli J5 bacterin, and 10 cows were injected with a placebo containing adjuvant only. Vaccine and placebo were administered at drying off, 30 d after drying off, and within 48 h after calving. Cows were challenged approximately 30 d after calving by intramammary infusion with a smooth heterologous strain of E. coli previously shown to cause mild clinical mastitis. Vaccination with the J5 bacterin reduced duration of IMI and local signs of clinical mastitis. Concentrations of BSA in milk 24 h after challenge were greater in control cows than in cows vaccinated with J5. The SCC at 7 d postchallenge were greater for cows vaccinated with the placebo than for cows vaccinated with J5. Bacterial counts were lower for cows vaccinated with the placebo than for cows vaccinated with J5 at 3, 6, and 9 h postchallenge. In contrast, cows vaccinated with J5 had lower bacterial counts at 2, 3, and 4 d postchallenge than did cows vaccinated with placebo. Systemic signs of clinical mastitis were relatively mild and similar between treatment groups. Rectal temperature, DMI, and milk production did not differ between control and cows vaccinated with J5 following challenge.

Efficacy of dry cow therapy and a Propionibacterium acnes product in herds with low somatic cell count

Dry cow therapy and a Propionibaterium acnes product were evaluated in four commercial herds with low SCC. Cows were randomly assigned within herds to treatment groups of approximately 90 cows receiving dry cow therapy, P. acnes, dry cow therapy plus P. acnes, or no treatment in a factorial arrangement. Each lactating quarter of cows that received dry cow therapy was infused via the teat duct with 300 mg of cephaprin at drying off. Cows that received P. acnes were infused intravenously with .4 mg of killed P. acnes at drying off, 7 to 10 d prepartum, and within 7 d after calving. A second prepartum injection of P. acnes immunostimulator was administered to cows that did not calve within 10 d after the first prepartum injection. Dry cow therapy enhanced bacteriological cures of IMI by Staphylococcus aureus and Corynebacterium bovis at drying off. Dry cow therapy reduced incidence of new IMI by environmental streptococci and C. bovis that originated during the dry period. Cows treated with P. acnes alone had a greater incidence of new IMI by Gram-negative bacilli originating during the dry period than did cows in the other treatment groups. Incidence of clinical mastitis at calving was greater for cows receiving no treatment than for cows receiving dry cow therapy, P. acnes, or dry cow therapy plus P. acnes.

Localizing sites of intradendritic electrophysiological recordings by confocal light microscopy

Studies were undertaken to develop microscopic methods and imaging procedures that would permit identification of sites of intradendritic microelectrode recordings from pyramidal cells in hippocampal slice preparations. Intradendritic recordings were obtained with sharp microelectrodes filled with the dye lucifer yellow. Following a recording session a neuron was iontophoretically injected with the dye and imaged by fluorescence videomicroscopy. Images were stored on videotape for later analysis. They provided a record of the location of the microelectrode recording site. After withdrawal of the microelectrode, slices were processed histologically and imaged a second time with a Bio-Rad 600 confocal attachment on an Olympus BH-2 microscope. Confocal images provided detailed anatomical information in three dimensions. In most instances, a clear identification of the recording site was achieved by comparing video images containing the recording electrode and confocal images. Neurophysiological recordings obtained from proximal and distal apical dendrites were markedly different. Proximal dendritic recordings were similar to those obtained from pyramidal cell soma. However, distal dendrites were not electroresponsive when depolarized by intracellular current injection. The techniques described here, or variations that employ patch electrodes, could provide valuable information that should further an understanding of the properties of dendrites in the central nervous system.

Effect of joint position and ligament tension on the MR signal intensity of the cruciate ligaments of the knee

Six cadaveric lower extremities were imaged with T1-weighted spin-echo pulse sequences with the knees extended and flexed to 90 degrees. Magnetic resonance signal intensities of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) were compared. Changing from extension to flexion resulted in decreased signal intensity in six of six ACLs and five of six PCLs. Two of the knees were then imaged with and without tension applied to the ACL. Both specimens showed a decrease in signal intensity with tension, followed by an increase in signal intensity with release of the tension. Finally, in three of the limbs the ACL was surgically reconstructed and then imaged with and without tension applied to the tendon graft. Signal intensity decreased with tension and increased with release of the tension in all three specimens. Thus, joint position and changes in ligament tension affect the signal intensity of the ACL and PCL, generally resulting in a signal intensity decrease with tension.

Plaster of Paris splintage for the hand: volar or dorsal?

The effectiveness of a volar or a dorsal plaster of Paris slab for splinting a hand in the 'safe' position was studied prospectively. Seventy-two splints, comprising 36 dorsal and 36 volar, were applied. Measurements of the metarcarpophalangeal joint angle and the proximal interphalangeal joint angle on the lateral radiograph revealed the volar splint to be significantly more consistent in securing the proximal interphalangeal joint angle at less than 15 degrees. There was no significant difference between volar or dorsal splints for the metarcarpophalangeal joint angle. As the volar splint was also subjectively more comfortable, its use is recommended.

Effect of dietary fat and vitamin E on alpha-tocopherol and beta-carotene in blood of peripartum cows

Nonlactating cows were fed diets containing 88% grass forage and 12% concentrate (DM basis). Starting 14 d prior to anticipated calving, the concentrate was changed to provide 0 or 200 g of supplemental fat and 0 or 890 IU of supplemental vitamin E daily. Following parturition, cows were fed for 14 d a 50% concentrate diet that provided the same amounts of supplemental fat and vitamin E that were fed during the dry period. Plasma was sampled and analyzed for alpha-tocopherol and beta-carotene. Supplemental dietary fat elevated plasma concentrations of both nutrients during the peripartum period. Supplemental dietary vitamin E elevated concentrations of alpha-tocopherol during that period. Dietary fat also increased concentrations of plasma cholesterol. When alpha-tocopherol and beta-carotene were expressed per unit of plasma cholesterol, fat supplementation did not affect concentrations. Dietary treatments did not influence concentrations of alpha-tocopherol in blood neutrophils and did not affect intracellular kill of bacteria by neutrophils. Essentially no beta-carotene was found in the neutrophils. For colostrum, dietary vitamin E increased concentrations of alpha-tocopherol and decreased concentrations of beta-carotene.

