Presynchronization with Double-Ovsynch improves fertility at first postpartum artificial insemination in lactating dairy cows.

The objective of this study was to compare circulating progesterone (P4) profiles and pregnancies per AI (P/AI) in lactating dairy cows bred by timed artificial insemination (TAI) following Ovsynch-56 after 2 different presynchronization protocols: Double-Ovsynch (DO) or Presynch-Ovsynch (PS). Our main hypothesis was that DO would increase fertility in primiparous cows, but not in multiparous cows. Within each herd (n=3), lactating dairy cows (n=1,687; 778 primiparous, 909 multiparous) were randomly assigned to DO [n=837; GnRH-7d-PGF(2α)-3d-GnRH-7d-Ovsynch-56 (GnRH-7d-PGF(2α)-56h-GnRH-16hTAI)] or PS (n=850; PGF(2α)-14d-PGF(2α)-12d-Ovsynch-56). In 1 herd, concentrations of P4 were determined at the first GnRH (GnRH1) of Ovsynch-56 and at d 11 after TAI (n=739). In all herds, pregnancy was diagnosed by palpation per rectum at 39 d. In 1 herd, the incidence of late embryo loss was determined at 74d, and data were available on P/AI at the subsequent second service. Presynchronization with DO reduced the percentage of animals with low P4 concentrations (<0.50 ng/mL) at GnRH1 of Ovsynch-56 (5.4 vs. 25.3%, DO vs. PS). A lesser percentage of both primiparous and multiparous cows treated with DO had low P4 concentrations at GnRH1 of Ovsynch-56 (3.3 vs. 19.7%, DO vs. PS primiparous; and 8.8 vs. 31.9%, DO vs. PS multiparous). Presynchronization with DO improved P/AI at the first postpartum service (46.3 vs. 38.2%, DO vs. PS). Statistically, a fertility improvement could be detected for primiparous cows treated with DO (52.5 vs. 42.3%, DO vs. PS, primiparous), but only a tendency could be detected in multiparous cows (40.3 vs. 34.3%, DO vs. PS, multiparous), consistent with our original hypothesis. Presynchronization treatment had no effect on the incidence of late embryo loss after first service (8.5 vs. 5.5%, DO vs. PS). A lower body condition score increased the percentage of cows with low P4 at GnRH1 of Ovsynch-56 and reduced fertility to the TAI. In addition, P4 concentration at d 11 after TAI was reduced by DO. The method of presynchronization at first service had no effect on P/AI at the subsequent second service (34.7 vs. 36.5%, DO vs. PS). Thus, presynchronization with DO induced cyclicity in most anovular cows and improved fertility compared with PS, suggesting that DO could be a useful reproductive management protocol for synchronizing first service in commercial dairy herds.

The Relationship Between Aphis glycines and Soybean mosaic virus Incidence in Different Pest Management Systems.

The soybean aphid, Aphis glycines, causes yield loss and transmits viruses such as Soybean mosaic virus (SMV) in soybean (Glycine max). Field experiments were designed to monitor the landing rate of A. glycines and transmission of SMV to soybean grown in six crop management environments. Management systems evaluated were the application of postemergence insecticide or no insecticide, and within each insecticide treatment no herbicide, glyphosate, or imazamox application. In 2001, early-season incidence of SMV was 2%, which increased to 80% within 18 days after the beginning of the A. glycines flight. In 2002, the incidence of SMV was 1% prior to the arrival of A. glycines, and increased to 44% within 21 days. The landing rate of A. glycines was fivefold higher in 2001 than in 2002. The incidence of SMV was lower in insecticide-treated plots in 2002, but no effect of insecticide was seen in 2001. Imazamox slowed the progression of SMV incidence, but the final incidence of SMV-infected plants was the same. Glyphosate had no consistent effect on SMV incidence. Yield was higher in the insecticide-treated plots in 2002, but not 2001. Insecticide and herbicide application had no substantial effects on seed quality.

Seasonal Progression and Agronomic Impact of Tobacco streak virus on Soybean in Wisconsin.

