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Biomedical subjects

J A Harris

Publications and source records attributed to J A Harris.

At least 37 records · Page 2Linked to original sources
PubMed2000

Suprachiasmatic nucleus projections to the paraventricular thalamic nucleus in nocturnal rats (Rattus norvegicus) and diurnal nile grass rats (Arviacanthis niloticus).

The circadian pacemaker of the suprachiasmatic nucleus (SCN) is likely to control the timing of the sleep-wake cycle in mammals by modulating the daily activity patterns of brain regions important in sleep and wakefulness. One such brain region is the paraventricular nucleus of the thalamus (PVT). In both nocturnal rats and the diurnal rodent Arvicanthis niltoicus (Nile grass rat), expression of Fos (the product of the immediate-early gene c-fos) in the PVT increases at times of day when the animals are most active. To compare the projections of the SCN to the PVT in these two species, the retrograde tracer cholera toxin (beta subunit; CTbeta) was microinjected into the PVT and the SCN was examined to identify labeled neurons. Further, the PVT-projecting SCN cells containing either arginine vasopressin (AVP) or gastrin releasing peptide (GRP) were also compared between species. In both nocturnal rats and diurnal Nile grass rats, the SCN sends a substantial projection to the PVT. In both species, many PVT-projecting SCN neurons contain AVP, and few contain GRP. Other work has shown that some AVP-containing neurons of the SCN function differently in rats and Nile grass rats. Projections from functionally distinct SCN neurons to the PVT may contribute to the difference in the temporal distribution of sleep and wakefulness seen between these two species.

Animals↗
PubMed2000

Ipsilateral and contralateral transfer of tactile learning.

We examined the spatial organization of perceptual learning in a cortex-dependent task. Rats learned a tactile task using four whiskers on one side of the snout, all others being clipped. These trained whiskers were then clipped and prosthetic whiskers were attached. Subsequent performance was found to be determined by the location of the prosthetic whiskers. There was partial transfer of learning to neighbouring whisker positions. In addition, there was partial transfer of learning to whisker positions on the other side of the snout, but only if the prosthetic whiskers were symmetrically opposite the trained whiskers. These findings suggest that neural changes underlying perceptual learning are distributed according to the topographic organization of the sensory cortical map.

Animals↗
PubMed2000

Lymphoma arising in an S-pouch after total proctocolectomy for ulcerative colitis: report of a case.

The gastrointestinal tract is the most common extranodal site of primary non-Hodgkin's lymphoma. We present a case of a 50-year-old male with primary B cell lymphoma arising in an S-pouch eight years after a total proctocolectomy for ulcerative colitis. After chemoradiotherapy the patient remained asymptomatic, with an intact S-pouch. Pouch conservation is feasible in patients with primary lymphoma of the pouch, using chemoradiotherapy and close follow-up examinations.

Colitis, Ulcerative↗
PubMed2000

HIV postexposure prophylaxis for children and adolescents.

HIV postexposure prophylaxis (PEP) is now a well-established part of the management of health care workers after occupational exposures to HIV. Use of PEP for adults exposed to HIV after sexual contact or injection drug use in nonoccupational settings remains controversial with limited data available. There is even less information available concerning HIV PEP for children and adolescents after accidental needlestick injuries or sexual assault. The objective was to describe the current practice of and associated problems with HIV PEP for children and adolescents at an urban academic pediatric emergency department. A retrospective review of all children and adolescents offered HIV PEP between June 1997-June 1998 was conducted. Ten pediatric and adolescent patients were offered HIV PEP, six patients after sexual assault, four patients after needle stick injuries. There were two small children 2 and 3 years of age and eight adolescents. Of these 10 patients, eight were started on HIV PEP. The regimens used for PEP varied; zidovudine, lamivudine, and indinavir were prescribed for in seven patients and zidovudine, lamivudine, and nelfinavir for one other. All 10 patients were HIV negative by serology at baseline testing and all available for follow-up testing (5 of 10) remained HIV negative at 4 to 28 weeks. Only two patients completed the full course of 4 weeks of antiretroviral therapy. Financial concerns, side effects, additional psychiatric and substance abuse issues as well as the degree of parental involvement influenced whether PEP and clinical follow-up was completed. HIV PEP in the nonoccupational setting for children and adolescents presents a medical and management challenge, and requires a coordinated effort at the initial presentation to the health care system and at follow-up. The difficulties encountered in the patients in our series need to be considered before initiating prophylaxis. A provisional management approach to HIV PEP in children and adolescents is proposed.