c-erbB-2 amplification in breast cancer: detection in formalin-fixed, paraffin-embedded tissue by in situ hybridization

We describe a sensitive and practical in situ hybridization method, using a digoxigenin-labeled probe, for the detection of c-erbB-2 amplification in breast cancer in formalin-fixed, paraffin-embedded tissue sections. Forty-six primary breast carcinomas were studied. Nuclear hybridization signal was observed in 36 of 46 carcinomas. Signal was confined to malignant cells. Normal breast epithelium and stromal and inflammatory cells were uniformally negative. DNase predigestion, no-probe preparations, and competitive hybridization confirmed the specificity of the reaction. The hybridization reaction was localized to multiple discrete foci in tumor cell nuclei, suggesting multiple sites of gene copy and transcriptional activity in the nucleus. Considerable cell-to-cell variation in hybridization signal was evident within individual tumors and positive reactions were observed in several cases in which amplification could not be detected by either Southern or slot blot analysis. The high sensitivity and specificity of the reaction and its use in a tissue-based system will allow the study of a range of possible precursor lesions of breast cancer for evidence of c-erbB-2 amplification.

Therapy of experimentally induced coliform mastitis with a Propionibacterium acnes product

The efficacy of a Propionibacterium acnes product for treatment of coliform mastitis was evaluated following intramammary infusion of Escherichia coli. Ten cows were injected intravenously with a product containing heat-killed P. acnes at 3 h, 3 d, and 7 d after bacterial challenge. Five cows served as untreated negative controls. Bacterial counts in milk, rectal temperatures, and milk SCC did not differ between treated cows and control cows. Intravenous infusion of P. acnes had no effect on milk production or DMI of treated cows compared with untreated controls. Therapy of experimentally induced coliform mastitis with a P. acnes product had no effect on severity or duration of clinical signs.

What's new in breast cancer? Molecular perspectives of cancer development and the role of the oncogene c-erbB-2 in prognosis and disease

The oncogene c-erbB-2 is frequently amplified in human breast carcinoma. The c-erbB-2 gene is present as a single copy in normal cells, and has been mapped to chromosome 17 in the region 17q 12-21.32. c-erbB-2 encodes a transmembrane glycoprotein known as p185. The intracellular component of p185 has tyrosine kinase activity; the extracellular domain has a structure resembling a growth factor receptor. c-erbB-2 amplification, p185 overexpression and levels of transcribed c-erbB-2 specific messenger RNA have been studied in a large number of breast carcinomas using a variety of techniques. In general, overexpression of p185 oncoprotein reflects various levels of DNA amplification, though in some cases amplification can be detected in the absence of overexpression of p185 and similarly overexpression of p185 can be present without detectable levels of c-erbB-2 amplification. This findings suggests that multiple mechanisms may be responsible for overexpression. c-erbB-2 amplification and/or overexpression occurs in almost all cases of high grade duct carcinoma in-situ, but has been reported in only 10%-40% of infiltrating duct carcinoma. c-erbB-2 amplification or overexpression occurs rarely in invasive lobular carcinoma, and has not been detected in ductal or lobular epithelial hyperplasia, or in atypical ductal or atypical lobular hyperplasia. It is generally believed that c-erbB-2 amplification/overexpression is an important independent prognostic indicator in breast carcinoma, identifying a subset of patients with poor prognosis tumours, particularly if axillary node metasases are present. However, many unanswered questions remain regarding c-erbB-2 and its role in breast cancer development and progression. The causes of c-erbB-2 amplification are unknown. There is no evidence of mutations in the human gene which might cause amplification or overexpression. The significance of the differences in levels of c-erbB-2 amplification/overexpression in in-situ duct carcinoma and associated invasive duct carcinoma has not been established. Amplification or overexpression have not been reported in atypical duct hyperplasia, a proposed precursor of duct carcinoma in-situ, yet overexpression occurs almost always in high grade duct carcinoma in-situ. c-erbB-2 may play a critical role in the development of a clonal in-situ, proliferation of high histological grade, yet does not obviously influence the acquisition of an invasive phenotype. We would postulated that this instability in amplification/overexpression is of biological significance, and if better understood may aid in the study of progression of human breast carcinoma.

Environmental mastitis

Environmental mastitis affects all dairy farms and generally is the major mastitis problem on modern, well managed dairy farms. Control measures effective against contagious pathogens are of little value in controlling of environmental pathogens. Control of environmental mastitis is achieved by reducing exposure of teat ends to environmental pathogens and by maximizing the resistance of the cow to intramammary infection. Significant sources of environmental pathogens are organic bedding materials, manure covered alleyways, and wet or damp areas in barns, exercise lots, or pastures. Milking time hygiene can influence teat-end exposure. In general, exposure is minimized when all areas of the environment are clean, cool, and dry. Resistance is maximized by providing a stress-free environment that minimizes teat-end injury, and by feeding balanced diets sufficient in vitamin E and selenium. Antibiotic therapy during lactation or the dry period is of little value in the control of environmental mastitis in dairy herds, with the exception of preventing environmental streptococcal infection during the early dry period. Effective vaccines may help reduce the impact of environmental mastitis in the near future.

