Following the forsaken: a procedural description of a problem-based learning program in a school of nursing studies

This paper reports the findings of one stage in an ongoing project to evaluate, from the students' perspectives, a student-centered problem-based learning (PBL) program in a School of Nursing Studies. We begin by making a comparison between teacher-centered education and religious devotion, and liken PBL to a congregation without a priest. A topographical account of the setting follows, describing the typical activities and events that characterize the program. Throughout the course of this account, a number of issues arise: the role of the facilitator, group dynamics, mutual responsibility and motivation for learning. These are touched on briefly, but we do not attempt to make a substantive theoretical contribution. Despite the widespread popularity of PBL in nursing schools, there have been few empirical studies conducted and, consequently, the adoption of PBL in nursing has been dependent upon the research of the very different discipline of medicine and medical education.

Long-term discrepancy between food supply and demand in the deep eastern north pacific

A 7-year study of food supply [sinking particulate organic carbon (POC)] and food demand [sediment community oxygen consumption (SCOC)] in the abyssal eastern North Pacific revealed a long-term deficit in food supply. The POC:SCOC ratio decreased by 52 to 59 percent between 1989 and 1996. A possible explanation for this trend is the documented sea surface temperature increase and concomitant plankton biomass decrease in the eastern North Pacific, resulting in an apparent reduction in POC export from surface waters to the deep ocean. Continuation of this trend could profoundly impact geochemical cycling as well as the structure and dynamics of deep-sea communities.

Efficacy of an Escherichia coli J5 bacterin administered to primigravid heifers

The efficacy of an Escherichia coli J5 bacterin for reducing the incidence of intramammary infections and clinical signs of mastitis was tested in first lactation heifers. Ten primigravid heifers were immunized with an E. coli J5 bacterin. Four heifers received a placebo. The bacterin and placebo were injected subcutaneously approximately 60 d prior to calving, 28 d later, and within 48 h after calving. Vaccinated and placebo-injected heifers were challenged by intramammary infusion of E. coli 727 in one mammary gland between 23 and 37 d after calving. All challenged quarters were diagnosed with an intramammary infection within 6 h after bacteria were infused. The severity and duration of local signs of clinical mastitis were reduced in vaccinated heifers compared with placebo-injected heifers. Systemic signs of clinical mastitis were limited and did not differ between treatment groups. Bacteria counts in milk from challenged quarters were lower in vaccinated heifers than in control heifers at 12, 15, and 48 h after challenge. Serum immunoglobulin G titers against whole-cell E. coli J5 antigen at calving were higher in vaccinated heifers than they were in controls. Vaccinated heifers had higher immunoglobulin G titers than did controls in mammary secretions at calving and immediately prior to challenge. Immunization of primigravid heifers with an E. coli J5 bacterin during the last trimester of gestation and at calving reduced the severity and duration of clinical signs following intramammary challenge with a heterologous strain of E. coli.

Posteroinferior glenoplasty can change glenoid shape and increase the mechanical stability of the shoulder

The treatment of recurrent posterior glenohumeral instability remains an unsolved clinical problem. Although various types of capsulorraphy have been advocated, outcome studies indicate that it is difficult to achieve a balance between stability and mobility. Alterations of the bony glenoid for posterior instability have been proposed, but are not well understood from a mechanical perspective. This investigation had 2 purposes: (1) to determine in a cadaver model if posteroinferior glenoplasty can change the shape of the glenoid, and (2) to determine if altering the shape of the glenoid can increase the mechanical stability of the glenohumeral joint. We determined the effective glenoid shape in 7 normal cadaver glenoids by tracking the path of the center of the humeral head as it was translated across the glenoid face in 8 different directions. These determinations enabled us to calculate the maximum effective slope of the glenoid in each direction. We then determined the mechanical stability of the glenoids in each of the 8 directions by measuring the tangential force required to dislocate the shoulder under a 50-N compressive load. The ratio of the dislocating force to the compressive load was defined as the stability ratio. All measurements were repeated after a standardized posteroinferior glenoplasty was performed. Posteroinferior glenoplasty increased the posteroinferior glenoid depth from 3.8 +/- 0.6 mm to 7.0 +/- 1.8 mm and shifted the center of the humeral head an average of 2.2 mm anteriorly and 1.8 mm superiorly. These changes in dimension could be directly visualized as an immediate mechanical consequence of the glenoplasty procedure, particularly because of the insertion of the bone wedge. Glenoplasty increased the posteroinferior glenoid slope from 0.55 +/- 0.07 to 0.83 +/- 0.12 and increased the posteroinferior stability ratio from 0.47 +/- 0.10 to 0.81 +/- 0.17. This is a more than 70% increase in the tangential force that can be resisted before dislocation. The increase can be quantitatively understood as a direct mechanical consequence of the altered shape of the glenoid concavity. These numbers indicate that, in this cadaveric model, posteroinferior glenoplasty results in defined changes in the effective glenoid shape and in the mechanical stability of the glenohumeral joint. However, this study does not establish the role of this procedure in the clinical management of posterior glenohumeral instability.

Long-term depression of perforant path excitatory postsynaptic potentials following synchronous network bursting in area CA3 of immature hippocampus

Various forms of synaptic long-term potentiation and depression have been studied in detail in hippocampus and neocortex. Each are produced by specific patterns of synaptic activation and rely on electrical stimulation of afferents for their induction. Few studies have explored the ability of activity produced by cortical networks themselves to generate similar long-term changes in synaptic efficacy. Experiments have shown that periods of synchronized network bursting in both slices and dissociated cultures of hippocampus can lead to persistent network discharges. Conversely, one study has reported that network discharging can disrupt the induction of long-term potentiation in hippocampus. Whether long-term depression can be induced by synchronous network discharging is unknown. In experiments reported here, we examined the long-term effects of synchronized activity within hippocampal CA3 networks on synaptic potentials produced by the converging perforant path. Prior to induction of network bursting, slices were incubated in a perfusate containing picrotoxin and elevated (4 mM) Ca2+ and Mg2+. To induce network discharges, the concentration of both divalent cations were reduced to normal levels (1.5 mM). Following 20 min of network bursting, perforant path synapses, that did not participate in network discharging, underwent a 30% non-decrementing long-term depression. At the same time, synchronized network discharges, that were absent prior to induction, persisted upon return to preinduction conditions. The antagonist of the N-methyl-D-aspartate receptor, D(-)2-amino-5-phosphonovalerate, blocked both long-term depression of perforant path excitatory postsynaptic potentials and persistent network discharging. Results suggest that activity generated by hippocampal networks is able to produce long-term depression of non-coincidentally active synapses.