Academic Medical Centers↗
PubMed2000

Motivational state regulates the content of learned flavor preferences.

Rats acquired a preference for an aqueous odor (almond) presented in simultaneous compound with sucrose. Separate presentations of saccharin reduced this preference in rats with ad-lib access to food during training or at test, but not in rats that were hungry during both training and test. In contrast, separate presentations of sucrose reduced the preference for the almond irrespective of deprivation state during training and test. We interpret the results to mean that a hungry rat forms odor-taste and odor-calorie associations, and its motivational state on test determines which of these associations controls the preference. In contrast, a rat that is not hungry during training only forms an odor-taste association, and its performance on test is independent of its level of hunger.

Animals↗
PubMed2000

Contextual control over conditioned responding in a latent inhibition paradigm.

We used 1-, 2-, and 3-context designs to study the control exerted by contexts over freezing in rats exposed to a conditioned stimulus (CS) in advance of its pairing with a shock unconditioned stimulus. The latent inhibition observed when preexposure, conditioning, and testing occurred in the same context was attenuated if preexposure occurred in a different context to conditioning and testing. Latent inhibition (i.e., attenuated performance) was restored in a CS-specific manner if preexposure and testing occurred in the same context and conditioning in a different one. Latent inhibition was also reduced by a long retention interval but remained specific for a particular context-CS relation. Finally, CS preexposure resulted in contextual control over the expression of excitatory conditioned performance. The results are discussed in terms of memory, associative, and associative-performance models of CS-preexposure effects.

Animals↗
PubMed2000

Contextual control over conditioned responding in an extinction paradigm.

Four experiments studied contextual control over rats' freezing to conditioned stimuli (CSs) that had been paired with shock and were then extinguished. In Experiment 1, rats were exposed to a CS A-shock and a CS B-shock pairing in Context C. CS A was then extinguished in Context A, and CS B in Context B. Freezing was renewed when each CS was presented in the context where the other CS had been extinguished. In Experiments 2-4, rats were exposed to a CS A-shock pairing in A and a CS B-shock pairing in B. They were then exposed to Context C where one, both, or neither of the CSs were extinguished, or where both CSs continued to be reinforced. On test, the rats froze more to CS A than to CS B in Context A, and more to CS B than to CS A in Context B, but only if the CSs had been extinguished. Thus, after extinction, rats use contexts to regulate retrieval not only of their memory for extinction, but also of their memory for the original conditioning episode.

Aged↗
PubMed2000

Effect of fibrin glue on lymphatic drainage after modified radical mastectomy: a prospective randomized trial.

Fibrin as a tissue sealant has been used since the turn of the century for hemostasis. The development of cryoprecipitate and the resultant availability of higher concentrations of fibrinogen have led to a resurgence of interest in this material. Fibrin glue has since been shown to be effective for numerous applications throughout the field of surgery. Animal studies have shown fibrin glue to be effective at reducing drain output after mastectomy. Human studies, however, have been equivocal. Our objectives were to determine whether the use of fibrin glue would decrease lymphatic drainage after modified radical mastectomy and subsequently reduce time to drain removal. A prospective randomized trial was conducted consisting of 27 women. All women received modified radical mastectomy. At the completion of the mastectomy they were randomized to receive either standard closure or the application of fibrin glue before standard closure. Patients were then monitored for daily drain output, time to drain removal, and wound complications. A total of 14 women received fibrin glue and 13 received no glue. Those patients receiving fibrin glue had a significantly higher average drain output than patients who did not receive glue (1308 vs 754 cm3; P = 0.012). Time to drain removal was also increased by 4 days, although this did not reach statistical significance. The overall complication rate was higher for the fibrin glue group, although again, this did not reach significance. The application of fibrin glue significantly increased drain total drain output after modified radical mastectomy. Time to drain removal was increased as was the complication rate. On the basis of these data fibrin glue cannot be recommended for routine use in modified radical mastectomy.

Breast Neoplasms↗
PubMed2000

CPT changes in 2000.

Explore the source record for details and available documents.

Abstracting and Indexing↗
PubMed1999

Distribution of tactile learning and its neural basis.