Localized excitatory synaptic interactions mediate the sustained depolarization of electrographic seizures in developing hippocampus

Repetitive synchronized neuronal discharging that lasts for seconds and even minutes in in vitro brain slice preparations are important new models in experimental epilepsy. In hippocampal slices from 1-2-week-old rats, individual CA3 pyramidal cells undergo a sustained depolarization during such electrographic seizures, induced by GABAA receptor antagonists. In experiments reported here these events were produced in small isolated segments of the CA3 subfield, measuring only 400-500 microns along the cell body layer. In such minisclices local application of either kynurenic acid or 6-cyano-7-nitroquinoxaline-2-3-dione (CNQX) to the proximal basilar dendrites abolished the synchronized discharges of electrographic seizures. Interictal spikes appeared unaffected by this treatment. Application of these excitatory amino acid receptor antagonists to distal basilar dendrites or apical dendrites was ineffective. In "larger" minislices, measuring 700-1000 microns along the cell body layer, application of kynurenic acid, CNQX, or TTX to the proximal basilar dendrites did not abolish electrographic seizures but instead selectively suppressed the intracellularly recorded sustained depolarization and the coincident slow negative field potential recorded in proximal basilar dendrites. Results of several experiments suggest that electrographic seizures recorded under these conditions were produced by a remote network of "generator cells." Since the remote neurons were unaffected by local application of the drugs, it seemed likely that they continued to undergo a sustained depolarization. Simultaneous blockade of basilar dendritic synapses in the "generator" population abolished electrographic seizures throughout these larger minislices. These results suggest that the sustained depolarization plays a central role in seizure generation and that it does not have to be generated in every neuron, only in a critical number of "generator cells" for a seizure to occur. Taken together, results presented here suggest that the sustained depolarization of electrographic seizures is a separate physiological process from the more rapid repetitive depolarizations of the seizure discharges and is required if electrographic seizures are to occur. This slow depolarization appears to be synaptically mediated and generated exclusively in proximal basilar dendrites. Therefore, in addition to the excitatory synaptic potentials involved in paroxysmal depolarization shift generation, a second form of recurrent excitation may exist in immature hippocampus. Not only is this physiological process critical for the genesis of seizures, but it also appears to be highly partitioned within the hippocampal laminae.

Interspecific conjugal transfer of antibiotic resistance among staphylococci isolated from the bovine mammary gland

In vitro transferability of penicillin, streptomycin, tetracycline, and erythromycin resistance from coagulase-negative staphylococci to Staphylococcus aureus and among the former species of bovine mammary gland origin was examined by bacterial mating on filters and by mixed-culture matings in broth and in skim milk. One hundred twenty-six (42 each on filter, in broth, and in skim milk) matings were performed among 37 isolates of different Staphylococcus species. Transfer of resistance to penicillin, tetracycline, or erythromycin was not detected. Of 51 matings performed to determine streptomycin-resistance transfer, 9 (3 each on filters, in broth, and skim milk) were successful. Nine strains representing 3 species of coagulase-negative staphylococci were tested as prospective donors of streptomycin resistance. Of these, 2 strains could transfer streptomycin resistance. A double-resistant donor, S hominis, not only transferred its streptomycin resistance to an S chromogenes strain lacking resistance, but also to an S aureus strain already carrying penicillin and tetracycline resistance. The transfer of streptomycin resistance from the donor S hominis, harboring 2 plasmids, to a plasmidless S chromogenes recipient strain was associated with apparent acquisition of the smaller plasmid of the donor by the recipient. The single-resistant donor, S epidermidis 681A, transferred streptomycin resistance to a tetracycline-resistant S aureus recipient. This strain however, failed to transfer its streptomycin resistance to another S aureus, 2 S hyicus, and 1 S xylosus recipient. Frequency of transfer of streptomycin resistance ranged from 1.1 x 10(-5) to 1 x 10(-4). When transfer of resistance was successful, attempts were made to characterize the transfer process.(ABSTRACT TRUNCATED AT 250 WORDS)

Botulinum B toxin as an alternative to botulinum A toxin: a histologic study

Histochemical effects of botulinum B toxin were studied on fibers from longissimus dorsi muscle in Albino rabbits and compared to effects produced by botulinum A toxin. Acetylcholinesterase staining, muscle fiber size analysis, and ATPase staining indicated botulinum B toxin produced a denervation gradient and field similar to that produced by botulinum A toxin. At 5 weeks postinjection with botulinum B toxin, analysis showed muscle fiber size variability, and diffuse acetylcholinesterase fiber staining comparable to botulinum A toxin at the injection site. Muscle sections taken at 4.0 cm for analysis showed statistically significant decreased fiber size variability and contraction of acetylcholinesterase staining pattern for both immunotypes. In addition, the denervation reflected by histochemical staining and fiber size analysis appeared transient and lasted for approximately 3 months for both immunotypes. These findings suggest botulinum B toxin produces pharmacologic effects on innervation of striated muscle similar to botulinum A toxin. Because immunologic tolerance has been demonstrated after therapeutic botulinum A toxin injections, further clinical studies need to be conducted with other immunotypes of toxin with no cross-reactivity to type A.

Role of vitamin E and selenium in host defense against mastitis

Vitamin E and Se are essential nutrients that share common biological activities. Deficiencies in either of these micronutrients have been related in increased incidence and severity of mastitis. A known physiological consequence of alpha-tocopherol or Se deficiency is reduced neutrophil activity. Vitamin E and the Se-containing enzyme, glutathione peroxidase, and antioxidants that protect neutrophils from the destructive action of toxic oxygen molecules necessary for intracellular kill of ingested pathogens. Dietary supplementation of cattle with Se results in a more rapid neutrophil influx into milk following intramammary bacterial challenge and increased intracellular kill of ingested bacteria by neutrophils. Dietary supplementation of early lactation cows with vitamin E results in increased bactericidal activity by bovine blood neutrophils. Recently completed trials have shown that subcutaneous injections of vitamin E approximately 10 and 5 d prior to calving successfully elevated neutrophil alpha-tocopherol concentrations during the periparturient period and negated the suppressed intracellular kill of bacteria by neutrophils that is commonly observed at calving.

