Diabetic therapeutic effects of ethyl acetate fraction from the roots of Musa paradisiaca and seeds of Eugenia jambolana in streptozotocin-induced male diabetic rats.

The folklore medicine of primitive people has been greatly appreciated for centuries. Many researchers study the curative efficiency and mode of action of various medicinal plants. Serum glucose level, lipid profile, glucose tolerance, hepatic and muscle glycogen contents as well as the activities of hepatic hexokinase and glucose-6-phosphatase recovered significantly after oral administration of ethyl acetate fractions of Eugenia jambolana (E. jambolana) or Musa paradisiaca (M. paradisiaca) in separate (E. jambolana L.: 200 mg/kg of body weight and M. paradisiaca: 100 mg/kg of body weight) or combined form for 90 days (twice a day through gavage) to streptozotocin-induced diabetic rats. The loss in body weight of diabetic animals was reversed and serum levels of insulin as well as C-peptide, which were found to be reduced in diabetic rats, increased significantly after oral administration of the fractions. A histological study of the rats' pancreas revealed that after 90 days of oral treatment with the plant fractions in separate or combined form, the size and volume of pancreatic islets in diabetic treated rats increased significantly compared with the diabetic control group. Treatment of diabetic rats with the combined dose (300 mg/kg of body weight) of plant fractions (200 mg E. jambolana and 100 mg M. paradisiaca) was found to be more effective than treatment with the individual fraction. The doses of E. jambolana and M. paradisiaca selected for this study are the optimum antihyperglycemic doses of the plant fractions, which were determined after conducting a dose-dependent study at various dose levels (50-500 mg/kg) in our pilot experiments. The plant fractions were found to be free from metabolic toxicity. Through HPTLC finger printing, three different compounds were noted in the ethyl acetate fraction of E. jambolana L. and eight different compounds in the ethyl acetate fraction of M. paradisiaca L.

Auditory frequency discrimination in the white rat.

Frequency discrimination was investigated in the albino rat using a modified go/no-go positive reinforcement procedure in which subjects reported frequency increments in an ongoing series of pure tone bursts. Weber ratios (frequency difference limen/frequency) were measured from 5 to 32 kHz at 50 dB sound pressure level. A signal detection analysis of the procedure enabled a direct comparison to be made with the rat's performance in a discrete trial go/no-go task. A mean Weber ratio of 3.06+/-0.44% was measured in the frequency range 5-32 kHz. This indicates that the rat has better frequency discrimination acuity than has previously been thought. The result is discussed in the context of factors affecting performance. Among the factors that were explored we found that long training times and the specific training paradigm played important roles. In comparison to discrete trial go/no-go paradigms, rats performed much better when detecting signals from a repeating background. Frequency discrimination performance decreased linearly for tones less than 50 ms in duration. For longer tone duration performance was unaffected. The means and variability of reaction times for threshold changes of frequency were greater in comparison with supra-threshold frequency changes.

Simultaneous spectrophotometric analysis of a ternary mixture of pharmaceuticals--assay for meclozine hydrochloride, pyridoxine hydrochloride and caffeine.

Based on an extension of Vierordt's method and in continuation of earlier work, the simultaneous analysis of a ternary mixture of meclozine hydrochloride, pyridoxine hydrochloride and caffeine is discussed. Using 0.01 M methanolic sodium hydroxide as the solvent, the absorbance of the solution of the mixture is recorded at 230, 273 and 307 nm. The concentration of each component is determined by the solution of three simultaneous equations.

Reorganization in awake rat auditory cortex by local microstimulation and its effect on frequency-discrimination behavior.

In common with other sensory cortices, the mammalian primary auditory cortex (AI) demonstrates the capacity for large-scale reorganization following many experimental situations. For example, training animals in frequency-discrimination tasks has been shown to result in an increase in cortical frequency representation. Such central changes-most commonly, an increase in central representation of specific stimulus parameters-have been hypothesized to underlie the improvements in perceptual acuity (perceptual learning) seen in many learning situations. The actual behavioral relevance of central reorganizations, however, remains speculative. Here, we directly examine this issue. We first show that stimulating the AI cortex of the awake rat with a weak electric current (intracortical microstimulation or ICMS) has the effect of inducing central reorganizations similar to those accompanying the traditional plasticity experiments (a result previously noted only in anesthetized preparations). Depending on the site of AI stimulation, ICMS enlarged the cortical representation of certain frequencies. Next we examined the direct perceptual consequences of ICMS-induced AI reorganization for the rat's ability to discriminate frequencies. Over the course of the experiment, we also detailed, and made comparisons between, the frequency-response characteristics of rat AI cortex in the awake and ketamine-anesthetized animal. AI cells that responded to pure tones were divided into two categories--strongly and weakly responsive--based on the strength of their evoked discharge. Individual cells maintained their respective response strengths in both awake and anesthetized conditions. Strongly responsive cells showed at least four different temporal responses and tended to be narrowly tuned. Their responses were stable over the long term. In general frequency-response characteristics were qualitatively similar in the anesthetized and awake animal; bandwidths tended to be broader in awake animals. Although both strong and weak cell populations respond to tones, only the strongly responsive cells fit into a tonotopically organized scheme. By contrast, weakly responsive cells did not exhibit a frequency mapping and may represent a more diffuse input to AI than that underlying strongly responsive cells. In general, the overall frequency organization of AI was found to be equally well expressed in both the awake and anesthetized rat. ICMS reorganization of AI did not alter frequency-discrimination behavior in the rat--either signal detectability or response bias--suggesting that an increase in central representation, by itself, is insufficient to account for perceptual learning. It is likely that cortical reorganizations that accompany perceptual learning are strongly keyed to specific behavioral contexts.

