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H L Williams

Publications and source records attributed to H L Williams.

At least 37 records · Page 2Linked to original sources
PubMed1988

Dose effects of methaqualone on stimulus encoding in a memory scanning task.

Three task variables, stimulus quality, memory set size and response type, were used in a Sternberg binary classification task to define stimulus encoding, short-term memory scanning, and response selection stages within a serial stage reaction process. Mean reaction times, and the slopes and intercepts of the function relating reaction time to memory set size, were used to test the hypothesis that performance deficits seen at two doses of methaqualone (2.9 mg/kg and 5.9 mg/kg), in the range formerly in common clinical use, were specific to the stimulus encoding stage of the reaction process. Mean reaction times were increased significantly by the methaqualone at both doses, but the effects of the two doses did not differ from one another. The intercept of reaction time as a function of set size showed significant main effects of methaqualone, stimulus quality, and response type, and a significant hyper-additive interaction of methaqualone with stimulus quality. At 2.9 mg/kg, the intercept was increased by methaqualone but only with degraded stimuli. At 5.9 mg/kg, the intercept was increased by methaqualone for both high and low quality stimuli. These results suggested a dose-dependent selective effect of methaqualone on the stimulus encoding stage of the reaction process.

Adult↗
PubMed1987

Effects of gepirone, an aryl-piperazine anxiolytic drug, on aggressive behavior and brain monoaminergic neurotransmission.

Gepirone (BMY 13805), a buspirone analog, was used to determine the antianxiety mechanism of the arylpiperazine class of drugs. Because of the weak effects of these drugs on conflict behavior, isolation-induced aggressive mice were used as the antianxiety model. Gepirone, like buspirone, potently inhibited attacks against group housed intruder mice (ED50 = 4.5 mg/kg i.p.) without causing sedation or ataxia. Inhibition of aggression was potentiated by co-administration of 0.25 mg/kg methiothepin or 2.5 mg/kg methysergide. Gepirone had variable effects on dopamine metabolism and reduced 5-hydroxytryptamine (5HT) metabolism about one third after a dose of 2.5 mg/kg. In contrast to buspirone, which markedly increased dopaminergic impulse flow, gepirone inhibited the firing of most cells recorded from the substantia nigra zona compacta in doses of 2.3-10 mg/kg i.v. and the effects were reversible by administration of haloperidol. The common metabolite of buspirone and gepirone, 1-(2-pyrimidinyl)-piperazine, caused increased firing rates only. Gepirone potently inhibited serotonergic impulse flow recorded from the dorsal raphe nucleus (88.3% after 0.04 mg/kg) and this effect was partially reversed by serotonergic antagonists. Both buspirone and gepirone displaced [3H]-5HT from the 5HT1a binding site in the hippocampus with IC50 values of 10 and 58 nM, respectively. Non-alkyl substituted aryl-piperazines displaced [3H]-5HT from both 5HT1a and 5HT1b binding sites. Thus, although gepirone may be a weak postsynaptic 5HT agonist, its primary effect is to decrease 5HT neurotransmission. In support of this conclusion was the observed potentiation of antiaggressive effects by blocking 5HT receptors wit small doses of methiothepin or methysergide, which would exacerbate the decreased release of 5HT caused by gepirone. These results are in harmony with reports that decreased serotonergic activity has anxiolytic-like effects in animal models of anxiety.

Aggression↗
PubMed1987

Effects of sodium intake during two parities on Na status in blackface sheep.