Rapid resetting of the mammalian circadian clock

The suprachiasmatic nuclei (SCN) contain the principal circadian clock governing overt daily rhythms of physiology and behavior. The endogenous circadian cycle is entrained to the light/dark via direct glutamatergic retinal afferents to the SCN. To understand the molecular basis of entrainment, it is first necessary to define how rapidly the clock is reset by a light pulse. We used a two-pulse paradigm, in combination with cellular and behavioral analyses of SCN function, to explore the speed of resetting of the circadian oscillator in Syrian hamster and mouse. Analysis of c-fos induction and cAMP response element-binding protein phosphorylation in the retinorecipient SCN demonstrated that the SCN are able to resolve and respond to light pulses presented 1 or 2 hr apart. Analysis of the phase shifts of the circadian wheel-running activity rhythm of hamsters presented with single or double pulses demonstrated that resetting of the oscillator occurred within 2 hr. This was the case for both delaying and advancing phase shifts. Examination of delaying shifts in the mouse showed resetting within 2 hr and in addition showed that resetting is not completed within 1 hr of a light pulse. These results establish the temporal window within which to define the primary molecular mechanisms of circadian resetting in the mammal.

Asymmetric membrane capsules for osmotic drug delivery. I. Development of a manufacturing process

This paper describes a novel non-disintegrating polymeric capsule and a manual and a semi-automatic process developed for its manufacture. The capsule wall was made by a phase inversion process in which the membrane structure was precipitated on stainless steel mold pins by dipping the mold pins into a coating solution containing a polymer-solvent-nonsolvent system followed by dipping into a quench solution. The resulting asymmetric membrane wall was composed of a thin dense region supported on a thicker porous region. The asymmetric membrane capsules can be filled with a blend of the active agent and excipients for use in osmotically modulated controlled drug delivery applications.

Growth responses of coliform bacteria to purified immunoglobulin G from cows immunized with ferric enterobactin receptor FepA

The ability of purified bovine immunoglobulin (Ig) G from cows immunized with ferric enterobactin receptor FepA to inhibit the growth of coliform bacteria derived from bovine intramammary infection was investigated in iron-restricted media. All isolates of Escherichia coli (n = 21) and Klebsiella pneumoniae (n = 21) were tested for growth in a chemically defined medium containing 0.5 mg/ml of apolactoferrin and in a pooled source of dry cow secretion. The addition of 4 mg/ml of purified bovine IgG directed against FepA in the synthetic medium resulted in significant growth inhibition for both E. coli and K. pneumoniae isolates. Growth reduction of E. coli was greater than that of K. pneumoniae. In dry cow secretions, the growth of each E. coli isolate but of less than half of K. pneumoniae isolates (43%) was inhibited by IgG from cows immunized with FepA. Purified bovine IgG from cows immunized with E. coli J5 had a minimal inhibitory effect on the growth of both E. coli and K. pneumoniae isolates in the synthetic medium. In dry cow secretions, IgG from cows immunized with E. coli and K. pneumoniae isolates. Supplementation with 50 microM of ferric chloride to the medium completely reversed the inhibitory effects of the antibodies and lactoferrin. Bovine IgG directed against FepA apparently inhibited the growth of coliform bacteria by interfering with the binding of the ferric enterobactin complex to the cell surface receptor FepA.

Syllabic effects in word processing: evidence from the structural induction paradigm

Spoken words have a rich structural organization in memory, consisting of syllabic and subsyllabic representations. A phoneme monitoring paradigm, in which the target phoneme occurs more frequently in one syllabic position than another (e.g., onset of the 2nd syllable vs. the coda of the 1st syllable: neu-tral vs. nut-meg; C. Pallier, N. Sebastian-Galles, T. Felguera, A. Christophe, & J. Mehler, 1993) was used to explore the formation of syllabic structure during word processing. Experiment 2 investigated how a recognition system that uses syllabic structure processes words with unclear syllable boundaries (e.g., pa-lace or pal-ace?). Two methodological issues were explored: The importance of a baseline condition for measuring effects of induction (Experiment 1) and the form of the representation used in the induction paradigm (Experiment 3). Findings suggest that syllabic structure begins to form early in word processing, and they demonstrate the adequacy of the induction procedure for measuring such processes.

Syllabic effects in word processing: evidence from the structural induction paradigm

Spoken words have a rich structural organization in memory, consisting of syllabic and subsyllabic representations. A phoneme monitoring paradigm, in which the target phoneme occurs more frequently in one syllabic position than another (e.g., onset of the 2nd syllable vs. the coda of the 1st syllable: neu-tral vs. nut-meg; C. Pallier, N. Sebastian-Galles, T. Felguera, A. Christophe, & J. Mehler, 1993) was used to explore the formation of syllabic structure during word processing. Experiment 2 investigated how a recognition system that uses syllabic structure processes words with unclear syllable boundaries (e.g., pa-lace or pal-ace?). Two methodological issues were explored: The importance of a baseline condition for measuring effects of induction (Experiment 1) and the form of the representation used in the induction paradigm (Experiment 3). Findings suggest that syllabic structure begins to form early in word processing, and they demonstrate the adequacy of the induction procedure for measuring such processes.

Spine loss and other persistent alterations of hippocampal pyramidal cell dendrites in a model of early-onset epilepsy

To explore the anatomical substrates for network hyperexcitability in adult rats that become chronically epileptic after recurrent seizures in infancy, the dendritic and axonal arbors of biocytin-filled hippocampal pyramidal cells were reconstructed. On postnatal day 10, tetanus toxin was unilaterally injected into the hippocampus and produced brief but recurrent seizures for 1 week. Later, hippocampal slices taken from these rats exhibited synchronized network bursts in area CA3C. Both the apical and basilar dendritic arbors of CA3C pyramidal cells were markedly abnormal in these epileptic rats. There was a considerable reduction in the density of dendrite spines, although the extent of this loss could vary among dendritic segments. Spine density on terminal segments of the basilar and apical dendrites was reduced on average by 35 and 20%, respectively. In addition, the diameters of these same dendritic segments were markedly reduced. Dendritic spine loss has previously been suggested to indicate a partial deafferentation of epileptic neurons, but this interpretation is difficult to reconcile with the critical role recurrent excitatory synaptic transmission plays in the generation of synchronized network burst. In this study, axonal arbors of CA3C pyramidal cells exhibited normal branching patterns, branching complexity, and varicosity density. This suggests that if deafferentation occurs, synapses other than recurrent excitatory ones are lost. The morphological abnormalities reported here would be expected to significantly alter electrical signaling within dendrites that may contribute importantly to seizures and other behavioral sequelae of early-onset epilepsy.

