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Biomedical subjects

J A Harris

Publications and source records attributed to J A Harris.

At least 19 recordsLinked to original sources
PubMed2003

Seroepidemiology of Toxoplasma gondii in dogs in Trinidad and Tobago.

A cross-sectional study was conducted to determine the seroprevalence of Toxoplasma gondii agglutinins and to investigate the relationship between various risk factors and occurrence of toxoplasmosis in dogs in Trinidad. Of a total 250 dogs, comprising domestic, hunting and stray dogs, 80 (32.0%) were positive for T. gondii agglutinins at a titre of > or =1:32 using a latex agglutination test. Stray dogs (60.5%) had statistically significantly higher (P<0.001) seroprevalence for toxoplasmosis than hunting dogs (30.5%) and domestic dogs (25.5%). Amongst dogs whose ages were known, the prevalence of toxoplasmosis was significantly highest (P=0.037) in dogs in the >2-3 years age group compared with other age groups. Dogs that consumed home-cooked foods had a seroprevalence of 32.9% compared with those fed commercial dog foods (17.2%) and dogs fed both home-cooked and commercial foods (21.0%). However, the difference was not statistically significant (P>0.05; chi(2)). The rather high prevalence of toxoplasmosis in stray dogs is a good indication of the extent of the infection in the environment.

Age Factors↗
PubMed2003

The epidemiology of cardiovascular defects, part 2: a study based on data from three large registries of congenital malformations.

There were three objectives of this study: to investigate possible specificity in the association between specific cardiac defects and chromosomal anomalies; to evaluate ways of categorizing cardiac defects into larger groups with epidemiological similarities that could indicate similarities in etiology or pathogenesis; and to analyze the relationship between specific cardiac defects and diabetes. We pooled data on infants (aged 1 year or younger) with congenital cardiovascular defects from three large birth defect registries in California, Sweden, and France. The registries in Sweden and France obtained data through reporting from various sources; in California, medical records were reviewed. For severe congenital heart defects, the percentage of infants with identified chromosomal anomalies varied between 0.9% for d-TGV to 68.4% for ECD. In general, specific cardiac conditions have different risk factors. For example, conotruncal defects have been traditionally grouped, but the data presented in this paper indicates more differences for risk factors for the components of conotruncal defects: tetralogy of Fallot, d-TGV, common truncus, and DORV. In general, we suggest the strategy of "splitting" rather than "lumping" when searching for specific genetic factors and/or teratogens. Adequate analysis thus requires large registries or collaboration among registries. The findings did not support constellations between mothers' diabetes and specific defects.

Abnormalities, Drug-Induced↗
PubMed2003

The epidemiology of cardiovascular defects, part I: a study based on data from three large registries of congenital malformations.

To analyze complex and noncomplex cardiac malformations regarding prevalence and in relation to demographic variables, we pooled data on infants (age 1 year or younger) with congenital cardiovascular defects from three large birth defect registries in California, Sweden, and France. Altogether, 12,932 infants had one or more congenital heart defects out of 4.4 million live births and stillbirths. The registries in Sweden and France obtained data through reporting from various sources; in California, medical records were reviewed. As expected, definitions and ascertained conditions differed among each of the registries. The total rates for severe defects were similar (1.43 per 1,000), but differed for specific defects. Clear differences in epidemiological characteristics existed for specific defects; for example, severe cardiac defects sex ratios were significantly high for hypoplastic left heart syndrome, d-transposition of great vessels, double outlet right ventricle, total anoralous pulmonary venous return, tetralogy of Fallot, and significantly low for pulmonary atresia without ventricular septal defect and endocardial cushion defect. Few defects were similar for several epidemiological characteristics, but, for example, the combination of ventricular and atrial septal defects appeared equivalent with endocardial cushion defect under some circumstances, yet behaved differently with regard to associated noncardiovascular defects.

Age Factors↗
PubMed2002

Neurons with mu opioid receptors interact indirectly with enkephalin-containing neurons in the rat dentate gyrus.

