Laminar and columnar patterns of geniculocortical projections in the cat: relationship to cytochrome oxidase

We examined the laminar and columnar arrangement of projections from different layers of the lateral geniculate nucleus (LGN) to the visual cortex in the cat. In light of recent reports that cytochrome oxidase blobs (which in primates receive specific geniculate inputs) are also found in the visual cortex of cats, the relationship between cytochrome oxidase staining and geniculate inputs in this species was studied. Injections of wheat germ agglutinin-conjugated horseradish peroxidase were made into the anterior "genu" of the LGN, where isoelevation contours of the geniculate layers are distorted due to the curvature of the nucleus. Consequently, anterograde labeling from the various LGN layers was topographically separated across the surface of the cortex, and labeling in a particular isoelevation representation of the cortex could be associated with a specific layer of the LGN. Labeling from the A layers, which contain X and Y cells, was coextensive with layers 4 and 6 in both area 17 and area 18, as previously reported. Labeling from the C layers, which contain Y and W cells, occupied a zone extending from the 4a/4b border to part way into layer 3 in area 17. The labeling extended throughout layer 4 in area 18. There was also labeling in layer 5a and layer 1 in both area 17 and area 18. Except in layer 1, labeling from the C layers was patchy. In the tangential plane, adjacent sections stained for cytochrome oxidase showed that the patches of labeling from the C laminae aligned with the cytochrome oxidase blobs. The cytochrome blobs were visible in layers 3 and 4a, but not in layer 4b in both areas 17 and 18. These results suggest that W cells project specifically to the layer 3 portion of the blobs, while Y cells, at least those of the C layers, project specifically to the layer 4a portion of the blobs in area 17. The heavy synaptic drive of the Y cells is probably the cause of the elevated metabolism, and thus, higher cytochrome oxidase activity, of the blobs.     

Dexamethasone induces an increase in intracellular and membrane-associated lipocortin-1 (annexin-1) in rat astrocyte primary cultures

1. The antiinflammatory actions of glucocorticoid steroids are thought to occur through induction of the protein lipocortin-1 (LC-1; annexin-1). The purpose of the current study was to investigate whether astrocytic LC-1 content was increased in the presence of a synthetic glucocorticoid, dexamethasone. 2. Steroid-induced changes in cellular levels of LC-1 in astrocytes were determined by electrotransfer and immunoblotting techniques. Separate cell fractions were investigated to study the influence of dexamethasone on astroglial LC-1 content. The effect of culture state on LC-1 expression was also examined. 3. Intracellular LC-1 content was found to decrease after initiation of culture, with a substantial rise in both cell proliferation and LC-1 expression occurring after the replenishment of medium containing steroid-free serum. A further increase in intracellular LC-1 occurred upon incubation with dexamethasone. The glucocorticoid-induced change in intracellular LC-1 was a time-dependent event and coincided with an increase in membrane-associated LC-1. 4. The findings in this study indicate that astrocytic LC-1 content is influenced by cell culture conditions and, in the presence of glucocorticoid steroids, the cellular localization of LC-1 is altered. This may indicate that LC-1 has functions at more than one cellular locality.     

Efficacy of silicone punctal plugs as adjuncts to topical pharmacotherapy of glaucoma--a pilot study. Punctal Plugs in Glaucoma Study Group

BACKGROUND: The concept of enhancing the ocular hypotensive effects of topical antiglaucoma medications by impeding lacrimal drainage of medication has been insufficiently studied. This investigation sought to evaluate the effect of bilateral inferior punctal occlusion using silicone punctal plugs on the ocular hypotensive effect of topically applied timolol. METHODS: A randomized, double-masked, cross-over clinical trial was conducted, comparing the ocular hypotensive effect of timolol maleate 0.25 percent, both with and without occlusion of the inferior punctum with the Freeman silicone punctal plug. Following a 2-week washout of topical medication, 17 subjects with early primary open-angle glaucoma or ocular hypertension received one drop of timolol 0.25 percent in each eye with or without punctal plugs in place. Blood pressure, resting pulse rate, and intraocular pressure were measured both before timolol instillation and at intervals of 1, 2, 4, 8, and 12 hours following drop instillation. Following a 2-week washout period, the subjects were evaluated with the alternative treatment. RESULTS: There was no statistically significant difference (p = 0.648) in IOP levels between treatment groups. CONCLUSIONS: This pilot suggests that need for a longer-term study with larger numbers of subjects to evaluate the potential role of silicone punctal plugs to enhance the ocular bioavailability of topically applied antiglaucoma medications.     

