A pilot behavioural and biological surveillance survey for HIV and other bloodborne infections among Aboriginal people in Regina, Saskatchewan.

BACKGROUND: Aboriginal people in Canada are disproportionately affected by HIV and other blood-borne infections. A-Track is a national public health surveillance system designed to monitor HIV and related infections, behaviours and socio-demographic factors among Aboriginal populations in Canada. The pilot survey for the A-Track surveillance system, the first of its kind in Canada, was conducted in Regina, Saskatchewan and implemented via a community and public health partnership. OBJECTIVE: To assess the prevalence of HIV, hepatitis C, syphilis and associated risk behaviours and socio-demographic factors among Aboriginal people in Regina, Saskatchewan. This focus of the pilot survey was to provide this surveillance information for public health action and to determine whether this type of public health surveillance activity could be conducted in an urban setting across Canada. METHODS: Survey participants were self-identified Aboriginal people (First Nations, Inuit or Métis) or those who claimed Aboriginal ancestry and between the ages of 16 and 60 years. These individuals were also asked to provide a blood sample for HIV, hepatitis C and syphilis antibody testing. Descriptive analyses were performed with sex-based comparisons. RESULTS: There were 1064 people who participated in the survey. Their average age was 33 years and 51% were male. The majority of participants (93%) lived in urban Regina at the time of the survey. Just over half (53.2%) of all participants had been removed from their families during childhood; 29.9% had lived in a residential or boarding school during childhood; and 57.7% had lived at some point in a correctional facility. Among the 1,045 participants who provided a blood sample of sufficient quantity for testing, 5.2% were HIV seropositive and 55.8% of these were aware of their HIV status. The lifetime exposure to hepatitis C was 41.6%, with significantly higher proportions of males than females testing positive for hepatitis C exposure. Syphilis seroprevalence was very low (<1%). Almost three-quarters (71.5%) of participants reported being tested for HIV at least once in their lifetime and among those ever tested, 67.6% had been tested during the 12 months prior to the interview. CONCLUSION: Aboriginal people are disproportionately affected by the HIV/AIDS epidemic in Canada. The findings from the A-Track pilot survey can be used to inform and evaluate prevention and treatment services for HIV and other related infections among Aboriginal people. Lessons learned from the pilot survey could also be used to guide the possible implementation of A-Track in other urban and/or reserve locations in Canada.

Differences in the luminance of the first and second displays affects visible persistence in opposite ways.

Visible persistence was measured using a two-frame temporal integration paradigm. Most such studies match the brightness of the two frames, and find that equal increases in the brightness of the frames impairs performance on the task. This suggests that increases in frame brightness decrease the duration of visible persistence. Little is known about what happens when the frames differ in brightness. In this study, the luminance intensities of the first and second frames were set at five different intensity levels in a factorial arrangement. Increasing the intensity of the first frame improved performance, whereas increasing the intensity of the second frame impaired performance. These results suggest, contrary to the findings with brightness-matched frames, that increasing the intensity of one frame increases the duration of visible persistence of that frame. A mathematical model supports this conclusion.

Binocular brightness: a suppression-summation trade off.

In two experiments, 13 and 9 subjects estimated binocular brightness of targets of large visual extent. On each trial one eye was presented with a fairly intense luminance of 800 cd/m2, and the other eye with one of 12 luminances ranging from zero to 800 cd/m2. The first experiment, using ganzfeld stimuli (stimuli of uniform luminance that cover the entire visual field), produced a large amount of binocular brightness summation and very little Fechner's paradox, a decrease in binocular brightness that occurs when the luminances to the two eyes differ greatly. The second experiment, using a smaller target with very low spatial frequencies, produced greater Fechner's paradox than the ganzfelder, but more binocular summation and less Fechner's paradox than what is usually reported for small targets with abrupt contours. The results suggest a trade off between suppressive and summative mechanisms involving binocular cells that are spatially tuned. The trade off is controlled in the vector-sum model by the angle between vectors, which reflects the total inhibition in spatially tuned, binocular channels.

Sensory neurons of the rat sciatic nerve.