Pod necrosis and dieback of terminal portions of stems, commonly called bud blight, are observed in soybean fields and associated with Tobacco streak virus (TSV), an understudied virus of soybean. Furthermore, many TSV-infected plants are asymptomatic. The objectives of this study were to characterize the distribution and seasonal progress of TSV-infected plants in both natural and controlled epidemics, and the agronomic impact of TSV on soybean in plots with controlled introduction of inoculum. Incidence of TSV-positive samples ranged from 17 to 56% in a general survey. In the presence of natural sources of inoculum, the incidence of TSV-infected plants ranged from 10 to 95% depending on cultivar and location, and peaked at growth stage R2, but detection dropped dramatically at R5. During 2001, significant yield loss and incidence of mottled seed were associated with TSV, but results were confounded by a high incidence of SMV. In 2002, SMV was controlled by cultivar selection, and a 25% reduction in grain yield was attributable to TSV. The incidence of mottled seed and green stem syndrome were low in the presence of TSV. Reductions in plant density and final plant height contributed to reduced yields. However, no significant differences were found in seed number per plant and 100-seed weight. Data indicate that plant mortality was the main mechanism by which TSV caused yield loss in induced epidemics.

Impact of Herbicides on Heterodera glycines Susceptible and Resistant Soybean Cultivars.

Several abiotic and biotic stresses can affect soybean in a growing season. Heterodera glycines, soybean cyst nematode, reduces yield of soybean more than any other pathogen in the United States. Field and greenhouse studies were conducted to determine whether preemergence and postemergence herbicides modified the reproduction of H. glycines, and to determine the effects of possible interactive stresses caused by herbicides and H. glycines on soybean growth and yield. Heterodera glycines reproduction factor (Rf) generally was less on resistant than susceptible cultivars, resulting in a yield advantage for resistant cultivars. The yield advantage of resistant cultivars was due to more pods per plant on resistant than susceptible cultivars. Pendimethalin reduced H. glycines Rf on the susceptible cultivars in 1998 at Champaign, Illinois, and in greenhouse studies reduced dry root weight of H. glycines-resistant and susceptible cultivars, therefore reducing Rf on the susceptible cultivars. The interactive stresses from acifluorfen or imazethapyr and H. glycines reduced the dry shoot weight of the resistant cultivar Jack in a greenhouse study. Herbicides did not affect resistant cultivars' ability to suppress H. glycines Rf; therefore, growers planting resistant cultivars should make herbicide decisions based on weeds present and cultivar tolerance to the herbicide.

Efficacy of Fungicides on Sclerotinia sclerotiorum and Their Potential for Control of Sclerotinia Stem Rot on Soybean.

Sclerotinia stem rot of soybean, caused by Sclerotinia sclerotiorum, is a major disease in the north central region of the United States. One approach to managing Sclerotinia stem rot on soybean is the use of fungicides. S. sclerotiorum was assayed for sensitivity to benomyl, tebuconazole, thiophanate methyl, and vinclozolin in pure cultures on agar medium, inoculated soybean seedlings, detached inoculated leaves, and in experimental field plots. To evaluate the inhibitory effect of four fungicides on growth of S. sclerotiorum in vitro, potato dextrose agar (PDA) was amended with the fungicides at six concentrations. Based on measurements of fungal radial growth, vinclozolin was the most effective in inhibiting S. sclerotiorum mycelial growth at 1.0 µg a.i./ml of PDA. Ranges of reduction of radial growth of 91 isolates of S. sclerotiorum on PDA amended with thiophanate methyl and vinclozolin were 18 to 93% and 93 to 99%, respectively, when compared with the nonamended agar control. Benomyl, thiophanate methyl, and vinclozolin applied to greenhouse-grown seedlings prevented S. sclerotiorum from expressing symptoms or signs on leaf tissue. Detached leaves sprayed with thiophanate methyl and then inoculated with mycelial plugs of S. sclerotiorum did not express symptoms or signs. Of 13 different environments in Illinois, Indiana, Ohio, and Wisconsin from 1995 through 2000, six had low Sclerotinia stem rot incidence (<1%), three environments had low to moderate Sclerotinia stem rot incidence (5 to 25%), and four environments had high Sclerotinia stem rot incidence (>25%). When disease incidence was high, no consistent control of Sclerotinia stem rot was observed with benomyl or thiophanate methyl using different application systems. However, under low disease incidence, spray systems that were able to penetrate the canopy reduced the incidence of Sclerotinia stem rot an average of 50%.