Mechanism of muscle protein degradation in cancer cachexia

Depletion of skeletal muscle mass in animals bearing an experimental model of cachexia, the MAC16 adenocarcinoma, occurs by a reduction in protein synthesis accompanied by a large increase in protein degradation. Serum from mice bearing the MAC16 tumour produced an increased protein degradation in isolated gastrocnemius muscle, as measured by tyrosine release, with a maximal effect occurring with serum from animals with a weight loss of between 11 and 20%. The response was specific to the cachectic state, since serum from mice bearing the MAC13 adenocarcinoma, which does not produce weight loss, did not increase tyrosine release from gastrocnemius muscle above that observed with serum from non tumour-bearing animals. The circulatory proteolysis-inducing factor was stable to heating at 60 degrees C for 5 min and was not inhibited by phenylmethylsulfonyl fluoride, suggesting that it was not a serine protease. The level of prostaglandin E2 (PGE2) in gastrocnemius muscle was significantly elevated after incubation with serum from cachectic mice bearing the MAC16 tumour. Both indomethacin and the polyunsaturated fatty acid eicosapentaenoic acid (EPA) inhibited the rise in muscle PGE2 content in response to serum from cachectic mice and also inhibited muscle protein degradation. These results suggest that muscle protein degradation in cancer cachexia is associated with a rise in PGE2 content.

PCR detection of cytomegalovirus: a review

CMV is of major concern in immunocompromised and immunosuppressed patients. Since CMV can be transmitted by leucocyte transfusions from healthy seropositive donors (Hirsch, 1984) it has been stated that leucocytes are the natural reservoir of latent CMV (Jiwa et al, 1989). Although tissue culture is the method currently used for the diagnosis of CMV infection, this technique is time consuming, expensive and does not detect latent virus. As 80% of normal Australian blood donors are seropositive for CMV (Ho, 1990) the amount of blood available for high risk patients is greatly reduced. The dramatic gains in sensitivity of viral detection made possible by the PCR technique offers new hope for the detection of otherwise elusive latent genomes as well as more routine application in the detection of viraemia or other active infection. However, for this technique to be adopted by clinical laboratories it must be shown to be easily reproducible and cost-effective. Thus, the PCR may have an important role in the development of CMV-negative blood products, as well as being a powerful test in diagnostic virology. It is expected that it will reduce the morbidity and mortality rate in susceptible patients at risk of CMV when given transfusions of blood from subjects who may carry the virus.

Detection of cytomegalovirus in blood donors by the polymerase chain reaction

A polymerase chain reaction (PCR) assay was developed and optimized to detect cytomegalovirus (CMV) DNA in the blood of 86 normal donors who had originally tested seropositive for CMV. Evidence of previous or current infection with CMV was determined by rescreening of the blood for CMV antibodies and by detecting the presence of infectious virus in the white cells by cell culture. DNA was extracted from the blood of donors by a manual or an automated method and amplified by PCR using primers from the major immediate early gene of CMV DNA. The amplified product was detected by visualization of a fluorescent 435-base pair DNA band in an electrophoretic agarose gel after ethidium bromide staining and confirmed by slot-blot DNA hybridization using an oligonucleotide probe with complementarity for the major immediate early gene. Seven (8%) of the 86 donors were positive for CMV DNA in both fluorescence and hybridization studies. These donors were also antibody positive. While 74 (86%) of the 86 donors were positive for the presence of CMV antibodies in enzyme-linked immunosorbent assay, none was positive for virus in cell culture. PCR has the potential to be an effective and reliable procedure for the detection of CMV DNA in donor blood, but further study is required for this technique to be used for diagnostic or routine screening purposes.

Association of abnormal uterine discharge with new intramammary infection in the early postpartum period in multiparous dairy cows

The association of abnormal uterine discharge with the development of intramammary infection (IMI) was studied in 62 multiparous Holstein cows during the nonlactating period and from lactation days 3 through 30. Duplicate milk samples were obtained from each mammary gland at approximately day 30 of the nonlactating period. Milk samples for bacteriologic culture also were obtained from each gland from all cows at the end of the previous lactation, at parturition, and on a minimum of 7 additional dates during the first 30 days of lactation. Beginning after parturition and continuing once weekly for 4 weeks, each cow was examined, using a vaginal speculum to visually estimate the quantity of abnormal uterine discharge in the vagina. Additionally, uterine swab specimens were obtained for aerobic bacteriologic culture. Cows were allotted to groups on the basis of the maximal amount of abnormal uterine discharge observed at any 1 of the 4 examinations. Cows in group 1 had normal discharge or < 30 ml of abnormal discharge; in group 2, > or = to 30 ml of abnormal discharge, observed only on examination by vaginal speculum; and in group 3, > or = to 30 ml of abnormal discharge visible externally. A difference was not detected in the development of new IMI in the nonlactating period between cows that subsequently developed uterine discharge and those that did not. Although significant differences were not found, a tendency for lactating cows with abnormal uterine discharge to be at increased risk for developing new IMI was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased protein degradation and decreased protein synthesis in skeletal muscle during cancer cachexia

The effects of progressive cachexia on protein metabolism in skeletal muscle has been investigated in mice bearing the MAC16 adenocarcinoma which produces cachexia with tumour burdens of < 1% of the host weight. Weight loss was accompanied by loss of whole body nitrogen in proportion to the overall loss of body mass. Using L-[4-3H]phenylalanine to label proteins in gastrocnemius muscle, a significant depression (60%) in protein synthesis occurred in animals with a weight loss between 15 and 30% accompanied by an increase in protein degradation, which increased with increasing weight loss between 15 and 30%. Muscle degradation in vitro could be achieved by serum from cachectic animals, which appeared to contain a proteolysis-inducing factor. These results suggest that the increased degradation of skeletal muscle seen in this model of cachexia may be due to a circulating proteolysis-inducing factor.