Experiments have been undertaken in this laboratory over recent years to accurately determine the numbers and sizes of somatic neurons which contribute to the normal sciatic nerve, at mid-thigh levels, of the adult, albino rat. This article is concerned with the dorsal root ganglion (DRG) neuron population of the sciatic nerve whose cell bodies were identified through retrograde labeling of cut branches of the sciatic with horseradish peroxidase (HRP) and/or its wheat germ conjugate (WGA-HRP). It is essential to understand the neuronal composition of the normal rat sciatic nerve if the consequences of aging, nerve injury, and surgical repair to improve functional regeneration are to be properly evaluated. Neuron counts were determined from camera-lucida paper drawings of all labeled profiles in DRGs L3-L6 at 100 x magnification. The profiles, obtained by labeling individual branches of the sciatic nerve (sural, lateral sural, tibial, peroneal, medial, and lateral gastrocnemius/soleus nerves) were traced from 40-microns-thick, serial, frozen sections. The sizes of the perikarya, areas and diameters, were determined by tracing the perimeters of the drawn profiles on a digitizing tablet. The tablet's output was inputted directly into a specially designed computer spreadsheet which contained a mathematical table for correcting the split-cell error inherent to the sectioning process. Afferents from any given branch of the sciatic normally occupied two to three adjacent ganglia. Sciatic DRG neurons were normally located in lumbar ganglia L3-L6. Nearly 98-99% of all sciatic DRG perikarya resided in the L4 and L5 DRGs. The L6 DRG, traditionally regarded as an important contributor to the rat sciatic, contained merely 0.4% of its afferent neurons while the L3 ganglion, frequently overlooked as a contributor, contained 1.2% of the mid-thigh sciatic afferents. The mean size of rat DRG neurons was about 29 microns (550-600 microns2). The corrected counts revealed that the normal sciatic nerve (at mid-thigh levels), in rats between 2 and 12 months of age, contained a mean, total DRG neuron population of about 10,500 neurons. This is probably an underestimate by 3-5% of the true number due to occasional unreliable labeling of some of the small DRG neurons. It is estimated that the normal, mean number of sciatic DRG neurons of young to middle-aged rats lies somewhere between 10,500 and 11,000 +/- 2000. The data suggest that nearly 20% of all DRG neurons in the sciatic nerve supply muscle afferents. The vast majority of the remaining neurons are involved with innervation of the skin.(ABSTRACT TRUNCATED AT 400 WORDS)

Prostatic epithelial cells in culture: phosphorylation of protein tyrosyl residues and tyrosine protein kinase activity.

The ability of dividing canine prostatic epithelial cells in primary monolayers to phosphorylate protein tyrosyl residues was evaluated by metabolic studies performed through incorporation of [32P]-phosphate into alkali-resistant phosphoproteins and by the assay of their tyrosine protein kinase activity. The presence of sodium orthovanadate during cell incubation with [32P]-phosphate greatly enhanced the relative labelling intensity of a 44 kDa alkali-resistant phosphoprotein and the total cellular content of phosphotyrosine in proteins; in this respect, growth factors such as epidermal growth factor, insulin, and insulin-like growth factor I, and the steroids dihydrotestosterone and estradiol were inactive. When the cells were solubilized, sodium orthovanadate stimulated their tyrosine protein kinase activity and inhibited their phosphotyrosine phosphatase activity. To characterize the tyrosine protein kinase of these cultured cells, conditions for optimal activity were established using the substrate poly [Glu80Na, Tyr20]. The subcellular localization of the enzyme was determined upon cell fractionation: 88% of the kinase activity was associated with the particulate fraction and 30% of this activity was partially solubilized with 0.5% Triton X-100; this solubilization was improved to 83% in the presence of 0.25 M KCI. The enzyme directly solubilized from prostatic cells with Triton X-100 (38% of activity) mainly catalyzed the alkali-resistant phosphorylation of pp63, pp59, and pp44, which contained phosphotyrosine. These proteins were also phosphorylated by the major peak of kinase activity which was eluted at an apparent molecular weight of 300-350 kDa upon gel filtration.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of protein-tyrosine kinase activity in the canine prostate.

Following the measurement of the phosphorylation of the substrate poly(Glu80Na,Tyr20) and the analysis of the alkali-resistant phosphorylation of endogenous proteins, the protein-tyrosine kinase of the canine prostate was partially characterized with regard to its subcellular localization, as well as certain kinetic and molecular properties. This kinase was mainly found in the cytosolic fraction (75%); however, its specific activity was similar to that of the residual enzyme present in the particulate fraction. Conditions for optimal activity of both fractions were determined. Under these conditions, several endogenous phosphoproteins (44-63 kilodaltons upon electrophoresis) were alkali resistant and phosphotyrosine was present in all of the major ones (pp63, pp57, pp52, and pp44). The particulate protein-tyrosine kinase activity was partially solubilized (58%) with 0.5% Triton X-100; this percentage was increased to 85% in the presence of 0.25 M KCl. Upon gel filtration, both cytosolic and particulate kinases showed an apparent molecular mass of 44 kilodaltons; these enzymes also phosphorylated similar major alkali-resistant phosphoproteins. The soluble protein-tyrosine kinase, with a sedimentation coefficient of 4.0S and an isoelectric point of 5.5, could be separated from arginine esterase and prostatic acid phosphatase.