Striate cortex increases contrast gain of macaque LGN neurons.

Recurrent projections comprise a universal feature of cerebral organization. Here, we show that the corticofugal projections from the striate cortex (VI) to the lateral geniculate nucleus (LGN) robustly and multiplicatively enhance the responses of parvocellular neurons, stimulated by gratings restricted to the classical receptive field and modulated in luminance, by over two-fold in a contrast-independent manner at all but the lowest contrasts. In the equiluminant plane, wherein stimuli are modulated in chromaticity with luminance held constant, such enhancement is strongly contrast dependent. These projections also robustly enhance the responses of magnocellular neurons but contrast independently only at high contrasts. Thus, these results have broad functional significance at both network and neuronal levels by providing the experimental basis and quantitative constraints for a wide range of models on recurrent projections and the control of contrast gain.

Comparison of two estrus synchronization programs in a large, confinement-housed dairy herd.

OBJECTIVE: To compare pregnancy rates, seasonal effects, and economic benefits of 2 estrus synchronization programs for a confinement-housed dairy herd. DESIGN: Prospective cohort study. ANIMALS: 200 lactating Holstein cows. PROCEDURE: Cows eligible for breeding were palpated per rectum and randomly assigned to 2 treatment groups during 4 seasonal periods. Cows in one group (Ovsynch) received injections of gonadotropin releasing hormone (GnRH) on day 0, prostaglandin F2 alpha on day 7, and a second injection of GnRH on day 8. Cows in the other group (PP) that had a palpable corpus luteum were given prostaglandin F2 alpha. Estrus detection was not performed on the Ovsynch cows, which were artificially inseminated at a predetermined time after the second GnRH injection. Cows in the PP group were observed for signs of estrus, and only those that were detected in estrus were inseminated. RESULTS: Pregnancy rates and insemination rates were significantly improved for cows in the Ovsynch group, compared with cows in the PP group. CLINICAL IMPLICATIONS: The Ovsynch program was an economically advantageous method for controlling reproduction that resulted in pregnancies without the need for estrus detection.

Comparison of topical application of three products for treatment of papillomatous digital dermatitis in dairy cattle.

OBJECTIVE: To test the effectiveness of 3 topical sprays for treatment of papillomatous digital dermatitis (PDD) in dairy cattle. DESIGN: Prospective field trial. ANIMALS: 48 lactating cows with PDD randomly assigned to 4 groups of 12 cows each. PROCEDURE: For 3 weeks, cows in each group were treated topically with oxytetracycline solution (100 mg/ ml), acidified ionized copper solution, acidified sodium chlorite solution, or a placebo (tap water). Cows were milked 3 times daily, and at each milking, lesions were washed with a pressure hose and treatment solutions were sprayed on the lesions. Degree of lameness was graded before and after 3 weeks of treatment. RESULTS: Mean lameness score decreased (ie, cows were less lame) for all 3 treatment groups, but increased for the control group. CLINICAL IMPLICATIONS: Daily application of topical solutions was effective in decreasing degree of lameness associated with PDD in cattle tested.

Space-time spectra of complex cell filters in the macaque monkey: a comparison of results obtained with pseudowhite noise and grating stimuli.