Growth responses of coliform bacteria to recombinant bovine cytokines

Growth responses of 10 coliform isolates to recombinant bovine cytokines were measured in vitro. Six Escherichia coli and four Klebsiella pneumoniae isolates obtained from bovine IMI were tested for growth responses to recombinant bovine interleukin-1 beta, interleukin-2, and interferon-gamma. Cytokines were tested at 10(4), 10(3), 10(2), and 10 U/ml of media. Media used were a synthetic tissue culture medium, a chemically defined synthetic bacterial growth medium, and UHT sterilized milk. Bacterial counts in the synthetic tissue culture medium and UHT milk increased slightly as concentration of interferon-gamma in the media increased. Recombinant bovine interferon-gamma increased bacterial populations during the log growth phase but did not affect the number of bacteria in stationary growth phase. Bacterial growth responses were not related to either interleukin-2 or interleukin-1 beta concentrations in any of the three media. Bacterial growth responses to cytokines were not related to differences in either serum susceptibility, growth of isolates in dry cow secretion, duration of IMI from which isolates were obtained, or bacterial species.

Removal of cytomegalovirus DNA from donor blood by filtration

Blood from five donors, previously shown to be positive for cytomegalovirus (CMV) DNA following polymerase chain reaction (PCR) amplification, was filtered through commercially available leucocyte filters. Analysis of pre- and post-filtration samples by PCR with ethidium bromide staining has shown that filtration was successful in removing CMV DNA from all samples. This is evidence that leucocyte filtration of red cell concentrates may greatly decrease the risk of CMV disease following transfusion to susceptible patients.

Late functional outcome in patients with tibia fractures covered with free muscle flaps

The functional outcome and work capacity of patients treated with a free muscle flap to cover open grade III tibial fractures was assessed. The conditions of patients, eight with grade IIIB and six with grade IIIC isolated open tibia fractures, treated with a free muscle flap transfer less than 3 months after their injury, were retrospectively reviewed. Flap survival was 86%. Twelve of the 14 were contacted, with follow-up time averaging 7 years. Four of the 14 eventually had below-knee amputations and one of the 10 patients with a successful limb salvage died of unrelated causes. All nine surviving patients with salvaged limbs had healed fractures in an average of 15 months (range, 8-23). Six were initially infected, but drainage had stopped an average of 13.5 months after flap coverage. No wounds were draining at last follow-up observation. Those tibias that were initially infected have been drainage free for an average of 78 months. The average total hospital cost of reconstruction was $48,996.40. The functional outcome in 12 patients was assessed. Eight of the nine patients whose limbs were salvaged returned to work, six to jobs with demands similar to their preinjury occupation. Three of the four patients with limb amputations were also able to return to jobs similar to their preinjury occupation. Patients must be made aware of the expected course of reconstruction and anticipated final outcome. Despite rarely achieving normal function, returning to work is a reasonable goal.

Characteristics of coagulase-negative Staphylococci isolated from bovine intramammary infections

Coagulase-negative Staphylococci (CNS) isolated from 86 different bovine intramammary infections (IMI) were investigated for their plasmid content, antimicrobial resistance, and infection characteristics. Plasmids were isolated from 30.2% of CNS. Number of plasmid bands ranged from 1 to 5. With the exception of tetracycline resistance, the presence of plasmids was not related to antibiotic resistance. Staphylococcus chromogenes was the CNS most frequently isolated from bovine IMI. Intramammary infections were of long duration (mean = 222 days) and resulted in a low incidence of clinical mastitis (8.1% of IMI). The greatest percentage of IMI (55%) were detected in heifers with 57% of these IMI first detected at calving. A total of 56% of IMI originated during the dry period in second lactation or older cows. The number of plasmid-positive CNS IMI was greater (P < 0.05) in multilactational cows when compared to heifers. The presence of a plasmid-positive CNS had no influence on duration of IMI, origin of IMI, clinical status of the infection, and elimination of IMI.

Lexical-phonological processing of functors: evidence from fluent aphasia

The purpose of this study was to investigate how functors are processed at the lexical-phonological level. Four fluent aphasics with impaired ability to fully activate entries in the phonological lexicon, as revealed by their noun production, were asked to repeat and read aloud individual functors. Similarities between their functor and noun production (e.g., level of performance, production of phonological errors) indicated that functors are stored along with content words in the phonological lexicon, and are stored with a similar abstract structure. We also considered whether the sentence-planning system can facilitate the phonological encoding of functors presented in isolation.

Renin and renin inhibition in anephric man

Renin activity appears to be present in low concentrations in the plasma of anephric humans but could be artifactual secondary to inadvertent activation of prorenin during specimen collection and handling or from a renin-like enzyme. We studied the effects of specimen collection, storage, different assay conditions, trypsin activation, and the renin inhibitor EMD 56133 (E Merck, Darmstadt) on plasma renin activity (PRA) in anephric man. PRA was detectable in all seven bilaterally nephrectomized (BNX) patients (0.2 +/- 0.1 ng AI/ml/hr, range 0.1-0.7) but was significantly lower than normals (2.4 +/- 0.3 ng AI/ml/hr, range 1.5-3.1, p = 0.001). PRA was not different in BNX whether blood samples were collected on ice or at room temperature and assayed immediately or whether samples were frozen and assayed several days later. Prolonged cold storage of samples and five freeze-thaw cycles over six to seven months did not significantly increase PRA in normals or anephrics. However, deliberate repeated freezing and thawing over the period of a single day increased PRA 4.1-fold in BNX and 1.6-fold in normals. Renin-like activity was also detected in BNX individuals using renin concentration determinations with either excess human or sheep angiotensinogen. The inhibition of renin activity (IC-50% = 3.16 x 10(-9) molar) by EMD 56133 was not different between BNX and normals. Thus, active renin is present in the plasma of anephric humans and does not result from the inadvertent activation of prorenin due to sample handling. Although the source of PRA in BNX is unknown, the enzyme appears functionally normal as evidenced by the dose-response to a single renin inhibitor.