A signal detection analysis of auditory-frequency discrimination in the rat.

The frequency-discrimination behavior of rats in a simple go/no-go task was analyzed using the theory of signal detection. Discrimination acuity was studied and the receiver operating characteristic (ROC) was generated in subjects by varying the reinforcement schedule and signal probability. The detectability indices d', A', and sensitivity index (SI) and response-bias indices B" and responsivity index (RI) were used to describe behavior. A' gave the most suitable psychometric functions while RI best described response-bias behavior. Weber ratios were 6.25% +/- 0.23% at 5 kHz in three subjects. The best method to obtain the ROC was to vary the probability with which subjects were reinforced. The ROC in two subjects demonstrated classical forms; in another subject, the function was asymmetric to the extent that detectability was not independent of response bias. Subjects altered their decision criterion in reporting a signal from trial to trial depending on previous trial events. On any given trial, subjects made a decision in one of several "decision states." Variables that influenced decision states included previous reinforcement and timeouts. The data indicate that timeouts may not be a useful feature in go/no-go tasks. The identification of multiple-decision states within a single behavioral session is a convenient method to generate the ROC without expressly manipulating experimental conditions.

Spectrophotometric estimation of rifampin-isoniazid mixture in dosage form.

A spectrophotometric method for the simultaneous determination of rifampin and isoniazid in dosage form is described. By using a mixture of methanol and water (2 + 3) as solvent, the absorbance of the mixtures of rifampin and isoniazid is measured at 264 nm and 335 nm. The concentration of each can then be calculated by solving 2 simultaneous equations. The procedure was successfully applied to a number of commercial samples; the results agreed well with those for compendial method.

Role of mammalian auditory cortex in the perception of elementary sound properties.

Studies in several mammalian species have demonstrated that bilateral ablations of the auditory cortex have little effect on simple sound intensity and frequency-based behaviors. In the rat, for example, early experiments have shown that auditory ablations result in virtually no effect on the rat's ability to either detect tones or discriminate frequencies. Such lesion experiments, however, typically examine an animal's performance some time after recovery from ablation surgery. As such, they demonstrate that the cortex is not essential for simple auditory behaviors in the long run. Our study further explores the role of cortex in basic auditory perception by examining whether the cortex is normally involved in these behaviors. In these experiments we reversibly inactivated the rat primary auditory cortex (AI) using the GABA agonist muscimol, while the animals performed a simple auditory task. At the same time we monitored the rat's auditory activity by recording auditory evoked potentials (AEP) from the cortical surface. In contrast to lesion studies, the rapid time course of these experimental conditions preclude reorganization of the auditory system that might otherwise compensate for the loss of cortical processing. Soon after bilateral muscimol application to their AI region, our rats exhibited an acute and profound inability to detect tones. After a few hours this state was followed by a gradual recovery of normal hearing, first of tone detection and, much later, of the ability to discriminate frequencies. Surface muscimol application, at the same time, drastically altered the normal rat AEP. Some of the normal AEP components vanished nearly instantaneously to unveil an underlying waveform, whose size was related to the severity of accompanying behavioral deficits. These results strongly suggest that the cortex is directly involved in basic acoustic processing. Along with observations from accompanying multiunit experiments that related the AEP to AI neuronal activity, our results suggest that a critical amount of activity in the auditory cortex is necessary for normal hearing. It is likely that the involvement of the cortex in simple auditory perceptions has hitherto not been clearly understood because of underlying recovery processes that, in the long-term, safeguard fundamental auditory abilities after cortical injury.

Simultaneous spectrophotometric determination of mefenamic acid and paracetamol in pharmaceutical preparations.

A spectrophotometric procedure for the simultaneous determination of mefenamic acid and paracetamol in a mixture is described. Using 0.01 M methanolic hydrochloric acid as solvent, the absorbance of the mixture is measured at 248, 279 and 351 nm. The concentration of each component can be calculated by solving two equations using two wavelengths, either 248 and 279 nm or 248 and 351 nm.

Recordings, behaviour and models related to corticothalamic feedback.

In this paper, we review recent work on aspects of corticothalamic interactions in the auditory and in the visual systems. There are gross similarities in the arrangements of these systems, but considerable contrasts in the processing computations and in the effects of corticothalamic feedback.