The correlation of comorbidity with function of the shoulder and health status of patients who have glenohumeral degenerative joint disease

We studied the effect of comorbidities on function of the shoulder and health status in a group of eighty-five consecutive patients who had glenohumeral degenerative joint disease of sufficient severity to meet one surgeon's criteria for the performance of shoulder arthroplasty. A questionnaire was used to identify the comorbidities, such as other diseases, social factors, or a work-related injury, for each patient. The number of functions on the Simple Shoulder Test that the patient could perform had a significant negative correlation with the number of comorbidities (r = -0.32, intercept = 4.6 per cent, slope = -0.6, and p = 0.0031). Each parameter on the Short Form-36 (except for physical role function) had a significant negative correlation with the number of comorbidities (p < 0.05). This negative relationship was strongest for general health perception (r = -0.42) and vitality (r = -0.35). We concluded that the number of comorbidities has a quantitative effect on function of the shoulder. In the evaluation of the functional status of patients and the effectiveness of treatment, the effects of comorbidity must be controlled. The results of the present study demonstrate that the scores on the Short Form-36 are quantitatively related to the number of comorbidities. The six parameters that are unrelated to function of the shoulder (physical function, social function, emotional role function, mental health, vitality, and general health perception) may provide a practical way to integrate the effects of all potential comorbidities on individual patients. Future clinical research will be strengthened by efforts to measure the impact of comorbidities and by strategies to control for their effects.

Immunization of cows with ferric enterobactin receptor from coliform bacteria

The serum and milk immunoglobulin (Ig) G responses of lactating dairy cows were determined following immunization with ferric enterobactin receptor FepA. Escherichia coli 471 was cultured in iron-depleted medium, and outer membrane proteins were extracted by 2% N-lauroylsarcosine sodium salt and 2% Triton X-100. The FepA was isolated from the outer membrane proteins by ion-exchange chromatography. Twenty cows were assigned to four treatment groups of 5 cows blocked by breed and days in milk. Treatment groups were vaccinated with 100 micrograms of FepA, 500 micrograms of FepA, Escherichia coli J5 bacterin, or sterile phosphate-buffered saline. Primary immunization was at approximately 200 d in milk, and booster immunizations were given 14 and 28 d later. Serum and whey IgG titers to FepA in cows vaccinated with FepA were significantly higher than those from cows vaccinated with either E. coli J5 bacterin or phosphate-buffered saline. Serum and whey IgG titers to FepA were elevated by 14 d in cows vaccinated with FepA. Significant differences were not observed between doses of FepA. The degree of cross-reactivity of purified IgG from cows vaccinated with FepA to E. coli and Klebsiella pneumoniae isolates was significantly higher than that to a control isolate that lacked FepA production. Immunization with FepA elicited an immunological response in serum and milk.

Total shoulder arthroplasty versus hemiarthroplasty. Current trends

Currently, a debate exists regarding the indications for hemiarthroplasty and total shoulder arthroplasty. A number of factors are important in making this decision. The article discusses some of the variables related to choosing the appropriate procedure for every patient. The authors also discuss their approach to various arthritic conditions of the shoulder, the rationale behind their approach, and their results. Future work will be necessary before more definitive recommendations can be made, and they may well be different for each individual surgeon.

Exploring the potential of problem-based learning in nurse education

It could be argued that the role of the nurse is beginning to change from that of a medical assistant to one of a more research-aware, reflective professional. As a result, the education of nursing students has needed to adapt. This paper explores how problem-based learning (PBL) may be an appropriate means of achieving an educational preparation that can respond to changing needs. Particular attention is paid to the theoretical underpinnings of PBL, especially the concepts of adult education, cognitive processes and learning in context. Some of the relevant empirical studies are reviewed, and the authors attempt to identify the gaps in the literature, concluding by recommending a course of action to expand the existing levels of understanding and evidence that supports, or otherwise, the use of PBL.

Tissue repair of the epidermis and dermis

Wounds of the skin heal in a predictable fashion and at a fairly constant rate if impediments to healing can be avoided. For the skin wound of the hand, the therapist and surgeon face paradoxic demands to balance optimal immobilization for wound healing with optimal motion for function. As long as the wound remains stable, therapy can begin very early in the postoperative period without interruption of the wound-healing process.

What is learned about nontarget items in simple visual search?

Human sensitivity to correlational structure between nontargets and likelihood of target presence in a visual letter-search task were studied in two experiments. In each of these experiments, the performance of subjects for whom the nontarget information was altered in the final trial block was compared with the performance of subjects for whom the nontarget information did not change. When stimulus strings were presented individually on a computer screen and subjects were required to make a yes-no decision about target presence (Experiment 1), the change in nontarget structure resulted in increased reaction times for target-absent trials. When subjects searched simultaneously for three possible targets (Experiment 2), the change in nontarget structure produced increased error rates and increased reaction times for both target-absent and target-present trials. Correlations between the amount of predictive information in individual stimulus strings and reaction times also showed that both switching and nonswitching subjects were sensitive to the nontarget context. However, neither self-reports of strategy nor postexperiment choices between context-consistent and-inconsistent letter strings indicated any explicit knowledge of the predictive information in the nontarget stimuli. Subjects can thus acquire and benefit from, apparently without awareness, information about subtle correlational structure in nontarget elements in simple visual search.

'The buck stops here': accepting responsibility for learning and actions after graduation from a problem-based learning nursing education curriculum

Despite the increased attention that problem-based learning has received as an appropriate pedagogical technique for educating adults for professional practice, reports that evaluate the process are rare and usually relate to professions other than nursing. A study was undertaken in order to discover the graduates' own perceptions of a problem-based learning programme and its effectiveness in preparing them for the reality of their chosen profession. Twelve practising graduate nurses who had completed the programme were interviewed according to the ethnographic method. Three categories were identified from the data: 'and all of a sudden...', which describes the transition from PBL student to staff nurse; 'not an unthinking assistant', where the characteristics that the PBL graduates believe make them different from traditionally trained nurses are described; and 'the buck stops here', which describes the sense of personal responsibility that the graduates experience in terms of their learning and actions.

Inhibition of in vitro growth of coliform bacteria by a monoclonal antibody directed against ferric enterobactin receptor FepA

The ability of a murine monoclonal antibody that blocks the enterobactin ligand-binding site of the ferric enterobactin receptor FepA to inhibit the growth of coliform bacteria derived from a bovine intramammary infection (IMI) was determined in an iron-restricted medium. Bacterial isolates from bovine IMI in five herds were tested by the chrome azurol sulfonate assay to detect siderophore production. Each of the isolates of Escherichia coli (n = 25) and Klebsiella pneumoniae (n = 25) were positive for siderophore production. Each isolate expressed iron-regulated outer membrane proteins when grown in trypticase soy broth plus the iron chelator alpha-alpha'-dipyridyl. Immunoblots revealed that the monoclonal antibody recognized FepA that was expressed by each of the E. coli isolates (n = 25). Only 4 of 25 K. pneumoniae isolates produced FepA that reacted with the monoclonal antibody. This result coincided with the results of an in vitro growth assay. Growth of all E. coli isolates was significantly inhibited by the addition of monoclonal antibody to synthetic medium containing apolactoferrin. Antigenic variation in the enterobactin-binding site resulted in a low percentage of K. pneumoniae isolates that were inhibited by the monoclonal antibody. Inhibition of bacterial growth by the monoclonal antibody was dose-dependent. As little as 50 micrograms/ml of purified antibody had an inhibitory effect on bacterial growth in the synthetic iron-restricted medium. Monoclonal antibody specific for the enterobactin ligand-binding site of FepA inhibited the growth of E. coli that was isolated from bovine IMI.