Assessment of baroreceptor-cardiac reflex sensitivity using time domain analysis in patients with IDDM and the relation to left ventricular mass index

Autonomic dysfunction in insulin-dependent diabetic (IDDM) patients has been associated with abnormalities of left ventricular function and an increased risk of sudden death. A group of 30 patients with IDDM and 30 age, sex and blood pressure matched control subjects underwent traditional tests of autonomic function. In addition, baroreceptor-cardiac reflex sensitivity (BRS) was assessed using time domain (sequence) analysis of systolic blood pressure and pulse interval data recorded non-invasively using the Finapres beat-to-beat blood pressure recording system. 'Up BRS' sequences-increases in systolic blood pressure associated with lengthening of R-R interval, and 'down BRS' sequences-decreases in systolic blood pressure associated with shortening of R-R interval were identified and BRS calculated from the regression of systolic blood pressure on R-R interval for all sequences. We also assessed heart rate variability using power spectral analysis and, after expressing components of the spectrum in normalised units, assessed sympathovagal balance from the ratio of low to high frequency powers. IDDM subjects underwent 2-D echocardiography to assess left ventricular mass index. Standard tests of autonomic function revealed no differences between IDDM patients and control subjects, but dramatic reductions in baroreceptor-cardiac reflex sensitivity were detected in IDDM patients. 'Up BRS' when supine was 11.2 +/- 1.5 ms/mmHg (mean +/- SEM) compared with 20.4 +/- 1.95 in control subjects (p < 0.003) and when standing was 4.1 +/- 1.9 vs 7.6 +/- 2.7 ms/mmHg (p < 0.001). Down BRS when supine was 11.5 +/- 1.2 vs 22 +/- 2.6 (p < 0.001) and standing was 4.4 +/- 1.9 vs 7.3 +/- 2.5 ms/mmHg (p < 0.003). There were significant relations between impairment of the baroreflex and duration of diabetes (p < 0.001) and poor glycaemic control (p < 0.001). From a fast Fourier transformation of supine heart rate data and using a band width of 0.05-0.15 Hz as low-frequency and 0.2-0.35 Hz as high frequency total spectral power of R-R interval variability was significantly reduced in the IDDM group for both low-frequency (473 +/- 62.8 vs 746.6 +/- 77.6 ms2 p = 0.002) and high frequency bands 125.2 +/- 12.9 vs 459.3 +/- 89.8 ms2 p < 0.0001. When the absolute powers were expressed in normalised units the ratio of low frequency to high frequency power (a measure of sympathovagal balance) was significantly increased in the IDDM group (2.9 +/- 0.53 vs 4.6 +/- 0.55, p < 0.002 supine: 3.8 +/- 0.49 vs 6.6 +/- 0.55, p < 0.001 standing). Thus, time domain analysis of baroreceptor-cardiac reflex sensitivity detects autonomic dysfunction more frequently in IDDM patients than conventional tests. Impaired BRS is associated with an increased left ventricular mass index and this abnormality may have a role in the increased incidence of sudden death seen in young IDDM patients.     