In the dentate gyrus, mu opioid receptors (MORs) and their enkephalin agonists have overlapping distributions and influence excitability and plasticity. Released endogenous enkephalins can activate at least some of these MORs; however, whether these interactions involve synaptically associated profiles or more distant associations and whether some subcellular compartments (e.g., terminals or dendrites) are more likely to be targeted than others are not known. To elucidate the relationships between potential sites of enkephalin release and MORs, MOR1 and leucine-enkephalin (LE) immunoreactivities were localized in the hilus by electron microscopy, using immunoperoxidase and immunogold markers. Of the 573 MOR-immunoreactive (ir) profiles analyzed, most were axons and terminals (51 and 30%, respectively), and fewer were dendrites (12%), glia (3%), or unclassifiable (4%). Most MOR-ir profiles resembled interneuron processes, while most LE-ir terminals resembled mossy fibers. One third of MOR-ir profiles were within 3 microm and approximately half were within 4 microm of the nearest LE-ir profile. In contrast, few (3%) MOR-ir profiles contacted LE-ir profiles; only 16% of these contacts included observable synapses, and very few profiles (0.5%) colocalized MOR and LE immunoreactivity. MOR-ir axons, terminals, and dendrites were not distributed differently relative to LE-ir profiles. These results suggest that activation of hilar MORs by LE usually involves short-range volume transmission and that dendritic MORs are as likely as axonal and terminal MORs to be activated by released LE. However, the greater abundance of MOR-ir axons and terminals compared to dendrites indicates that presynaptic profiles are a more prominent target for enkephalins and exogenous MOR agonists such as morphine.

Animals↗
PubMed2001

The topography of tactile working memory.

To investigate the contribution of topographically organized brain areas to tactile working memory, we asked human subjects to compare the frequency of two vibrations presented to the same fingertip or to different fingertips. The vibrations ranged from 14 to 24 Hz and were separated by a retention interval of variable length. For intervals <1 sec, subjects were accurate when both vibrations were delivered to the same fingertip but were less accurate when the two vibrations were delivered to different fingertips. For 1 or 2 sec intervals, subjects performed equally well when comparing vibrations delivered either to the same finger or to corresponding fingers on opposite hands, but they performed poorly when the vibrations were delivered to distant fingers on either hand. These results suggest that working memory resides within a topographic framework. As a further test, we performed an experiment in which the two comparison vibrations were presented to the same fingertip but an interference vibration was presented during the retention interval. The interpolated vibration disrupted accuracy most when delivered to the same finger as the comparison vibrations and had progressively less effect when delivered to more distant fingers. We conclude that topographically organized regions of somatosensory cortex contribute to tactile working memory, possibly by holding the memory trace across the retention interval. One stimulus can be accurately compared with the memory of a previous stimulus if they engage overlapping representations, but activation of the common cortical territory by an interpolated stimulus can disrupt the memory trace.

Adult↗
PubMed2001

Object orientation agnosia: a failure to find the axis?

A dissociation between the ability to recognize misoriented objects and to determine their orientation has been reported in a small number of patients with vascular lesions. In this article, we describe a 57-year-old man with probable Alzheimer' s disease who shows the same dissociation. Neuroimaging findings indicated marked hypometabolism in the posterior cortical regions, particularly the postero-superior parietal lobes. Clinically, the patient had good object recognition accompanied by severely impaired spatial abilities. The experimental investigations comprised a variety of tasks in which he identified misoriented objects, evaluated the orientation of single objects, or discriminated the orientation of simultaneously presented items. Results revealed that his object recognition was independent of orientation and was largely mediated by salient features. With respect to orientation judgements, the patient displayed a profound inability to judge the orientation of nonupright objects, but remarkably intact (though largely implicit) knowledge of the upright orientation. Strikingly, his orientation judgements were also more accurate for upside-down objects than for other orientations (i.e., 90 degrees ). We interpret these results as evidence that judgements about object orientation are facilitated when the orientation of the principal axis of the object matches that of an internal representation. We propose that the inability to determine other orientations may be due to the failure of an "axis-finding" mechanism implemented in the posterior parietal lobes, that translates between object-centered and eye-centered coordinates appropriate for guiding visual scanning.

Agnosia↗
PubMed2001

trans-4-[(4-dimethylaminophenyl)-iminomethyl]-N-methyllpyridinium para-toluenesulfonate.