White noise stimuli were used to estimate second-order kernels for complex cells in cortical area V1 of the macaque monkey, and drifting grating stimuli were presented to the sample of neurons to obtain orientation and spatial-frequency tuning curves. Using these data, we quantified how well second-order kernels predict the normalized tuning of the average response of complex cells to drifting gratings. The estimated second-order kernel of each complex cell was transformed into an interaction function defined over all spatial and temporal lags without regard to absolute position or delay. The Fourier transform of each interaction function was then computed to obtain an interaction spectrum. For a cell that is well modeled by a second-order system, the cell's interaction spectrum is proportional to the tuning of its average spike rate to drifting gratings. This result was used to obtain spatial-frequency and orientation tuning predictions for each cell based on its second-order kernel. From the spatial-frequency and orientation tuning curves, we computed peaks and bandwidths, and an index for directional selectivity. We found that the predictions derived from second-order kernels provide an accurate description of the change in the average spike rate of complex cells to single drifting sine-wave gratings. These findings are consistent with a model for complex cells that has a quadratic spectral energy operator at its core but are inconsistent with a spectral amplitude model.

Cross-correlation analyses of nonlinear systems with spatiotemporal inputs.

Methods are presented for analyzing the low-order stimulus-response cross-correlation functions (or kernels) of visual neurons studied with spatiotemporal white noise. In particular, formulas are derived that relate the low-order kernels of a cell to its responses to single-drifting, double-drifting, and counterphase gratings. The harmonic response terms contributed by the low-order kernels include a mean response term, first- and second-harmonic terms, and sum- and difference-harmonic terms. Using the formulas in this paper, one can obtain kernel-based predictions for the spatiotemporal-frequency tuning of each harmonic. These kernel-based predictions can then be compared with harmonic tuning data obtained in experiments with real grating stimuli. The methods are illustrated using data recorded from one simple and one complex cell from the primary visual cortex of the monkey. The approach of transforming low-order kernels into predicted harmonic tuning functions provides a useful data reduction technique as well as providing insight into the interpretation of kernels.

Structural testing of multi-input linear-nonlinear cascade models for cells in macaque striate cortex.

Structural testing methods based on experimental white noise stimulus-response data were used to evaluate multi-input linear-nonlinear (LN) cascade models for simple and complex cells in macaque striate cortex. An LN structural test index, based on white noise stimulation, was developed and found to be suitable for classifying cells as simple vs complex. In particular, classification results based on the LN structural test index were similar to classification results based on a traditional modulation index derived from cell responses to drifting sinewave gratings. Judging from their structural test indices, complex cells deviated more strongly from LN behavior than did simple cells. Yet, even with simple cells, on average, only about 60% of the first- and second-order white noise stimulus-response relation was consistent with LN behavior. Just two of thirteen simple cells studied had an LN consistency level that exceeded 80%. Similar results were found in tests for consistency with an LNL model which includes an additional linear post-filter. We conclude that a conventional multi-input LN network model may be a useful approximation to the response behavior of some simple cells. However, even during steady state stimulus conditions, subcortical and/or cortical nonlinearities other than a static output nonlinearity play a very significant role in shaping the responses of most simple cells in the macaque striate cortex.

Interneuronal interaction between members of quadrature phase and anti-phase pairs in the cat's visual cortex.

Interactions between adjacent simple cells recorded simultaneously from the same microelectrode placement were studied by correlational analysis. The receptive fields of pairs of such cells exhibit either 90 degrees (quadrature phase) or 180 degrees (anti-phase) phase relationships. We now show that the majority of quadrature phase pair members do not receive common input from the immediately precedent stage along the visual pathway, nor do these cells interact with each other. The anti-phase pairs show relatively strong mutual inhibition. These results suggest that each of the physically adjacent phase-related simple cells receives excitatory input from a distinct group of pre-cortical cells, and that mutual inhibitions between members of anti-phase pairs are used to construct the inhibitory subzones of these cells. We propose a model which incorporates these new results and provides a parsimonious explanation for the construction of both quadrature phase and anti-phase pairs.

Theophylline pharmacokinetics: effect of continuous versus intermittent cimetidine i.v. infusion.