Mechanical response properties of nociceptors innervating feline hairy skin

1. The responses of feline cutaneous nociceptors were examined in vivo by systematically manipulating the intensive and spatial dimensions of mechanical stimulation. A computer-controlled motor was used to apply prescribed forces (5-90 g) to a nociceptor's receptive field, with flat-tipped, cylindrical probes of various sizes (contact areas: 0.1-5.0 mm2). The stimulating device and protocols were similar to those previously used to evaluate human perception, thus allowing for comparisons of the two data sets. 2. With a ramp-and-hold stimulus of controlled force, most nociceptors showed a slowly adapting (SA) response throughout the stimulus. In this way, nociceptors resembled low-threshold SA mechanoreceptors. However, in contrast to SA mechanoreceptors, nociceptors failed to exhibit an onset burst of activity associated with the stimulus ramp. Nineteen percent (6 of 31) of the nociceptors often showed the opposite trend during the stimulus, e.g., a gradually increasing firing rate. Most of these nociceptors (5 of 6) had particularly high mechanical thresholds. 3. With 30 stimuli repeated at short intervals (6-8 s), response rates tended to decrease across trials. This phenomenon was most evident with more intense stimuli. When two series of stimuli were separated by 4-5 min, there was no apparent trend of reduced responsiveness between series. 4. Overall, nociceptors responded in an orderly way to variations in force and probe size. For a given probe size, larger forces produced greater responses; for a given force, smaller probes produced greater responses. The relationship between probe size and force was best described as an even tradeoff between force and a linear dimension of the probe (i.e., probe perimeter), rather than the area of the probe. Thus a given pressure (force/area) did not evoke the same response from nociceptors as probe size was varied. 5. There were two significant differences in the mechanical responsiveness between A fiber and C fiber nociceptors. First, for a given set of stimuli, A fiber nociceptors exhibited a greater response rate than the C fiber nociceptors. Second, the A fiber nociceptors exhibited a greater differential response related to probe size than the C fiber nociceptors. On the basis of these two features, the A fiber nociceptors' response profiles showed a closer parallel with previously reported human pain thresholds than the C fiber nociceptors did. 6. When the nociceptors were subdivided as to their mechanical threshold, those with lower thresholds [mechanically sensitive afferents (MSAs)] showed a response saturation with the more intense stimuli. On average, the stimulus levels at which saturation occurred were close to human pain threshold. Those nociceptors with higher thresholds [mechanically insensitive afferents (MIAs)] did not show such saturation. Thus only the MIAs appeared to have the capacity to unambiguously encode mechanical stimulus intensities above pain threshold. The MSAs, on the other hand, exhibited their greatest dynamic response range near the threshold for nonpainful sharpness. Thus the group of afferents commonly defined as nociceptors exhibit a heterogeneity of mechanical response properties, which may serve functionally different roles for perception.     

Model of a miniature pig catheterized for pharmacokinetic and pharmacodynamic studies of anti-infective agents

The purpose of this study was to examine the role of sleep problems in the etiology of nursing caries. Two-hundred mothers of children (104 with nursing caries and 96 caries free) from ages 2 to 4.5 years were surveyed to determine whether difficulty with child sleep and ensuing sleep-associated feeding might be related to the presence of nursing caries. Differences were noted between these two groups regarding: average number of nights the child slept through the night (P < 0.001); total hours of sleep per night (P < 0.05); frequency of night waking episodes (P < 0.01); feeding on demand upon waking (P < 0.01); using a bottle to assist with falling asleep at night (P < 0.001); and feeding in association with nap time (P < 0.001). Differences also were noted in regard to average age of weaning (P < 0.001). Our findings suggest that sleep problems among young children are a behavioral risk factor for night-time bottle use and early childhood caries.     

Responses of dairy cows supplemented with somatotropin during weeks 5 through 43 of lactation

Beginning at wk 5 of lactation, 136 cows (34 per treatment) were supplemented daily for 38 wk with 0, 10.3, 20.6, or 41.2 mg of recombinantly derived bST monomer. Cows were obtained from University of Kentucky, University of Minnesota, University of Pennsylvania, and The Ohio State University. Nine cows (4 at 0 mg/d, 1 at 10.3 mg/d, 1 at 20.6 mg/d, and 3 at 41.2 mg/d) did not complete the experiment because of health problems. Data from these cows were included in the reproduction and health databases but not in the production database. Cows supplemented with bST produced more milk, consumed more feed, had lower rates of BW gain, and had improved efficiencies of milk production (conversion of feed and NEL to milk). Additional increases in productivity were modest at 20.6 and 41.2 mg/d versus productivity at 10.3 mg/d of bST. Concentrations of fat, protein, and TS in milk were unaffected. At 10.3 mg/d, bST did not adversely affect reproduction or health.