Reproducibility of antibiogram of bovine mammary gland staphylococci under conditions of repeated subculturing

The reproducibility of antibiogram profiles of 10 staphylococcal isolates of bovine mammary gland origin was tested under conditions of repeated subculturing. Prototype (original or index) antibiogram profiles were determined by subculturing these isolates from stock cultures stored at -70 degrees C. The isolates were then subcultured four times on blood agar and antibiogram profiles determined at each subculture on Mueller-Hinton agar. The antibiogram profiles of each isolate at each subculture were compared with the prototype profiles of that isolate. At repeat antibiogram determinations, deviations of < or = 5 mm in the individual zones of inhibition of penicillin, ampicillin and streptomycin from the prototype antibiogram profiles, resulted in a shift of only three isolates from the resistant to intermediate and one isolate from intermediate to resistant status of antibiotic susceptibility classification. It is suggested that in the interpretation of antibiogram, susceptibility classification (resistant, intermediate, or susceptible) variations accruing from a few millimetres differences in the diameter of the zones of inhibition should probably be disregarded.

Local circuit abnormalities in chronically epileptic rats after intrahippocampal tetanus toxin injection in infancy

In vitro slice experiments were undertaken in adult rats to investigate the physiological origins of a chronic epileptic condition that was initiated in infancy. A unilateral injection of a minute quantity of tetanus toxin into hippocampus on postnatal day 10 produced a severe convulsive syndrome characterized by brief but repeated seizures that lasted for 5-7 days. Hippocampal slices were then taken from these rats in adulthood because at this time previous studies have shown the occurrence of electrographic and behavioral seizures. Dramatic alterations in local circuit functioning were observed. In normal artificial cerebrospinal fluid (ACSF), spontaneous epileptiform network bursts were recorded in a majority (73%) of experimental rats. Network bursts occurred in area CA3 of both the injected and contralateral hippocampus. These consisted of intracellular depolarization shifts that were coincident with extracellularly recorded network bursts. Often they occurred at frequencies of 0.05-0.1 Hz and although variable in amplitude and duration, had all-or-none-like qualities. These events appeared to arise largely from local circuits in the CA3C subfield. Network bursts were rarely recorded in area CA1 and were never observed in the dentate gyrus. However in 31% of rats, a novel, higher frequency (2-8 Hz) field potential was recorded in area CA1. This was coincident with rhythmic, intracellularly recorded, inhibitory postsynaptic potentials (IPSPs). These summated IPSPs blocked action potential firing and reversed polarity near -75 mV. To understand the origins of network bursting in area CA3C, comparisons were made of the fundamental neurophysiological properties of pyramidal cells in epileptic and control rats. Of the passive and active membrane properties examined, all appeared normal. Unusually prolonged bursts of action potentials were observed in a small subset of pyramidal cells. However on average the duration of intrinsic bursts were unaltered in the CA3 neurons analyzed from experimental rats. To explore the role that alterations in CA3 recurrent excitatory network excitability may play in epileptiform discharges, picrotoxin was bath applied. On blockade of gamma-aminobutyric acid (GABAA) receptors, slices from experimental rats underwent prolonged electrographic seizures that were up to 10 s in duration. In contrast, slices from control rats produced only brief 100-ms network bursts. These results suggest that a change in excitability within CA3C recurrent excitatory networks likely contributes to seizures in chronically epileptic rats. However, at the same time, this hyperexcitability is controlled to an important degree by functional GABAA-mediated synaptic inhibition.

Bereavement and loss in childhood

This article examines the process of bereavement, its clinical presentation, and developmental influences. Family bereavement issues are outlined, pathologic and traumatic bereavement are described, and treatment strategies are suggested.

Concentrations of alpha-Tocopherol after intramammary infusion of Escherichia coli or lipopolysaccharide

Fifteen Holstein cows were used in a trial involving intramammary challenge to determine the effects of acute clinical mastitis on the concentrations of alpha-tocopherol in milk and plasma and the concentrations of neutrophils in milk and blood. Cows were assigned to one of three experimental groups challenged by intramammary infusion of lipopolysaccharide, Escherichia coli, or sterile phosphate-buffered saline. All quarters infused with lipopolysaccharide or E. coli were diagnosed with clinical mastitis on d 1 and 2 after challenge. Acute inflammation caused by intramammary infusion of lipopolysaccharide or E. coli resulted in increased concentrations of alpha-tocopherol in milk in challenged quarters but had no effect on concentrations of alpha-tocopherol in plasma. Concentrations of alpha-tocopherol in milk and blood neutrophils did not differ among treatment groups. Concentrations of alpha-tocopherol did not differ between milk and blood neutrophils. Approximately 25% of the alpha-tocopherol in milk from glands with clinical mastitis was associated with neutrophils, and < 10% of the alpha-tocopherol in milk from nonmastitic glands was associated with neutrophils. A shift toward sources of alpha-tocopherol other than synthesized milk fat occurred during acute inflammation in the mammary gland.

Responses of antibody titers to intramammary immunization with Escherichia coli J5 bacterin

The effect of an immunization schedule on responses of antibody titers was tested following vaccination with an Escherichia coli J5 bacterin. Eighteen cows were equally distributed among three immunization schedules: 1) subcutaneous injection at 14 d prior to the end of lactation, intramammary immunization at 7 d after drying off, and subcutaneous injection at 30 d into the dry period; 2) subcutaneous injections at drying off, at 30 d into the dry period, and within 12 h after calving; and 3) unimmunized controls. The E. coli J5 bacterin consisted of 5 ml of 10(9) boiled cells/ml of 0.9% NaCl plus 0.005% phenol emulsified with 5 ml of Freund's incomplete adjuvant. Subcutaneous injections were administered on the upper part of the rib cage, posterior to the scapula. Intramammary immunizations of 2.5 ml of bacterin were infused via the teat canal into each of the four mammary glands. Intramammary immunization increased rectal temperatures at 12 h after infusion, but subcutaneous injections did not induce febrile responses. Intramammary immunization enhanced immunoglobulin G titers in serum and whey on d 0 of lactation compared with subcutaneous immunizations. Immunoglobulin G titers in serum also were greater at d 30 of the dry period and at d 14 and 21 of lactation for cows that received intramammary immunization than for cows that were vaccinated by subcutaneous injections only. Immunoglobulin M titers in whey and serum on d 21 of lactation were greater for cows that received intramammary immunizations than for cows that were immunized by subcutaneous injections only.