Enhancement of the detection of alkali-resistant phosphoproteins in polyacrylamide gels.

Following their separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, labeled proteins obtained from cultured canine prostatic epithelial cells incubated with [35S]-methionine and [32P]phosphate were subjected to alkali treatment, a method that is currently used to detect phosphotyrosine-containing proteins. Significant amounts of 35S-labeled material were lost during the alkali treatment. The crosslinking of proteins within the gels by glutaraldehyde treatment eliminated protein losses and did not alter the efficiency of phosphoester bond hydrolysis by alkali treatment. Consequently, the time required to detect alkali-resistant phosphoproteins by autoradiography was greatly reduced. Prostatic phosphoproteins were also shown to contain phosphotyrosine, indicating the presence of tyrosine protein kinase activity in these proliferating epithelial cells.

On and off systems in human vision.

Three experiments examined the interaction of On and Off responses that were produced by sudden increments and decrements in luminance. All three experiments utilized a masking technique that required observers to detect a signal in a masking field. The mask was produced by brightening or dimming a field of dots, and the signal consisted of the addition or subtraction of a dot. Experiment 1 showed that detection of the signal-dot was more difficult when the luminance of the signal and the mask changed in the same direction (e.g. a new dot added to the field of dots that were being brightened) than when luminance changed in different directions. When the amplitude of signal and mask was varied parametrically (Experiments 2 and 3), accuracy increased with the ratio of amplitudes of signal and mask. But at any given ratio, the signal was more difficult to detect when signal and mask were of the same sign. The greater difficulty encountered in detecting a signal in the context of a "like" mask is ascribed to greater interference between signal and mask when they share the channel.

Models for sensation and perception: a selective history.

This paper is a historical survey, for nonspecialists, of models used to account for sensation and perception. Emphasis is placed on several crucial ideas that have given rise to major changes in explanatory models: namely, geometrical optics, receptive fields and systems or computational approaches. The nature of sensory coding and neural representation is briefly considered against this background.

Orienting response and detection of thalamic stimulation: mechanism of perceptual learning in the cat.

Naive cats cannot use thalamic stimulation as a signal to perform a behavioral response when stimulus intensities are too weak to evoke orienting behavior. Responses are quickly learned at higher intensities of stimulation, and with continued training, the cats become able to response to the weaker, previously ineffective stimulus. This increase in sensitivity is not due to changes in tonic arousal and appears to be relatively specific to the stimulated nucleus. The procedures may be useful in exploring the neural mechanisms of perceptual learning.

Equating visibility of brief decrements: unconfounding duration and luminance.

A common procedure in visual psychophysics involves equating the visual effectiveness of brief luminous displays. It may be equally important to equate the effectiveness of brief interruptions, as when two displays are presented sequentially, separated by a variable interstimulus interval (ISI). For example, in a procedure devised by Phillips and Singer [Expl. Brain Res. 19, 493-506 (1974)], the first display consisted of a random pattern of dots and the second display consisted of the same pattern, but with one added dot. Detectability of the added dot was presumed to be determined by interactions of transient neural events produced at the beginning and end of the ISI. Lengthening the ISI was believed to weaken progressively the magnitude of the neural interactions, resulting in poorer performance. But lengthening the ISI also increased its visual effectiveness (darkness). Using ISIs equated in visual effectiveness for durations from 10 to 320 msec, we found that the visual effectiveness of the interval, not its duration, was the prime determinant of performance. This finding requires a reinterpretation of the neural mechanisms being studied in the Phillips and Singer task.

Specificity of submaxillary gland sialyltransferases.

A method has been developed to determine the activities of specific sialyltransferases by analysis of the products of the reaction. This method, which utilizes high performance liquid chromatography, distinguishes addition of sialic acid to the N-acetylgalactosamine vs. galactose residues of the mucin disaccharide Gal beta(1 leads to 3)GalNac, and can be used to distinguish formation of the 3'- and 6'-isomers of sialyllactose. For the bovine, ovine, and porcine submaxillary extracts, more than 95% of the activity with asialo ovine submaxillary mucin is due to formation of NeuAc alpha(2 leads to 6)GalNAc. With lactose as the acceptor, more than 95% of the alpha(2 leads to 3) isomer is produced. Activity with asialofetuin is due solely to the O-linked chain, with relative activity toward the galactose vs. GalNAc residues of 0.32, 1.5, and 0.10 for bovine, ovine, and porcine, respectively. The rat submaxillary gland extract showed equal formation of 3'- and 6'-sialyllactose, and very low activity with asialo ovine submaxillary mucin. However, at least 40% of the activity toward the Gal beta(1 leads to 3)GalNAc disaccharide of asialofetuin was directed toward the GalNAc residue. The relative preference of the N-acetylgalactosaminide alpha(2 leads to 6) sialyltransferase for a monosaccharide vs. a substituted GalNAc may play a role in regulation of chain length during mucin synthesis.