The brain's sensory processing systems are modified during perceptual learning. To learn more about the spatial organization of learning-related modifications, we trained rats to utilize the sensory signal from a single intact whisker to carry out a behavioral task. Once a rat had mastered the task, we clipped its "trained" whisker and attached a "prosthetic" one to a different whisker stub. We then tested the rat to determine how quickly it could relearn the task by using the new whisker. We observed that rats were immediately able to use the prosthetic whisker if it were attached to the stub of the trained whisker but not if it were attached to a different stub. Indeed, the greater the distance between the trained and prosthetic whisker, the more trials were needed to relearn the task. We hypothesized that this "transfer" of learning between whiskers might depend on how much the representations of individual whiskers overlap in primary somatosensory cortex. Testing this hypothesis by using 100-electrode cortical recordings, we found that the overlap between the cortical response patterns of two whiskers accounted well for the transfer of learning between them: The correlation between the electrophysiological and behavioral data was very high (r = 0.98). These findings suggest that a topographically distributed memory trace for sensory-perceptual learning may reside in primary sensory cortex.

Animals↗
PubMed1999

Requirements for infrastructure and essential activities of infection control and epidemiology in out-of-hospital settings: a Consensus Panel report.

In 1997 the Association for Professionals in Infection Control and Epidemiology and the Society for Healthcare Epidemiology of America established a consensus panel to develop recommendations for optimal infrastructure and essential activities of infection control and epidemiology programs in out-of-hospital settings. The following report represents the Consensus Panel's best assessment of requirements for a healthy and effective out-of-hospital-based infection control and epidemiology program. The recommendations fall into 5 categories: managing critical data and information; developing and recommending policies and procedures; intervening directly to prevent infections; educating and training of health care workers, patients, and nonmedical caregivers; and resources. The Consensus Panel used an evidence-based approach and categorized recommendations according to modifications of the scheme developed by the Clinical Affairs Committee of the Infectious Diseases Society of America and the Centers for Disease Control and Prevention's Healthcare Infection Control Practices Advisory Committee.

Allied Health Personnel↗
PubMed1999

The benzodiazepine midazolam does not impair Pavlovian fear conditioning but regulates when and where fear is expressed.

Rats were injected with a benzodiazepine (midazolam) and shocked after presentation of an auditory conditioned stimulus (CS). They were then tested for fear reactions (freezing) to the CS in either the original context or a 2nd context after either a short (1-day) or long (21-day) retention interval. Rats tested in the original context froze less after 1 day than rats tested after that interval in the 2nd context or rats tested after 21 days. Moreover, rats tested after the long interval in the original context froze less than rats tested after that interval in the 2nd context. Therefore, midazolam does not impair the acquisition of conditioned fear but regulates when and where that fear is expressed. These effects of midazolam were interpreted as a contextually controlled deficit in the expression of conditioned fear that is similar to that associated with latent inhibition and extinction (M. E. Bouton, 1993).

Animals↗
PubMed1999

Investigations by HPLC-electrospray mass spectrometry and NMR spectroscopy into the isomerisation of salinomycin.

HPLC-MS studies have indicated that certain polyether ionophore veterinary drugs are prone to degradation when stored as water-methanol solutions at ambient temperature. Salinomycin and narasin were particularly susceptible, disappearing completely within weeks to produce more polar species, which were identified as isomers of the original compounds. Lasalocid appeared to be stable under such conditions. Structural elucidation of the principal ultimate salinomycin isomerisation product was achieved by 2D NMR spectroscopy. This indicated that the isomerisation process consists of the opening of the spiro rings in the salinomycin structure with the concomitant formation of a furan moiety. The MS data indicated that the isomers retain the ability to complex alkali metal ions and may therefore retain their pharmacological activity. These discoveries may have implications both for the development of legislation covering acceptable levels of polyether ionophore residues in foodstuffs and also for analytical protocols designed to detect them.

Anti-Bacterial Agents↗
PubMed1999

Requirements for infrastructure and essential activities of infection control and epidemiology in out-of-hospital settings: a consensus panel report. Association for Professionals in Infection Control and Epidemiology and Society for Healthcare Epidemiology of America.

In 1997 the Association for Professionals in Infection Control and Epidemiology and the Society for Healthcare Epidemiology of America established a consensus panel to develop recommendations for optimal infrastructure and essential activities of infection control and epidemiology programs in out-of-hospital settings. The following report represents the Consensus Panel's best assessment of requirements for a healthy and effective out-of-hospital-based infection control and epidemiology program. The recommendations fall into 5 categories: managing critical data and information; developing and recommending policies and procedures; intervening directly to prevent infections; educating and training of health care workers, patients, and nonmedical caregivers; and resources. The Consensus Panel used an evidence-based approach and categorized recommendations according to modifications of the scheme developed by the Clinical Affairs Committee of the Infectious Diseases Society of America and the Centers for Disease Control and Prevention's Healthcare Infection Control Practices Advisory Committee.

Aftercare↗