Vitamin E as an adjuvant in an Escherichia coli J5 vaccine

Vitamin E was tested as an adjuvant in an Escherichia coli (O111:B4) J5 vaccine. Twenty cows were assigned to five groups of 4 cows. Cows in four groups were vaccinated with an E. coli J5 bacterin containing 5 ml of 10(9) boiled cells/ml. Vaccinations were at drying off, 30 d after drying off, and within 48 h after calving. Vaccine adjuvants differed among groups. The four treatment adjuvants were 5 ml of Freund's incomplete adjuvant, 5 ml of vitamin E, 2.5 ml of Freund's plus 2.5 ml of vitamin E, and 5 ml of PBS. Cows in the fifth group were unimmunized controls. A front mammary quarter of each cow was challenged by infusion of 10 micrograms of E. coli J5 lipopolysaccharide approximately 4 wk into lactation. Vitamin E alone enhanced serum IgM titers but had no effect on milk IgM or serum and milk IgG titers. The mixture of Freund's plus vitamin E resulted in peak IgG titers in serum and milk comparable with that of Freund's alone. Persistency of IgG titers in cows immunized with the Freund's plus vitamin E mixture was greater than the persistency of titers for cows immunized with the vaccine containing Freund's alone as the adjuvant. The mixture of Freund's plus vitamin E had a synergistic effect in reducing severity of systemic clinical signs.

Observations on the inhibition of serum and cell surface enzymes by eicosapentaenoic acid

The relationship between serum and tumour cell surface proteolytic enzymes and the development of muscle breakdown in cancer cachexia has been studied in a murine model of the condition (MAC16). The surface of the MAC16 tumour cells carried a proteolytic enzyme referred to as guanidinobenzoatase (GB). Serum from mice also contained an enzyme (referred to as MSE) which cleaved the trypsin inhibitor 4-methylumbelliferyl-p-guanidinobenzoate as a true substrate, but there was no relationship with weight loss or the presence or absence of tumour and the level of this serum enzyme. Polyunsaturated fatty acids (PUFAs) were shown to be inhibitors of MSE at microM concentrations and one PUFA, eicosapentaenoic acid (EPA) was found to be a non-competitive inhibitor of both MSE and GB. The effect of EPA was specific since other proteolytic enzymes, trypsin, esterase and tissue plasminogen activator were unaffected by concentrations inhibiting GB and MSE. MSE and GB are two different enzymes which possess some common properties. However, GB is likely to be significant for tumour development since MSE is also found in normal mouse serum.

Susceptibility of Escherichia coli isolated from intramammary infections to phagocytosis by bovine neutrophils

Thirteen Escherichia coli isolated from naturally occurring IMI were tested for susceptibility to phagocytosis by bovine blood neutrophils. Isolates were opsonized in pooled serum collected from nine healthy lactating cows. Bacteria isolated from IMI first diagnosed within 3 d after calving were more resistant to phagocytosis than were isolates from IMI originating during either the first half of the dry period or later during lactation. Duration of the IMI was negatively correlated with both phagocytic index and percentage of neutrophils phagocytizing within bacterial isolates from IMI originating at calving and during lactation. Phagocytosis was independent of duration of IMI within isolates from IMI originating during the first half of the dry period. Susceptibility to in vitro phagocytosis by neutrophils was not related to O antigen serotype, encapsulation, or growth in dry cow secretion.

Effect of supplementing periparturient cows with vitamin E on distribution of alpha-tocopherol in blood

Holstein cows were fed 0 or 1000 IU/d of supplemental vitamin E during the dry period and injected with placebo or 3000 IU of vitamin E at 10 and 5 d prior to anticipated calving. Blood was collected at various times, starting at 60 d prepartum (dry off) and concluding 30 d postpartum, and separated into plasma, red blood cells, and neutrophils. Oral supplementation increased concentrations of alpha-tocopherol in plasma and red blood cells on 10 d, but not on 5 d prepartum. Injection of vitamin E increased alpha-tocopherol in plasma, red blood cells, and neutrophils at d 5 prior to and on the day of parturition. Concentrations of alpha-tocopherol and cholesterol in plasma were correlated, and both were at their nadir at parturition. Concentrations of alpha-tocopherol in plasma and red blood cells were correlated, but the correlation increased when plasma alpha-tocopherol was expressed per unit of cholesterol. alpha-Tocopherol in plasma and neutrophils had a low correlation. Injection of alpha-tocopherol increased its concentration in plasma, red blood cells, and neutrophils during the periparturient period. Concentration of alpha-tocopherol in plasma of periparturient cows may be limited by its low lipid content, and transport mechanisms for alpha-tocopherol may differ between red blood cells and neutrophils.

Displacement of an uncemented acetabular component after dislocation of a total hip prosthesis. A case report

Review of the literature reveals few reports of complications encountered with noncemented acetabular components; most concern problems with screw or cup placement, component wear or migration, or disassembly of modular components. No reports involving the displacement of a noncemented acetabular component were found. This is a case report of a patient in whom a noncemented acetabular component was dislodged after the closed reduction of a dislocated total hip prosthesis 4.5 weeks after surgery. In light of this case, the authors believe these reductions should be performed under general anesthesia with fluoroscopic guidance. Care must be taken at surgery to ream sufficiently and obtain proper cup fit and position. Finally, the authors recommend bicortical screw fixation to provide maximum contact and rigid fixation in the early postoperative period.

Determination of conditions for optimum resolution of a high angle thin window energy dispersive spectrometer

The energy resolution of an energy dispersive spectrometer (EDS) equipped with an ultrathin window (UTW) and mounted at a high take-off angle (72 degrees) on a transmission electron microscope has been studied under a variety of operating conditions. The spectrometer resolution is close to that specified by the manufacturer, up to count rates of 400 cps. Above 400 cps the resolution deteriorates rapidly, and the MCA dead time and zero width increase. Above 10 keV, the height of the background is much greater than expected for bremsstrahlung and shows the shape which has previously been attributed to backscattered electron flux into the detector. It is postulated that the deterioration in resolution with count rate is caused by backscattered electrons reaching the detector through the UTW.