In the title compound, C15H18N3+*C7H7O3S-, the phenylene and pyridyl rings are somewhat twisted with respect to each other, forming a dihedral angle of 23.49 (6) degrees. The compound contains a dipolar chromophoric cation, but crystallizes in the centrosymmetric space group P2(1)/n and is thus not expected to display quadratic non-linear optical effects.

Journal Article↗
PubMed2001

Kappa opioid receptor density is consistent along the rostrocaudal axis of the female rat spinal cord.

Kappa opioid receptors (KORs) were immunocytochemically localized at four different levels of the spinal cord of normally-cycling female rats in estrus or diestrus. KOR labeling was primarily observed in fine processes and a few neuronal cell bodies in the superficial dorsal horn and the dorsolateral funiculus. Quantitative light microscopic densitometry of the superficial dorsal horn revealed that there were no significant differences in KOR densities among spinal segments C1--C2, T2, T13--L1, and L6--S1 in either the estrus or diestrus phases. These results suggest that the potential for KOR-mediated antinociceptive responses is consistent along the rostrocaudal axis of the female rat spinal cord.

Animals↗
PubMed2001

The topography of tactile learning in humans.

The spatial distribution of learned information within a sensory system can shed light on the brain mechanisms of sensory-perceptual learning. It has been argued that tactile memories are stored within a somatotopic framework in monkeys and rats but within a widely distributed network in humans. We have performed experiments to reexamine the spread of tactile learning across the fingertips. In all experiments, subjects were trained to use one fingertip to discriminate between two stimuli. Experiment 1 required identification of vibration frequency, experiment 2 punctate pressure, and experiment 3 surface roughness. After learning to identify the stimuli reliably, subjects were tested with the trained fingertip, its first and second neighbors on the same hand, and the three corresponding fingertips on the opposite hand. As expected, for all stimulus types, subjects showed retention of learning with the trained fingertip. However, the transfer beyond the trained fingertip varied according to the stimulus type. For vibration, learning did not transfer to other fingertips. For both pressure and roughness stimuli, there was limited transfer, dictated by topographic distance; subjects performed well with the first neighbor of the trained finger and with the finger symmetrically opposite the trained one. These results indicate that tactile learning is organized within a somatotopic framework, reconciling the findings in humans with those in other species. The differential distribution of tactile memory according to stimulus type suggests that the information is stored in stimulus-specific somatosensory cortical fields, each characterized by a unique receptive field organization, feature selectivity, and callosal connectivity.

Adult↗
PubMed2001

Contextual control over the expression of fear in rats conditioned under a benzodiazepine.

RATIONALE: Benzodiazepines disrupt fear conditioning, but this disruption is context-specific; if rats have been conditioned under a benzodiazepine, their fear is recovered if they are tested in a different context. The present experiments investigated how the conditioning context controls fear in rats conditioned under a benzodiazepine. OBJECTIVES: The experiments had three aims: (1) to replicate the finding that fear is recovered when rats are tested in a different context, (2) to test whether the conditioning context reduces fear generally or only for the specific stimulus conditioned in that context and (3) to test whether latent inhibition of the conditioning context reduces its control over fear. METHODS: Rats were injected with the benzodiazepine midazolam (1.25 mg/kg) or saline and exposed to a conditioned stimulus (CS) and shock in a distinctive chamber. Latent inhibition of the chamber was induced by extensively preexposing the rats to the chamber. The day after conditioning, fear was assessed by presenting the CS while rats were in either the conditioning chamber or a different chamber. RESULTS: The midazolam-induced reduction of fear was reversed (i.e. fear was partially recovered) if rats were tested in the different context, and was completely prevented if the conditioning context had been latently inhibited. These two effects were not additive since, when the conditioning context had been latently inhibited, rats showed less fear in the different context than in the conditioning context. CONCLUSIONS: We argue that midazolam does not disrupt conditioning, but imbues the conditioning context with control over retrieval of the CS-shock association. In this regard, the effects of midazolam closely parallel those of extinction.

Animals↗
PubMed2001

Complications in tunneled CVL versus PICC lines in very low birth weight infants.