Computer-delivered modeling of exposure for spider phobia: relevant versus irrelevant exposure

Spider phobic subjects (n = 45) completed 3 x 40 minute computer-delivered treatment sessions. Questionnaire ratings of phobic severity were completed pre- and posttreatment (n = 45) and 6-12 month follow-up (n = 38). The program used interactive animations to model self-exposure treatment methods. Subjects were randomized to one of three treatment groups (n = 15), each receiving a different version of the program. These treatment conditions were relevant exposure with feedback (REF), relevant exposure with no feedback (RENoF), or irrelevant exposure with feedback (IEF). Relevant exposure modeled exposure to spiders, irrelevant exposure to elevators. All groups showed significant phobic improvement following the treatment, as measured on a variety of instruments. Learning on the programs was demonstrated by a significantly increased performance (time taken to reach a target score) within each group across the three computer treatment sessions. Outcome was not significantly affected either relevance of exposure or the manipulation of the onscreen feedback. Subjects' report of exposure treatment undertaken at home correlated positively with phobic improvement.

Bacteria counts in sawdust bedding

Bacteria counts in untreated sawdust bedding were compared with those in sawdust bedding after the addition of lime and after daily replacement of bedding in the back one-third of the stalls. Addition of 1 kg of lime to 10 kg of sawdust reduced Gram-negative bacteria, coliforms, Klebsiella spp., and streptococci prior to use as bedding. Sawdust treated with lime also showed decreased bacteria counts compared with bacteria counts for sawdust that was replaced daily and compared with bacteria counts for control bedding after 1 d in the stall. The decrease in bacterial populations was related to an increase in bedding pH. Mean pH in the sawdust treated with lime was greater prior to use and after 1 d in the stall than the pH of other treatments. After 2 and 6 d in stalls, however, bacteria counts and pH were similar among treatments. Dry matter content of bedding did not differ among bedding treatments. Bacteria counts in bedding were positively correlated with teat skin swabs. Gram-negative bacteria and Klebsiella spp. counts on teat swabs were lower for cows housed on bedding treated with lime on d 2 compared with those for cows housed on control bedding and bedding that was replaced daily. Addition of lime to sawdust in the back one-third of tie stalls caused a decrease in exposure of teats to environmental mastitis pathogens in bedding for 1 d. Daily replacement of bedding had a minimal effect on bacteria counts in bedding and on teat skin.

Effect of vitamin E supplementation in diets with a low concentration of selenium on mammary gland health of dairy cows

Sixty-six cows and heifers (Holsteins and Jerseys) were assigned to one of three treatments at 60 d before anticipated calving. Treatment 1 consisted of 100 IU/d of supplemental vitamin E during the dry period and 100 IU/d during the first 30 d of lactation. Treatment 2 was 1000 IU/d of vitamin E during the dry period and 500 IU/d during lactation. Treatment 3 was 1000 IU/d of vitamin E during the first 46 d of the dry period, 4000 IU/d during the last 14 d of the dry period, and 2000 IU/d during lactation. Plasma concentrations of alpha-tocopherol decreased at calving for cows fed dietary treatments with low or intermediate concentrations of vitamin E, but not for cows fed the high vitamin E treatment. High dietary vitamin E increased concentrations of alpha-tocopherol in blood neutrophils at parturition, but no difference was found for the other two treatments. The percentage of quarters with new infections at calving was not different (32.0%) between cows receiving treatments that contained low and intermediate concentrations of vitamin E but was reduced (11.8%) in cows receiving the high vitamin E treatment. Clinical mastitis affected 25.0, 16.7, and 2.6% of quarters during the first 7 d of lactation for cows receiving the low, intermediate, and high vitamin E treatments, respectively. Cows with plasma concentrations of alpha-tocopherol < 3.0 micrograms/ml at calving were 9.4 times more likely to have clinical mastitis during the first 7 d of lactation than were cows with plasma concentrations of alpha-tocopherol > 3.0 micrograms/ml.

Axonal remodeling during postnatal maturation of CA3 hippocampal pyramidal neurons

Anatomical substrates were investigated for local circuit hyperexcitability that occurs in the CA3 subfield of the rat hippocampus during postnatal week 2. A transient excess of excitatory local circuit connectivity was hypothesized to underlie this hyperexcitability. To test this hypothesis, recurrent excitatory axon arbors from single biocytin-filled CA3 pyramidal cells were reconstructed. Arbors were analyzed in segments of area CA3 comparable in size to in vitro minislice preparations, which were shown to reproduce the developmental hyperexcitability seen in intact slices during postnatal week 2. Segments were then adjusted for hippocampal growth, based on age-dependent changes in neuron density in stratum pyramidale. Axon arbors were found to be short and possessed very few branches during the first postnatal week. By the second postnatal week, arbors had undergone dramatic growth and were much longer and more complex in their branching patterns. By adulthood, a significant decrease in all measures of arbor length and complexity was observed. Following growth adjustment, measures of axon length and varicosity number during week 2 were not significantly different from that of adulthood. However, the number of axon branches decreased by 50%. These results suggest that, during early postnatal life, there is exuberant outgrowth of local CA3 recurrent axons, and with maturation these recurrent collaterals are remodeled. Short-ranging, profusely branched axons appear to be replaced by longer-ranging arbors that possess fewer branches. Maturational changes in the dendritic location rather than the number of early-formed recurrent excitatory synapses may explain developmental hyperexcitability of the hippocampal CA3 subfield.

Dietary vitamin E and selenium affect mastitis and milk quality

Vitamin E and selenium (SE) are essential nutrients that are integral components of the antioxidant defense of tissues and cells. Soils in many of the important dairy regions of the world are Se-deficient, and feedstuffs grown on these soils will not provide adequate dietary Se. Cattle consuming stored forages are likely to be low in vitamin E unless supplemented, and vitamin E deficiencies are frequently observed in peripartum dairy cows. Many new intramammary infections (IMI) occur in the 2 wk before and after calving. Deficiencies of either vitamin E or Se have been associated with increased incidence and severity of IMI, increased clinical mastitis cases, and higher somatic cell counts (SCC) in individual cows and bulk tank milk. Somatic cell counts are a primary indicator of mastitis and milk quality in dairy herds. The polymorphonuclear neutrophil (PMN) is a major defensive mechanism against infection in the bovine mammary gland. A know consequence of vitamin E and Se deficiency is impaired PMN activity and postpartum vitamin E deficiencies are frequently observed in dairy cows. Dietary supplementation of cows with Se and vitamin E results in a more rapid PMN influx into milk following intramammary bacterial challenge and increased intracellular kill of ingested bacteria by PMN. Subcutaneous injections of vitamin E approximately 10 and 5 d before calving successfully elevated PMN alpha-tocopherol concentrations during the periparturient period and negated the suppressed intracellular kill of bacteria by PMN that commonly is observed around calving.