Prevention of human rotavirus-induced diarrhea in gnotobiotic piglets using bovine antibody

The efficacy of passively administered bovine antibody for preventing human rotavirus (HRV)-induced diarrhea was investigated using a gnotobiotic pig model. Cows were immunized with inactivated HRV serotypes 1 (Wa) and 2 (S2) and simian rotavirus serotype 3 (SA11), and immune colostrum and milk were collected. Antibody concentrates derived from these materials were fed to germ-free piglets that were subsequently inoculated with HRV Wa. Both viral shedding and diarrhea were effectively reduced or eliminated in a dose-dependent manner as a result of HRV immune antibody feeding. A quantitative virus-neutralizing (VN) antibody method permitted assessment of the functional antibody dose required to achieve a 50% reduction of disease (PD50). PD50 dose levels of 15.8 and 19.5 x 10(6) VN antibody units were determined for inhibition of diarrhea and viral shedding, respectively. Studies reported here provide new information on the quantitative relationship between protective antibody dose and diarrheal disease response.

Lateral band translocation for swan-neck deformity

Lateral band translocation involves transfer of the dorsally subluxed radial lateral band to the palmar aspect of the joint where it is maintained by a sling created between the flexor superficialis tendon and the palmar plate. Thirty fingers with swan-neck deformity of differing causes and a preoperative hyperextension deformity averaging 16 degrees were treated. After operation all swan-neck deformities were corrected and the average flexion contracture was 11 degrees. The range of preoperative flexion was either regained or improved. There were no recurrences and no complications. This relatively simple procedure is an effective treatment of swan-neck deformity and an attractive alternative to previously described procedures.

Bovine neutrophil responses to parenteral vitamin E

Twenty-eight Holsteins were tested to determine effects of dietary and parenteral vitamin E supplementation during the dry period on plasma alpha-tocopherol and in vitro neutrophil functions at calving. Cows were assigned to one of four experimental groups receiving either supplemental dietary vitamin E, injections of vitamin E, both dietary and injections of vitamin E, or neither source of supplemental vitamin E during the dry period in a 2 x 2 factorial arrangement. Cows receiving parenteral vitamin E were injected subcutaneously with 3000 IU of vitamin E (dl-alpha-tocopherol) at 10 and 5 d prior to anticipated calving. Cows not receiving parenteral vitamin E were injected with a placebo. Experimental groups receiving dietary vitamin E during the dry period were supplemented with 1040 IU/d compared with none for controls. Cows injected with vitamin E had greater plasma alpha-tocopherol concentration 5 d after the first injection, at calving, and 1 wk after calving than did cows injected with placebo. Plasma alpha-tocopherol concentrations did not differ between dietary vitamin E treatment groups from calving through 4 wk postpartum. No interaction was found between dietary and parenteral supplementation of vitamin E on plasma alpha-tocopherol concentration. Neutrophils from cows injected with vitamin E had greater intracellular kill of bacteria at calving than did neutrophils from placebo-injected cows. Neither phagocytic index nor percentage of neutrophils phagocytizing differed between vitamin E-injected and placebo-injected cows. Dietary vitamin E during the dry period had no effect on neutrophil function at calving. Intracellular kill and plasma alpha-tocopherol were correlated at calving.

Accurate measurement of the dihedral angle of a corner cube

The alignment of a corner cube affects the measurement of its dihedral angle. For 5 deg of tilt, the error is up to 7%, depending on the orientation of the tilt. A vector model is devised to derive formulas that take misalignment into account for both solid and hollow corner cubes. When the wave-front tilt caused by the dihedral angle error is not much greater than that caused by the surface figure, because of vignetting for a tilting illumination, the surface figure of the cube facet makes varying contributions to the wave-front tilt for different incident angles. Simulations and experimental results are presented.

Efficacy of an Escherichia coli J5 mastitis vaccine in an experimental challenge trial

An Escherichia coli (O111:B4) J5 bacterin was tested for efficacy in reducing IMI and severity of clinical coliform mastitis in an experimental challenge trial. Ten cows were immunized at drying off, 30 d after drying off, and at calving. Ten control cows were not immunized. Right front quarters of all cows were infused with a heterologous strain of E. coli approximately 30 d after calving. Vaccinated cows had lower bacterial counts in milk and lower rectal temperatures than unvaccinated controls following intramammary challenge. Milk production and DMI were more depressed in controls than in vaccinated cows. Milk SCC did not differ between experimental groups. Mean serum IgG titer to whole cell E. coli J5 was significantly greater in vaccinated than in unvaccinated cows at 30 d after drying off, day of challenge, and 7 d postchallenge. Milk IgG titer to E. coli J5 was higher at challenge in vaccinated than in control cows. Vaccination with the E. coli J5 bacterin did not prevent IMI but did reduce severity of clinical signs following intramammary experimental challenge with a heterologous E. coli strain.

Opsonic activity of bovine serum and mammary secretion after Escherichia coli J5 vaccination

Six pairs of cows were used to determine the effects of immunization with an Escherichia coli (O111:B4) J5 bacterin on in vitro opsonization of a smooth heterologous strain of E. coli. One cow in each pair was either immunized with the vaccine or sham-immunized at drying off, 30 d after drying off, and at calving. Opsonizing bacteria with serum collected from vaccinated cows 21 d after calving resulted in higher mean number of intracellular bacteria per phagocytosing neutrophil than opsonizing bacteria with serum collected from control cows. Phagocytic parameters using serum collected at drying off and calving did not differ between treatment groups. A trend for enhanced opsonic activity of colostrum from vaccinates was noted. Enhanced opsonization by serum from vaccinated cows coincided with higher serum IgM titer to E. coli J5 whole cell antigen compared with controls. Serum IgG titers to E. coli J5 did not differ between groups. Colostrum IgG titers to E. coli J5 were greater at calving in vaccinated than in control cows. Colostrum and milk collected 21 d after calving from vaccinated cows had higher IgM titers to E. coli J5 than did mammary secretions from control cows. Numbers of intracellular bacteria per phagocytizing neutrophil were correlated positively with IgM titers to E. coli J5 in both serum and colostrum.