A low-sodium diet was given to Blackface ewes over two reproductive seasons. This diet provided a total of 3-7 mmol/d except during lactation when the intake was about 11 mmol/d. Control ewes were given the same diet supplemented with sodium chloride to provide recommended levels which were about tenfold that of the experimental diet. The output of Na in urine and faeces from ewes given the low-Na diet was very low, about 3 mmol/d, from early in the experiment and continued at about this level throughout. Lambs born to low-Na ewes and given a low-Na diet similar to that of their dams during lactation, grew, after weaning, more slowly than corresponding lambs from control ewes, but at 6 months of age when six from each group were killed, tissue Na contents were only slightly lower in experimental than control lambs. Fluids and tissues obtained at the end of the second lactation from four ewes of each group that had suckled twin lambs, were analysed for Na and potassium. The Na concentration in saliva and rumen fluid of low-Na ewes was about half that of control ewes and there were corresponding increases in K: the differences were significant. Although Na concentrations for experimental ewes were generally lower than those for control ewes in the tissues analysed (liver, kidney, heart, brain and bone), the difference was significant only for the heart (P less than 0.05). Haemoglobin and packed cell volume were significantly elevated in low-Na ewes (P less than 0.01), indicating decreased body fluid volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of sodium intake on lactation and Na levels in body fluids of Blackface ewes.

1. A low-sodium diet was given to Blackface ewes over two reproductive seasons; the diet provided 3-7 mmol Na daily, except for the period of lactation, when Na intake was increased to around 11 mmol/d. The diet of the control ewes was supplemented with sodium chloride to provide the recommended allowance of about ten times the level in the experimental low-Na diet. 2. Milk production was assessed during the first 2 months of lactation from incremental changes in the live weight of lambs during controlled sucking periods. Na and potassium were determined in milk and also in plasma, saliva and urine. 3. Neither yield nor concentration of Na and K in milk was affected by the level of Na in the diet. These results were supported by the similarity in live-weight gain of lambs in both years regardless of diet. 4. Plasma Na and K concentrations were not affected by the level of dietary Na. Na concentration in saliva and urine was significantly lower in the treated than in the control ewes, and K concentration in saliva was significantly higher.

Animals↗
PubMed1984

Postnatal development of the brainstem auditory evoked potential and far-field cochlear microphonic in non-sedated rat pups.

Normal postnatal development of the scalp-recorded cochlear microphonic (CM) response and brainstem auditory evoked potential (BAEP) were studied in rat pups. BAEP latencies decreased and amplitudes increased as a function of maturation. These changes occurred rapidly between 14 and 23 days of age with gradual change occurring thereafter. The observed latency changes indicated that the auditory pathway matures in a sequential manner from the most peripheral to the most rostral structures. For example, CM latency stabilized (matured) by day 17 while BAEP wave I and II latencies stabilized by days 23 and 35, respectively. BAEP waves III and IV still showed significant latency decreases between days 42 and 70. The between-litter variability for CM and BAEP wave latencies also decreased with age. In contrast to peak latency measures, CM and BAEP amplitudes followed an independent time course of postnatal development. CM amplitude did not increase significantly after day 14. Amplitudes of all 4 BAEP components increased steadily from day 14 to 29, then stabilized. Unlike latency variability, amplitude variability was independent of age. There were no significant gender-dependent differences in amplitudes or latencies between the ages of 14 and 70 days.

Age Factors↗
PubMed1984

Brain-stem auditory evoked potentials in the rat: effects of gender, stimulus characteristics and ethanol sedation.

Rat BAEPs varied significantly as a function of gender and ethanol sedation as well as stimulus intensity and repetition rate. All BAEP wave latencies decreased and amplitudes increased with increasing stimulus intensity. Contrary to the prevailing view, the I-IV interpeak latency changed significantly as a function of stimulus intensity. In terms of repetition rate, all BAEP wave latencies increased and amplitudes decreased with increasing repetition rate. Male rats, compared to females, had significantly longer latencies for several BAEP components and interpeak latencies as well as smaller wave II amplitudes across a broad range of stimulus intensities. Males, compared to females, also had longer BAEP wave IV latencies and I-IV interpeak latencies at a slow stimulus repetition rate (8 clicks/sec) but shorter wave IV and I-IV latencies at a fast repetition rate (120 clicks/sec). These gender-dependent differences indicate that male and female rat BAEP data should not be combined indiscriminantly. Ethanol sedation had a statistically significant effect on the I-IV interpeak latency that was judged to be largely independent of core temperature changes. This finding suggests that while sedatives and anesthetics used to immobilize animals may have apparently minor temperature-independent effects on BAEP latencies, these effects can be statistically significant.