A comparison of patients with late-stage rheumatoid arthritis and osteoarthritis of the shoulder using self-assessed shoulder function and health status

OBJECTIVE

To compare the function and health status of individuals with advanced rheumatoid arthritis (RA) and osteoarthritis (OA) of the shoulder using standardized patient self-assessment tools.

METHODS

A group of patients with late-stage arthritic involvement of the shoulder was evaluated at the time of initial presentation using 2 questionnaires, one focusing on shoulder function and other on overall health status.

RESULTS

There was substantial variability in the shoulder function and health status within each diagnostic group; however, both groups demonstrated significant deficits in their Simple Shoulder Test responses and in many of their Health Status Questionnaire-Short Form 36 scores. While the patients with RA tended to have somewhat greater impairment of shoulder function, many of the differences were not statistically significant. By contrast, most health status parameters were significantly more impaired in the patients with RA.

CONCLUSIONS

Among patients with late-stage shoulder arthritis, the overall health status of those with RA is significantly worse than those with OA. Differences in health status may be important in selecting the optimal management for individual patients with late-stage shoulder arthritis. Self-assessment questionnaires are effective in characterizing these differences.

Anatomical properties of fast spiking cells that initiate synchronized population discharges in immature hippocampus

Minislices of the CA3 hippocampal subfield were prepared from 10- to 15-day-old rats and exposed to penicillin, a GABAA receptor antagonist. Synchronized population discharges occurred spontaneously but could also be entrained by action potentials in single, fast spiking cells. This was unexpected, since fast spiking cells in the hippocampus are normally thought to be inhibitory interneurons. Experiments were thus undertaken to determine the anatomical identity of these cells. Biocytin injections showed that these cells had the anatomical feature of inhibitory interneurons. Two classes of cells were identified: basket cells (including cells with pyramidal or multipolar dendritic arbors) and bistratified cells. Basket cells had characteristic dense axonal arbors in the stratum pyramidale. They also possessed wide ranging axons in strata radiatum and oriens. The axons of bistratified cells avoided the cell body layer and produced a web-like plexus of axons in strata radiatum and oriens. In the majority of minislices, dye coupling was also observed. Interneurons were preferentially dye-coupled to other interneurons. We speculate that, in early life, hippocampal interneurons may have dualistic synaptic properties. Normally, they inhibit nearby pyramidal cells; however, when GABAA receptors are suppressed a secondary excitatory property of these cells is uncovered.

Isotype-specific antibody responses to rotavirus and virus proteins in cows inoculated with subunit vaccines composed of recombinant SA11 rotavirus core-like particles (CLP) or virus-like particles (VLP)

The isotype antibody responses to bovine IND P5, G6 and simian SA11 P2, G3 rotavirus and SA11 rotavirus proteins (VP4, VP6 and VP7) in serum, colostrum and milk were analysed by ELISA in three groups of vaccinated cows and nonvaccinated controls. Pregnant cows were vaccinated intramuscularly and intramammarily with recombinant baculovirus-expressed SA11 rotavirus VLP (triple-layered virus-like particles containing rotavirus VP2, VP4, VP6 and VP7); CLP (double-layered core-like particles containing rotavirus VP2 and VP6); or inactivated SA11 rotavirus, respectively. Rotavirus antigen titers were highest (30-200-fold) in ELISA in the VLP vaccine compared to the inactivated SA11 vaccine. The IgG1, IgG2 and IgM geometric mean antibody titers (GMT) to rotavirus (titers to bovine rotavirus vs SA11 rotavirus did not differ significantly for any isotype or group) and the IgG2 GMT to VP6 in serum at calving in the vaccinated groups were significantly (P < 0.05) higher than in the control group. In colostrum, IgG1 and IgA rotavirus antibody titers were significantly elevated for VLP (IgG1 GMT 832225; IgA GMT 16384), CLP (IgG1 GMT 660561; IgA GMT 10321) and SA11 (IgG1 GMT 131072; IgA GMT 1448) vaccinated cows compared to control cows (IgG1 GMT 11585; IgA GMT 45). The IgG1 and IgA GMT to rotavirus were significantly elevated (6-100-fold) in milk of VLP and CLP vaccinated cows compared to SA11 vaccinated or control cows. The isotype antibody responses to VP6 in serum, colostrum and milk paralleled the responses to rotavirus, but titers were approximately 2-10-fold lower. Only cows vaccinated with VLP had significantly enhanced serum, colostral and milk antibody titers to rotavirus VP4 and VP7. These results demonstrate that rotavirus antibody titers in serum, colostrum and milk are significantly enhanced by use of non-infectious VLP, CLP and inactivated SA11 rotavirus vaccines, but the VLP or CLP vaccines induced the highest antibody responses, corresponding to their higher rotavirus antigen titers measured by ELISA.

Adenovirus-mediated gene transfer into dissociated and explant cultures of rat hippocampal neurons

Genetic manipulation offers great potential for studying the molecular and cellular processes which control or regulate the complex developmental properties of neurons. Gene transfer into neurons, however, is notoriously difficult. In this study we have used a replication-defective adenovirus (Adv/RSV beta gal), expressing beta-galactosidase (beta-gal) as a reporter gene, to infect dissociated cultures of rat hippocampal neurons and hippocampal slice cultures. Because future studies will require either long-term (e.g., developmental) or short-term (e.g., electrophysiological) expression of recombinant genes in neuronal cultures, we have optimized infection conditions for each situation. The Adv/RSV beta gal construct infects neurons and glial cells equally well, with no apparent alterations in cellular morphology. In slice cultures, the same efficiency and temporal control of beta-gal expression following Adv/RSV beta gal infection was achieved. Focal application of the adenoviruses, by microinjection, permitted infection of discrete subregions within the hippocampal explants. Whole cell recordings of dissociated hippocampal neurons and field recordings from the explant cultures, infected with Adv/RSV beta gal at low multiplicities of infection, indicated no significant alteration in the electrophysiological profiles of neurons in these cultures. The results demonstrate the utility of adenoviruses as gene transfer vectors for primary cultures of neurons. Adenovirus-mediated gene transfer into slice cultures also provides an opportunity to study development or plasticity in an environment where the circuitry and cytoarchitecture of the tissue are preserved and the areas of genetic manipulation can be spatially isolated.

alpha-Tocopherol concentrations in milk and plasma during clinical Escherichia coli mastitis

Eighteen cows were challenged by intramammary infusion with Escherichia coli 727 to determine the effects of acute clinical mastitis on alpha-tocopherol concentrations in plasma and milk. Cows were fed diets supplemented with 1000 IU of vitamin E/d from calving through the experimental period. At challenge, geometric mean DIM was 33 d. Each mammary quarter was diagnosed with an IMI and clinical mastitis at 24 and 48 h after challenge. The alpha-tocopherol concentrations in milk from challenged quarters were approximately 60% greater by 24 and 48 h after challenge than concentrations at prechallenge and 168 h postchallenge. Plasma alpha-tocopherol concentrations did not change after intramammary challenge. The alpha-tocopherol in plasma and milk was correlated at 48 and 168 h postchallenge but not at prechallenge or 24 h postchallenge. Milk alpha-tocopherol and SCC were correlated positively across all sample periods. Milk fat and milk alpha-tocopherol concentrations were correlated at each sample period except 24 h postchallenge. Increases in milk alpha-tocopherol during clinical mastitis were not correlated to milk production, DMI, or BSA concentration in milk. Changes in milk alpha-tocopherol concentration during clinical mastitis were similar to the dynamics of milk SCC.

