Factors affecting serum oxytetracycline levels in beef calves

Fifteen Aberdeen Angus steers, 295-364 kg, were dosed with either 4.4 or 11 mg of oxytetracycline hydrochloride/kg im. The antimicrobial activity of the serum was determined periodically, and the resulting data were treated statistically to determine the sources of variation. Variance in serum levels of oxytetracycline activity was attributed to dose, time of bleeding, order of dosing, animal, and assay. The total variance component was proportionately greater for the 11-mg/kg dose than for the 4.4-mg/kg dose. Animal variance increased with the higher dose level of oxytetracycline. The influence of dose on serum level was tested by applying a t test to the mean serum levels and their standard deviations at each bleeding time. The 4.4- and 11-mg/kg serum levels were significantly different (p less than 0.01) at all bleeding times. The 4.4-mg/kg serum levels mutliplied by 2.5 were not significantly different (p less than 0.05) from the 11-mg/kg serum levels at all bleeding times.     

Chlorpropamide-induced thrombocytopenia

Thrombocytopenia is a rare complication of chlorpropamide therapy. An immunological mechanism is generally held responsible, but has never previously been proved. In the present case the existence of such a mechanism has been established.     

Synchronous period-doubling in flicker vision of salamander and man

Periodic flashes of light have long served to probe the temporal properties of the visual system. Here we show that during rapid flicker of high contrast and intensity the eye reports to the brain only every other flash of light. In this regime, retinal ganglion cells of the salamander fire spikes on alternating flashes. Neurons across the entire retina are locked to the same flashes. The effect depends sharply on contrast and flash frequency. It results from a period-doubling bifurcation in retinal processing, and a simple model of nonlinear feedback reproduces the phenomenon. Pharmacological studies indicate that the critical feedback interactions require only cone photoreceptors and bipolar cells. Analogous period-doubling is observed in the human visual system. Under bright full-field flicker, the electroretinogram (ERG) shows a regime of period-doubling between 30 and 70 Hz. In visual evoked potentials from the occiput, the subharmonic component is even stronger. By analyzing the accompanying perceptual effects, we find that retinal period-doubling begins in the periphery of the visual field, and that it is the cause of a long mysterious illusory flicker pattern.     

Increased density of microtubule associated protein 2-immunoreactive neurons in the prefrontal white matter of schizophrenic subjects

Recent studies have suggested that schizophrenia may be related to prenatal disturbances in the cortical subplate, a transient but essential structure in the formation of cerebral cortical circuitry. Although most subplate neurons die during later development, some remain as the interstitial neurons of the adult white matter. In this study we used a monoclonal antibody against the cytoskeletal protein, microtubule associated protein-2 (MAP2), to quantify the density and distribution of labeled neurons in postmortem brain specimens containing the prefrontal white matter from five schizophrenic cases and matched controls. In both schizophrenics and matched controls, the density of white matter neurons decreased with increasing white matter depth. However, the mean density of MAP2-immunoreactive neurons was greater in the superficial white matter of the schizophrenic subjects compared to the matched controls. In contrast, no difference in the density of labeled neurons was seen in the deeper white matter. These findings are consistent with an abnormality in the development of the cortical subplate in at least some cases of schizophrenia.     

In vitro 2,3,7,8-tetrachlorodibenzo-p-dioxin interference with the anterior pituitary hormone adrenocorticortropin

Pharmacological effects of acute treatment with venlafaxine (VEN), a clinically active antidepressant [a noradrenaline (NA) and 5-hydroxytryptamine (5-HT) reuptake inhibitor without any affinity for neurotransmitter receptors] were studied in mice and rats. VEN inhibited the reserpine- or apomorphine-induced hypothermia and enhanced the L-5-HTP-induced head twitches in mice. It reduced the immobility time in Porsolt's test in mice and rats, but either did not change the locomotor activity (mice) or decreased it (rats). VEN reduced the locomotor hyperactivity induced by amphetamine (AMP), apomorphine (APO) and quinpirole (QUI), as well as the APO-induced stereotypy; the stereotypy induced by AMP in rats was prolonged. VEN neither changed the clonidine-induced aggressiveness in mice nor the behavioral syndrome induced by oxotremorine in rats. The obtained results indicate that VEN, given acutely, shows a pharmacological profile similar to that of tricyclic NA and 5-HT reuptake inhibitors. In contrast to the antidepressants mentioned above, VEN does not exhibit an alpha 1-adrenolytic or a cholinolytic activity (in vivo tests).     

Performance of administrators, professionals, and paraprofessionals during community-based brain injury rehabilitation training

OBJECTIVE: Two related studies that evaluated the impact of a continuing education program about community-based rehabilitation on the performance of administrators, professionals, and paraprofessionals are presented. One study contained a second part that examined whether differences between pre-course test performance and post-course test performance might be accounted for by practice effects. DESIGN: Factorial mixed model designs. SETTING: University classroom. PARTICIPANTS: Three hundred and eight professionals, administrators, and paraprofessionals from a variety of community-based rehabilitation programs. INTERVENTION: The 4-day graduate-level course focused on three content areas: brain and behavior relationships, behavioral and cognitive intervention strategies, and a rehabilitation philosophy that emphasizes individual client rights. MAIN OUTCOME MEASURE: An examination completed before and immediately after taking the course. RESULTS: Professionals and administrators perform better than paraprofessionals when tested at the beginning and end of the training. However, the absolute differences among these groups were not substantial. In addition, the rate of learning course content was the same for administrators, paraprofessionals, and professionals. CONCLUSIONS: The results support the usefulness of training for all levels of staff and suggest that all levels of staff benefit in an equal fashion.