OBJECTIVE: Comparison of complications associated with tunneled central venous lines (TCVLs) versus peripherally inserted central catheters (PICCs) in infants <1500 g. STUDY DESIGN: A retrospective cohort study at a university medical center. A total of 96 catheters were placed in 60 infants between 4/94 and 3/99. A retrospective review of these infants' medical record was done to review associated complications of catheter placement. RESULTS: Both groups had similar weights and gestational ages. The duration of catheterization was 28 days in TCVLs and 11 days in PICCs (p<0.05). Total, infectious, and mechanical complications between the two groups were similar. Survival function estimates showed no difference between the two groups up to the 15th day of catheterization. CONCLUSION: There is no difference in efficacy or associated complications between the two groups. If one could anticipate needing a catheter longer than 15 days, then a TCVL might be the better choice.

Catheterization, Central Venous↗
PubMed2001

CPT changes in 2001.

Explore the source record for details and available documents.

Abstracting and Indexing↗
PubMed2001

The heritability of attitudes: a study of twins.

The genetic basis of individual differences in attitudes was examined in a survey of 195 pairs of monozygotic twins and 141 pairs of same-sex dizygotic twins. A principal components analysis of the 30 attitude items in the survey identified 9 attitude factors, of which 6 yielded significant heritability coefficients. Nonshared environmental factors accounted for the most variance in the attitude factors. Possible mediators of attitude heritability were also assessed, including personality traits, physical characteristics, and academic achievement. Analyses showed that several of these possible mediators correlated at a genetic level with the heritable attitude factors, suggesting that the heritability of the mediator variables might account for part of the heritable components of some attitudes. There was also some evidence that highly heritable attitudes were psychologically "stronger" than less heritable attitudes.

Achievement↗
PubMed2001

Extra-abdominal pneumodissection after laparoscopic antireflux surgery.

The presence of pneumoperitoneum during laparoscopic antireflux surgery can lead to the dissection of carbon dioxide into the mediastinum, retroperitoneum, subcutaneous tissues, and neck (pneumodissection). The purpose of this study is to describe the incidence, extent, duration and pathways of pneumodissection during laparoscopic antireflux surgery. Twenty patients who underwent laparoscopic antireflux surgery from August 1998 through May 1999 were studied. Physical examination and chest radiographs were performed in the recovery room and each day postoperatively. Noncontrast computerized tomography (CT) of the neck, chest, and upper abdomen was also performed on postoperative day one. Subcutaneous emphysema and radiologic evidence of pneumodissection occurred commonly and typically resolved within 4 days postoperatively. The incidence of pneumomediastinum (85%) seen on CT scan was similar to that of pneumodissection into the neck (80%). The most common pathway of dissection of gas was through the anterior mediastinum and into the neck through the carotid space. Other findings on CT scan revealed pneumoperitoneum in 70 per cent, pneumoretroperitoneum in 10 per cent, and pneumothorax in 0 per cent. The dissection of gas into the mediastinum, neck, and subcutaneous tissues is very common after laparoscopic antireflux surgery. Subcutaneous emphysema on physical examination and radiographic pneumodissection typically resolves within 3 to 4 days. After this time one should consider the presence of any substantial amount of gas as a potential complication related to the procedure.

Carbon Dioxide↗
PubMed2001

When a hernia is not a hernia: the evaluation of inguinal hernias in the cirrhotic patient.

Herniorrhapy in patients with advanced portal hypertension and ascites should be approached with caution, and treated conservatively whenever possible. Cirrhosis increases the risk of significant perioperative complications such as infection, recurrence, and ascites leak. This paper reports two patients operated on for suspected inguinal hernias. The first patient was referred for elective repair of a presumed inguinal hernia before liver transplantation. The second patient presented with a history of an incarcerated inguinal hernia that was previously reduced in the emergency center. After examination by residents and senior faculty the patients were scheduled for elective herniorrhaphy. Intraoperatively no inguinal hernia could be identified in either patient. However, massively dilated veins (1.5-2.0 cm in diameter) were noted entering with the spermatic cord at the internal inguinal ring. In both cases the veins were clamped, transected, and suture ligated at the internal ring. Given the unusual presentation of these dilated veins in both patients we advocate the use of preoperative Doppler ultrasound in patients with cirrhosis and suspected inguinal hernias.

Aged↗
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↗