The comparative effects of continuous versus intermittent cimetidine infusion on theophylline pharmacokinetics were evaluated in 12 nonsmoking healthy male volunteers. Each subject received aminophylline 0.9 mg/kg/hr over 6 hours alone (control) and in random order at 1 week intervals, in combination with intermittent cimetidine (300 mg IV over 15 minutes every 6 hours) and continuous cimetidine (50 mg/hr IV) infusions. Both cimetidine regimens were administered for a total of 50 hours. Serial plasma samples were obtained and assayed for theophylline by HPLC. No significant differences existed in mean theophylline clearance and mean volume of distribution among control, intermittent or continuous cimetidine regimens; the power was greater than 80% to detect a 30% change in clearance. Only a minor difference in theophylline half-life between control and continuous cimetidine infusion (7.59 +/- 2.52 vs. 9.05 +/- 3.17 hr; P less than .05) was observed. These findings do not support a clinically significant interaction between IV aminophylline and cimetidine administered IV either as a low dose continuous infusion or as an intermittent infusion.

Structural classification of multi-input nonlinear systems.

We present new structural classification and parameter estimation results that are applicable to multi-input nonlinear systems. The mathematical relationships between the self- and cross-(Volterra and Wiener) kernels are derived for a basic two-input nonlinear structure. These results are then used to develop classification methods for more complicated two-input structures. Algorithms for estimating the parameters (linear and nonlinear subsystems) of these structures are also presented.

Spatial and temporal frequency selectivity of neurons in visual cortical area V3A of the macaque monkey.

Response properties of neurons in V3A were studied at a retinal eccentricity of 2-4 deg. The distributions of spatial frequency bandwidths and orientation bandwidths were similar to those of neurons in V1. Peaks of spatial frequency tuning curves ranged from 0.35 to 8.0 c/deg with a mean of 1.75 c/deg. Most V3A cells showed lowpass or, less often, broad bandpass temporal frequency selectivity. The mean direction selectivity index was 0.41. The response properties of cells in V3A differed most from those in V1 with respect to the larger receptive field widths in V3A averaging about 4 deg, the consequent larger number of cycles of the preferred grating that fall within the receptive field, and the previously reported profound response suppression incurred when patches of the preferred grating are extended both within and beyond the classical receptive field. The response properties of cells in V3A differed most from those in V3 in that V3A neurons are much less selective to the speed and direction of stimulus motion than are neurons in V3. The overall response properties of cells in V3A are consistent with anatomical evidence that places this cortical area in the visual pathway from V3A to V4 and then to IT.

Responses of simple and complex cells to compound sine-wave gratings.

We have studied the responses of simple and complex cells in the primary visual cortex of the cat to rigidly drifting compound sine-wave gratings as a function of the phase offset between fundamental and harmonic frequencies that both fell within the passband of the cell. Simple cells show phase-dependent increases and decreases in peak and mean response which are predictable on the basis of a cell's line weighting function. However, the amplitudes and phases of the base and harmonic frequencies in the response are, in general, not well predicted by the relationships of these same components in the compound grating stimuli. These distortions are shown to be largely a consequence of the rectification that follows linear summation at the simple cell stage. Such distortions are, in principle, correctable when the responses of a second simple cell, as part of a 180 deg phase pair, are taken into account. Complex cells typically showed a strong nonlinear response component at the difference frequency of drifting compound gratings. This was sometimes accompanied by a linear response component at one, or both, of the separate stimulus frequencies. Information about the absolute phases of the frequency components of a compound grating is not preserved in the nonlinear response of complex cells; however, information about the local phase difference between the gratings is preserved. In effect, the nonlinear component of the complex cell response is proportional to the time-varying signal envelope that results from the mutual interference of stimulus frequencies that fall in the cell's spatial receptive field and frequency passband.

Thrombocytopenia and vomiting due to difluoromethylornithine.

A 32-year-old Haitian male with acquired immunodeficiency syndrome presented with complications of Isospora belli enteritis. Therapy with the investigational drug difluoromethylornithine was initiated. Severe thrombocytopenia, nausea, and vomiting developed during intravenous drug therapy and recurred upon rechallenge with low-dose oral difluoromethylornithine. Therapy was discontinued because of these severe adverse effects.