Differential recovery from impairment to the phonological lexicon

Word production was examined in four aphasics diagnosed acutely with neologistic jargon and who displayed impairment to the lexical stage of phonological production (Kohn & Smith, 1993, 1994a). To investigate the major source of their nonword errors (i.e., neologisms, phonemic paraphasias), single word production was tested at three different times over the first 6 months postonset, with one subject receiving additional testing at 14 months postonset. Two subjects showed signs of recovery to the phonological output system with respect to: (1) improved word production scores, (2) increased frequency of phonemic paraphasias versus neologisms, and (3) increased production of target phonemes. These subjects also displayed above-chance production of target phonemes and no significant tendency to perseverate phonemes across picture-naming trials. It was argued that this pattern reflects a resolving disturbance in retrieving entries from the phonological lexicon. The other two subjects showed no improvement in word production. They also consistently produced target phonemes at chance levels and had a tendency to perseverate phonemes across picture-naming trials. This static pattern of performance was considered to reflect loss of information from the phonological lexicon. The neuroanatomical damage sustained by each case was consistent with these two recovery patterns.

Consonant harmony as a compensatory mechanism in fluent aphasic speech

This study addresses how fluent aphasics construct complete phonological representations, given the premise that their phonological speech errors result from faulty information about stored lexical representations. We explored whether consonant harmony, a common rule-governed process of feature copying, operates as a compensatory device for completing phonological representations in fluent aphasia. This was examined in a corpus of phonemic paraphasias (n = 543) produced by 8 fluent aphasics during picture naming. Consonant substitutions due to a single feature change (n = 143) were analyzed for the properties of consonant harmony predicted by the phonological principles embodied in a Universal Markedness version of Underspecification Theory (e.g., Chomsky and Halle, 1968). Results indicated that harmony constrained the feature substitution errors involving the feature class of voice (e.g., calendar-->/[symbol: see text]/), but not place of articulation (e.g., igloo-->/idlu/); substitutions due to an error in manner were rare. These findings were used to argue that for English-speaking fluent aphasics a consonant harmony rule for the feature voice is incorporated into a compensatory output mechanism that is used to complete faulty lexical-phonological representations.

Antigenic crossreactivity and lipopolysaccharide neutralization properties of bovine immunoglobulin G

We investigated a possible mechanism by which immunization against core and lipid A determinants of lipopolysaccharide reduced clinical cases of mastitis and symptoms commonly associated with heterologous Gram-negative IMI. The IgG fraction of sera from cows immunized with either Escherichia coli J5 bacterin, E. coli J5 lipopolysaccharide conjugate vaccine, or unimmunized controls was purified by precipitation with caprylic acid and ammonium sulfate. The degree of IgG crossreactivity with Gram-negative bacteria that were isolated from clinical quarters was greater than that with Gram-positive isolates of Staphylococcus aureus. The highest magnitude of crossreactivity was against smooth strain E. coli isolates, followed by heterologous species of Enterobacter, Serratia, and Klebsiella isolates. Serum IgG from cows immunized with conjugate was highly crossreactive to E. coli J5, E. coli O111:B4, Serratia marcescens, Klebsiella pneumoniae, and Salmonella typhimurium lipopolysaccharides. The magnitude of antibody crossreactivity with lipopolysaccharides coincided with the ability of IgG to suppress the mitogenic effect of lipopolysaccharides on bovine lymphocytes.

Aetiology of spider phobia: classificatory differences between two origins instruments

The origins of fear of spiders was investigated in 33 spider phobic Ss entering a treatment study. All Ss completed Menzies and Clarke's (1993a) Origins Questionnaire (OQ) (Behaviour Research and Therapy, 31, 355-365) and Ost and Hugdahl's (1981) Phobic Origins Questionnaire (POQ) (Behaviour Research and Therapy, 19, 439-447). The results for the individual questionnaires were similar to those reported in previous studies. However a comparison of assignments of origin category for the two questionnaires showed widely discrepant results. The POQ returned 17 positive responses for classical conditioning, the OQ only 2. By contrast the OQ returned 10 origins as 'non-conditioning traumatic event', 9 of which returned positive responses for classical conditioning on the POQ. A further 15 Ss on the OQ were categorised as 'always been this way', the preponderance of these being classified as vicarious or informational in origin on the POQ. The POQ does not have a specific question or category for non-associative acquisition of phobias. The results of the origins assignments are detailed and their relation to the structure and questions of the questionnaires is outlined. Past studies using the POQ have produced results supporting acquisition of a substantial proportion of phobias by classical conditioning. The findings of this study suggest that such results mainly reflect inherent bias in that instrument.

Environmental streptococcal intramammary infections of the bovine mammary gland

Characteristics of environmental streptococcal IMI were investigated over a 7-yr period for a herd in total confinement. A total of 374 new environmental streptococcal IMI was detected. Approximately 50.5% of IMI were new in the dry period, and 49.5% were new in lactation. The rate of new IMI was .00312 IMI/cow day during the dry period and .00054 IMI/cow day during lactation. The percentages of cows and quarters with an environmental streptococcal IMI present at calving were 10.6 and 3.2%, respectively. The percentage of heifers with an environmental streptococcal IMI at calving was similar to that for cows. The rate of new environmental streptococcal IMI was greater during the 1st mo of lactation than during the remainder of lactation. The rate of IMI during late lactation was higher for older cows than for either heifers or cows in second lactation. The rate of environmental streptococcal IMI during the dry period and during lactation was greatest during summer. The mean days of lactation that cows were infected for all IMI was 12.3 d. Approximately 41% of IMI had a duration of < 8 d. Stage of lactation, season of the year, and parity influenced the rate of new IMI.