Animals↗
PubMed1984

Effect of alcohol on recall and recognition as functions of processing levels.

Other investigators have suggested that the memory impairments found in alcohol intoxication represent the failure to process information to sufficient depth, i.e., an encoding deficit. The present study employed different processing levels (semantic, phonemic and graphemic) in intentional-learning experiments to examine the effects of two different doses of alcohol on verbal free recall and recognition. Alcohol significantly impaired both recall and recognition. Guiding processing at information input with semantic orienting tasks and at retrieval with recognition testing improved the retention performance of both intoxicated subjects and controls administered a placebo. However, neither procedure corrected the relative decrement associated with the higher of the two doses of alcohol. Alcohol intoxication had no effect on the speed or accuracy of the initial encoding of items at any processing level. The results offer no support for the view that the verbal-retention deficits associated with alcohol intoxication are related either to the spontaneous failure to undertake deep semantic processing or to the inability to do so.

Adult↗
PubMed1983

Secobarbital effects on recall and recognition in a levels-of-processing paradigm.

Dose effects of secobarbital on free recall and recognition of words were examined in levels-of-processing paradigms. Secobarbital significantly impaired recall, even when initial item processing was guided with appropriate orienting tasks. However, when processing was guided both at input (with orienting tasks) and at retrieval (with recognition testing), secobarbital-related retention deficits reported in conventional 'learn these words' experiments were not found. Levels-of-processing theory suggests at least two possible mediators for retention deficits associated with drug intoxication, a production deficit at encoding or reduced processing capacity. Neither of these hypotheses can account for the data. A third hypothesis suggests that the intoxicated subject adopts a cautious response-decision strategy, thus failing to emit available items in recall testing or to endorse correct items on recognition. The results of signal detection analysis offered no support for this hypothesis. Considered together with earlier studies, the data indicate that when processing is guided only at retrieval, secobarbital produces both recall and recognition decrements. On the other hand, when processing is guided only at input, the drug produces recall deficits. Apparently, when secobarbital-intoxicated subjects are left to generate their own responses at retrieval, they fail to undertake optimal retrieval strategies. When their processing is guided both at input and retrieval, their drug-induced retention decrements can be corrected.

Adult↗
PubMed1981

Dose effects of secobarbital in a Sternberg memory scanning task.

Mean reaction times obtained in a Sternberg memory-scanning task were examined for the effects of secobarbital at two doses (1.47 mg/kg and 2.94 mg/kg) spanning the dose range commonly used in clinical practice. Both doses slowed reaction time significantly, with a more pronounced effect at the higher dose. The discriminability of the probe stimulus interacted with the barbiturate, producing a hyperadditive effect on reaction time, but only at the high dose. There were no other significant interaction effects involving the drug. These data are interpreted as additional support for an hypothesis localizing the effects of secobarbital to stimulus-encoding stages in the reaction process.

Adult↗
PubMed1981

Altered sleep physiology in chronic alcoholics: reversal with abstinence.

Somnograms obtained from recently abstinent chronic alcoholics reveal gross disruption succinctly described as "fractured" sleep. Sleep onset is delayed and the rhythmic properties of the sleep pattern are markedly disturbed with numerous brief arousals and changes of sleep stage. Excessive stage 1 and stage rapid eye movement sleep are present while the high voltage slow wave sleep is markedly reduced or absent. With continued sobriety (9 mo or more) the sleep stage percentages tend to return to normal levels, but the disruption of the sleep pattern persists after as much as 21 mo of abstinence.

Adult↗
PubMed1980

Improved radiochemical method for measuring ferrochelatase activity.

We describe a radiochemical method for measuring ferrochelatase activity in the in vitro incorporation of iron into mesoporphyrin-IX to form mesoheme. 59Fe is used to quantify ferrochelatase activity in rat liver. The uptake of iron is linearly related to the time allowed for it to occur, and the reaction proceeds optimally under reducing and anerobic conditions, maintained in sealed lyophilization vials under a positive pressure of nitrogen.

Animals↗