Field trial to determine efficacy of an Escherichia coli J5 mastitis vaccine

Efficacy of an Escherichia coli (O111:B4) J5 bacterin for preventing naturally occurring IMI and clinical mastitis was tested in a 2.5-yr field trial in a 225-cow commercial herd. Cows with odd-numbered identification were vaccinated, and cows with even-numbered identification served as unvaccinated controls for each lactation during the study. Immunizations were subcutaneous on the upper part of the rib cage just posterior to the scapula at drying off, 30 d after drying off, and at calving. Percentage of quarters infected at calving with Gram-negative bacteria did not differ between treatment groups. A total of 67% of Gram-negative bacterial IMI present at calving in control cows became clinical during the first 90 d of lactation compared with 20% in vaccinated cows. Rate of Gram-negative bacterial clinical mastitis was higher in control cows than in vaccinated cows during the first 90 d of lactation. Immunization with the E. coli J5 bacterin did not reduce level of Gram-negative bacterial IMI at calving but did reduce incidence of clinical mastitis.

The relationship between oral spelling and phonological breakdown in a conduction aphasic

Unsolicited oral spelling has been observed in conduction aphasics during word-production difficulty (Kohn, 1985), but has never been examined systematically. In the present study, the possible role of oral spelling in the word-production process of a conduction aphasic (JM) is explored. Oral spelling occurred much more frequently during picture naming than during either oral reading or repetition, and it seemed to be operating as a strategy to lessen the phonemic output deficit often observed in this syndrome.

Anticachectic and antitumor effect of eicosapentaenoic acid and its effect on protein turnover

The effect of the polyunsaturated fatty acids eicosapentaenoic acid (EPA) and gamma-linolenic acid (GLA) on host body weight loss and tumor growth has been investigated in mice bearing a cachexia-inducing colon adenocarcinoma, the MAC16. EPA effectively inhibited both host weight loss and tumor growth rate in a dose-related manner with optimal effects being observed at a dose level of 1.25 to 2.5 g/kg. At these concentrations host body weight was effectively maintained, and there was a delay in the progression of growth of the tumor, such that overall survival was approximately doubled in EPA-treated animals, using the criteria dictated by the United Kingdom Coordinating Committee for the welfare of animals with neoplasms. Even when tumor growth resumed, weight loss did not occur. Animals bearing the MAC16 tumor showed a decreased protein synthesis and an increased degradation in skeletal muscle. Treatment with EPA significantly reduced protein degradation without an effect on protein synthesis. The effect of GLA on both host body weight loss and tumor growth was much less pronounced than that of EPA, with an effect only being seen at a dose of 5 g/kg, at which some toxicity was observed. In vitro studies showed that while EPA was effective in inhibiting tumor-induced lipolysis, GLA was ineffective in this respect. However, prostaglandin E1, which is formed from GLA in vivo, showed partial reversal of tumor-induced lipolysis and probably accounted for the anticachectic effect of GLA. These results suggest that EPA as the pure fatty acid should be considered for clinical investigation as both an anticachectic and antitumor agent, since prior work has shown that the other major component of fish oil docosahexaenoic acid is without pharmacological activity in this system.

Comparison of probiotic and antibiotic intramammary therapy of cattle with elevated somatic cell counts

The effects of treating subclinical mastitis with intramammary infusions of either a Lactobacillus or an antibiotic preparation on intramammary infection cure rate and on milk SCC were compared. Cows with two consecutive monthly DHIA composite SCC greater than 300,000 cells/ml (5.4771 log10/ml) were defined as high SCC cows. Twenty-six subclinical cows were randomly assigned to one of two treatments. Quarter foremilk samples were obtained from all quarters at d 0, 7, and 14 following infusion to determine the microbiological status and SCC. Composite milk SCC were determined monthly by DHIA and at d 0, 7, and 14 of the study. Coagulase-negative staphylococci were the predominantly isolated pathogens. Treatment of cows with Lactobacillus cured 21.7% of infected quarters, whereas 73.7% of infections treated with antibiotic were eliminated. Treatment of quarters with antibiotic did not reduce quarter SCC unless infected quarters were cured. Intramammary infusion of quarters with Lactobacillus increased quarter SCC, mainly because of an increase in SCC of initially uninfected, low SCC quarters. Monthly composite SCC were similar between treatments. The results indicate that administering Lactobacillus or antibiotic treatment to all quarters based on elevated composite SCC should not be adopted. Lactobacillus treatment increased SCC with no effect on infection rate.

Age-dependent alterations in the operations of hippocampal neural networks

Results from numerous studies suggest that the functioning of rat hippocampal neural networks during the second postnatal week of life differs distinctly from that in the mature brain. During this critical period, network behavior might be considered hyperexcitable. Spontaneous network-driven bursts of synaptic potentials, which have not been reported in mature hippocampus, are commonly observed. While these events could be attributable to a late onset of GABAergic synaptic transmission, results suggest that this is not the case. In the immature hippocampus orthodromic stimulation leads to prolonged depolarizations and often repetitive synchronized discharging of the entire CA3 population. These events are in many ways reproduced by application of drugs that suppress GABAergic synaptic transmission. The synchronized discharging of the CA3 population is blocked by excitatory amino acid antagonists. This finding, coupled with our growing understanding of the role that recurrent excitation plays in CA3 network functioning, has led to the hypothesis that the differences in network behavior early in life may be largely attributable to an overabundance of local-circuit recurrent excitatory synapses. With maturation, axon collaterals and attendant synapses would regress to achieve an adult complement. Results from dual intracellular recordings as well as anatomical studies of individual CA3 pyramidal cells support this hypothesis. Unique properties of the NMDA receptor at these recurrent excitatory synapses early in life may also promote network excitability. The participation of extracellular Ca2+ in the voltage dependency of the NMDA receptor-linked iontophore could also contribute to synapse consolidation during maturation and thus in the establishment of network connectivity.