Urinary alpha-L-fucosidase in cystic fibrosis.

The binding of the urinary lysosomal enzyme alpha-L-fucosidase to free- and Sepharose 4B-bound concanavalin A has been compared in cystic fibrosis (CF) patients and normal controls. The concentration of methyl-alpha-D-mannoside necessary to prevent 50% of total alpha-L-fucosidase activity to bind to free and bound concanavalin A (Ki, 50%) was similar for CF (0.68 +/- 0.20 and 1.3 +/- 0.3 mmol/l, respectively) and normal controls (0.53 +/- 0.18 and 1.9 +/- 0.5 mmol/l, respectively). The CF and normal urinary alpha-L-fucosidase also showed similar pH optima (4.8), Km, app (0.071 and 0.074 mmol/l, respectively) and thermodenaturation curves at 44 degrees C (t1/2 = 108 min). We report that the kinetic and the concanavalin A-binding affinity of alpha-L-fucosidase are similar from urine of cystic fibrosis patients and controls.

Temporal integration following intensification of long-lasting visual displays.

Duration of visible persistence is known to be inversely related to the duration of the inducing stimulus, within a critical interval estimated at between 100 and 150 msec. Stimuli longer than the critical interval yield little or no persistence. Six experiments investigated whether a brief period of intensification at the end of a stimulus longer than the critical interval could restore visible persistence. In the first experiment, a punctate stimulus ceased to give rise to visible persistence at exposure durations longer than the critical interval. The second experiment showed that persistence could be restored to a long display by briefly intensifying the component dots just before the end of the display. The remaining four experiments explored the limits and the distinguishing characteristics of this effect. Two alternative explanations of the results are described and evaluated.

Behavioral detection of subcortical stimuli: comparison of somatosensory and "motor" circuits.

Cats were trained to press a lever for food reinforcement in response to stimulation of the ventral lateral (VL) nucleus of the thalamus and the deep cerebellar nuclei. By scaling stimulus intensities relative to the appearance of a minimal amplitude evoked response in pericruciate cortex, it was possible to measure behavioral detection thresholds and correlate behavior with electrocortical activity. With stimulus rates of 25 Hz or greater, VL was the least effective stimulus site for producing detection. At stimulus rates less than 25 Hz, stimulation of the lateral or interpositus nuclei was even less effective in eliciting behavior, but at rates of 25 Hz or more, detection thresholds decreased below those for VL stimulation; cerebellar stimulation produced detection as readily as had stimulation of the ventrobasal complex in other experiments. These findings suggest that the cerebellum may modulate sensory experiences and that some portions of cerebral cortex, the pericruciate and suprasylvian regions, do not appear to be directly involved in mediating sensory detection. It is postulated that the neural detection circuits are more likely to be found in subcortical than in cerebrocortical structures.

Lesions of the dorsal column nuclei or medial lemniscus of the cat: effect on motor performance.

Motor performance in cats was evaluated by means of a beam-walking task after bilateral lesions were made in dorsal column nuclei (DCN) or medial lemniscus (ML) near its entrance to thalamus. Coordinated motor activity was not significantly impaired by ML lesions or by DCN lesions limited to the main nuclei, but was impaired by larger lesions to DCN that also involved the external cuneate nuclei.

Detection thresholds to stimulation of ventrobasal complex in cats.

Cats were trained to indicate, by bar pressing for food rewards, their detection of stimulation of the ventrobasal (VB) complex delivered through implanted bipolar electrodes. By varying stimulus intensity it was possible to determine thresholds for detection. Scaling stimulus intensity relative to the appearance of a minimal evoked potential allowed comparisons between animals and also comparisons with results obtained by stimulation of peripheral nerve. Animals could detect VB stimulation, but only at stimulus intensities consistently stronger than those required for minimal appearance of an evoked response in ipsilateral primary somatosensory cortex. Results of VB activation differed from cutaneous nerve effects in that VB detection thresholds were markedly influenced by stimulus frequency. They were lowest at frequencies above 30 Hz and increased greatly at lower frequencies. Discomfort or pain did not seem to result even from relatively high stimulus intensities. The results compare well with observations obtained from stimulation of VB in humans. The appearance of an evoked cortical response is not necessarily correlated with behavior. Under appropriate conditions, behavior can be elicited predictably with minimal electrocortical activity; under other conditions detection may be absent even when large numbers of cortical neurons are activated. We suggest that regions of the cerebral cortex receiving thalamocortical projections from VB may not be essential in the detection process.