Efficacy of a barrier teat dip containing .55% chlorhexidine for prevention of bovine mastitis

A natural exposure trial was conducted for 12 mo in a commercial herd of 125 lactating cows to compare the efficacy of an experimental barrier teat dip containing .55% chlorhexidine gluconate with the efficacy of a 1% iodophor for preventing new IMI and clinical mastitis. Teats of half of the cows were dipped in the experimental barrier product, and teats of the remaining half of the herd were dipped in the 1% iodophor product. Quarters dipped with the experimental barrier product had fewer new IMI caused by Escherichia coli, coagulase-negative staphylococci, or Gram-positive bacilli than did quarters dipped in the 1% iodophor. Incidence of new IMI caused by Serratia spp. and Pseudomonas spp. was greater for quarters dipped in the experimental barrier product than for quarters dipped in the 1% iodophor. Efficacy of the two teat dips against new IMI caused by Staphylococcus aureus, environmental streptococci, and Klebsiella spp. did not differ. Incidence of bacteriologically negative clinical cases of mastitis was greater in quarters dipped in the 1% iodophor than in quarters dipped in the experimental barrier product. Incidence of clinical mastitis cases caused by Staph. aureus, environmental streptococci, E. coli, Klebsiella spp., Serratia spp., and Pseudomonas spp. did not differ between treatment groups.

Immunization of dairy cows with an Escherichia coli J5 lipopolysaccharide vaccine

Development of a lipopolysaccharide-protein conjugate vaccine and the immunological response to the vaccine were investigated. Lipopolysaccharide derived from Escherichia coli J5 was detoxified by mild alkaline hydrolysis. Detoxification reduced endotoxin activity 2500-fold compared with that of native J5 lipopolysaccharide. The conjugate vaccine was synthesized by covalently coupling detoxified lipopolysaccharide to chicken serum albumin by reductive amination. Dairy cows were immunized with 8.35 mg of conjugate (n = 3) or 5 x 10(9) heat-killed J5 bacterin (n = 5) at 215 DIM and received a secondary immunization 14 d later. Control cows were not immunized. Immunization enhanced serum antibody titer to J5 lipopolysaccharide antigens. Whey IgG and IgM titers to J5 lipopolysaccharide were not different among treatment groups. Serum and whey IgG titers to J5 whole-cell antigens were elevated in immunized cows within treatment groups. Immunization did not enhance whey IgM to J5 whole-cell antigens. Conjugate immunization elicited an immune response comparable with or greater than that of immunized cows with J5 bacterin.

Diverse neuronal populations mediate local circuit excitation in area CA3 of developing hippocampus

1. Studies were undertaken to better understand why the developing hippocampus has a marked capacity to generate prolonged synchronized discharges when exposed to gamma-aminobutyric acid-A (GABAA) receptor antagonists. 2. Excitatory synaptic interactions were studied in small microdissected segments of hippocampal area CA3. Slices were obtained from 10- to 16-day-old rats. Application of the GABAA receptor antagonist penicillin produced prolonged synchronized discharges in minislices that were very similar, if not identical, to those recorded in intact slices. The sizes of minislices were systematically varied. Greater than 90% of those that measured 600 microns along the cell body layer produced prolonged synchronized discharges, whereas most minislices measuring 300 microns produced only brief interictal spikes. 3. Action potentials in the majority (75%, 158 of 254) of cells impaled with microelectrodes were able to entrain the entire CA3 population. They were also able to increase (on average 26%) the frequency of spontaneous population discharges. The population discharges were followed by a refractory period that lasted 5-60 s, during which single cells were unable to initiate a population discharge. 4. The majority (87%) of neurons with intrinsic burst properties were found to entrain the CA3 population. The electrophysiological characteristics of these cells were reminiscent of recordings obtained from more mature rats. Action potentials were quite prolonged and demonstrated a secondary shoulder or hump on the down-slope of the spike. 5. When bursting cells were filled with Lucifer yellow and imaged during recording sessions by videomicroscopy and later using confocal microscopy, they showed the anatomic features of CA3 hippocampal pyramidal cells. Confocal microscopy permitted detailed characterization of individual neurons and showed substantial variation in cellular microanatomy. 6. Another class of cells that were found to entrain the CA3 population but did not demonstrate intrinsic bursts were termed regular-firing cells. These cells possessed many of the anatomic and physiological features of bursting cells with the exception of burst firing. They were rarely encountered in intracellular recordings. 7. The third physiological class of cells was termed fast-spiking cells. These had action potentials that were shorter in duration than the other two cell types. They were distinct in the rapid rate of spike repolarization. They demonstrated modest degrees of spike frequency adaptation and fired repeatedly and at relatively high frequencies. Compared with reports on fast-spiking cells in mature hippocampus and neocortex, action potentials appear to be slower and repetitive discharging appeared to be of a lower frequency.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of forage to concentrate ratio on disappearance of vitamins A and E during in vitro ruminal fermentation

The effects of forage to concentrate ratio and the commercial form of vitamins A and E on in vitro ruminal disappearance of retinol and alpha-tocopherol were studied. Ruminally fistulated cows were fed diets with either 80 or 50% forage. In vitro substrates that were similar to those fed to the donor cows were incubated with buffered ruminal fluid for 24 h. Different commercial forms of vitamin E (spray-dried, silicic acid adsorbate, and lipid-encased forms) and vitamin A (gelatin beadlet and lipid-encased forms) were added to the flasks. The vitamin E was all-rac-alpha-tocopheryl acetate, and the vitamin A was all-trans-retinyl acetate. The amount of alpha-tocopherol in the flasks was not affected by diet or form of vitamin E and did not change over the 24-h incubation. Retinol disappearance was not affected by form of vitamin A but was substantially higher for the 50% forage diet than for the 80% forage diet (72 vs. 20% at 24 h). These data suggest that ruminal metabolism of vitamin E is minimal and not affected by forage to concentrate ratio. Additionally, vitamin A destruction in the rumen was much higher when cows were fed a typical lactation diet than when fed a typical dry cow diet.

Factors affecting serum selenium and vitamin E concentrations in dairy cows

Supplementation of selenium and vitamin E to enhance disease resistance in dairy cattle has become common, particularly to prevent periparturient reproductive disorders and mastitis. To establish reference values for serum vitamin E and selenium concentrations in postparturient dairy cattle and to determine whether serum concentrations of these micronutrients varied with season and stage of lactation, cows from a stratified random sample of 50 herds were studied for 1 year. Blood samples were collected from each of the 50 study herds twice, from the 10 most recently parturient cows or from 10% of the herd, whichever was greatest. Mean concentration of vitamin E and selenium was 2.55 micrograms/ml and 78.12 ng/ml, respectively. Vitamin E concentrations were significantly (P < 0.05) higher during the summer and fall than during the winter and spring. Selenium concentrations were significantly (P < 0.05) lower during the summer and fall than during the winter and spring. Herd, season of blood sample collection, and time since parturition were significant (P < 0.02) in explaining variation in vitamin E and selenium concentrations.