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Biomedical subjects

M S Lawrence

Publications and source records attributed to M S Lawrence.

At least 19 recordsLinked to original sources
PubMed1991

The D1 receptor antagonist, SCH 23390, induces signs of parkinsonism in African green monkeys.

Systemic administration of the selective D1 antagonist, SCH 23390, caused significant motor changes in healthy African green monkeys. The effects included the parkinsonian signs of motor freezing, incoordination, bradykinesia, poverty of movement, tremor and depressed blink rate. SCH 23390 administered to MPTP-treated monkeys increased existing parkinsonism. The results are of particular interest in light of recent data that demonstrate the effectiveness of dihydrexidine, a full D1 agonist, in alleviating parkinsonism in MPTP-treated monkeys. These data implicate D1 receptors in the functions impaired by Parkinson's disease and suggest the possibility of parkinsonian side effects in the clinical use of this or similar D1 antagonists as treatments for psychiatric disorders.

Analysis of Variance↗
PubMed1991

MPTP lesions and dopaminergic drugs alter eye blink rate in African green monkeys.

Eye blink rates were studied in African green monkeys following relatively specific destruction of substantia nigra and its dopamine projections with the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Monkeys treated with MPTP had a significantly lower blink rate than controls over a period from two to five and a half months after treatment. Furthermore, the degree of parkinsonism expressed in treated animals was inversely correlated with blink rate. Pharmacologic studies further supported the role of dopamine receptors in the regulation of blink rate. PHNO (4-propyl-9-hydroxynaphoxazine), a potent and highly specific D2 agonist, effective in alleviating parkinsonism, caused a significant transient increase in blink rate, while sulpiride, a D2 antagonist, caused a decrease and blocked the effect of PHNO. Apomorphine and haloperidol, although less specific, had potent and predictable effects based on their interactions with dopamine systems. Blink rate may provide a nonintrusive measure of central dopamine activity that would help to evaluate the progress of Parkinson's disease or treatments which attempt to restore dopamine function.

Animals↗
PubMed1991

D1 and D2 dopamine receptors independently regulate spontaneous blink rate in the vervet monkey.

Previous studies have revealed the involvement of a dopaminergic link in the regulation of spontaneous eye blink rate in primates. Based on the effect of dopamine D2 receptor-selective drugs and the anecdotal failure of the partial D1 agonist, SKF 38393, to alter blink rate in monkeys, it was assumed that D1 dopamine receptors did not control blink rate. The recent availability of dihydrexidine, a full D1 agonist, prompted us to reevaluate the role of D1 and D2 receptors in the regulation of blink rate. African green monkeys (n = 5) were used in all studies. Dihydrexidine produced a rapid and dose-dependent (up to 1 mg/kg, i.m.) increase in blink rate. The elevation in blink rate elicited by 0.3 mg/kg dihydrexidine was completely reversed by prior administration of a specific D1 antagonist, SCH 23390 (0.01 mg/kg, i.m.), but was unaffected by prior administration of a specific D2 antagonist, remoxipride (1 mg/kg, i.m.). Treatment with the specific D2 agonist, (+)-4-propyl-9-hydroxynaphthoxazine, led to a rapid and dose-dependent (up to 0.01 mg/kg, i.m.) increase in blink rate. The raised blink rate produced by (+)-4-propyl-9-hydroxynaphthoxazine (0.001 mg/kg) was abolished by pretreatment with remoxipride, but was not influenced by pretreatment with SCH 23390. These data indicate that spontaneous blink rate in the primate can be regulated by both D1 and D2 dopamine receptors. Furthermore, the receptor subtypes appear to affect blink rate in the same direction, yet function independently. Measurement of blink rate may provide a noninvasive method to assess the potency and selectivity of dopamine agonists and antagonists in primates.

Animals↗
PubMed1985

List size, screening methods, and other characteristics of practices in relation to preventive care.

Twenty eight practices carried out a review of patient records for information about preventive procedures on two occasions in 1980 and 1982. We have now undertaken a survey of certain characteristics of the practices in an attempt to demonstrate features associated with effective preventive care. Significant favourable factors are a small list size, the setting up of a formal screening programme for cervical cytology and measuring blood pressure, and few registered patients in social classes IV and V. More successful practices also tend to be training practices, have principals with higher qualifications, and have developed good records organization. Opportunistic screening for cervical cytology and measuring blood pressure was not shown to be more effective than no policy of screening at all.

Adolescent↗
PubMed1984

Effect of gentamicin and dexamethasone on the natural history of the rat Escherichia coli brain abscess model with histopathological correlation.

In a rodent model of Escherichia coli brain abscess, the natural history of the infection was studied and the influence of a glucocorticoid (dexamethasone) and an antibiotic (gentamicin) on the development of brain abscess and the survival of abscess-bearing animals was evaluated. The administration of steroids using three different dosage schedules suppressed the macrophage and glial response, decreased collagen formation, increased the number of pathologically evident bacteria, and decreased host survival. The administration of antibiotics by parenteral routes decreased the number of viable bacteria in the abscess. The simultaneous administration of systemic gentamicin and dexamethasone resulted in increased host survival to a level that was intermediate between that of animals treated with dexamethasone alone and that of those treated with gentamicin alone. Thus, some of the adverse effect of corticosteroids on host survival could be mitigated by the simultaneous administration of antibiotics. Finally, it was observed that the abscess in this model tends to expand along white matter tracks. This path of least resistance may be responsible for the observation that brain abscesses tend to rupture into the ventricle rather than into the subarachnoid space via the cortex.

Animals↗
PubMed1983

Impact of audit on preventive measures.

The results of two reviews of practice records for information about various preventive measures are reported. The reviews were conducted two and a half years apart in the same 29 practices, on roughly 6500 records on each occasion. The first review was carried out during a postgraduate education course involving audit. Two main analyses were undertaken: one concerned with the entire record sample and the other with the individual practice results. Important and substantial improvements were shown in both analyses, which were spread throughout the practices and were not confined to practices at the lower end of the range simply "catching up." The change between the reviews in the mean recorded rates for cervical cytology was 56% to 64%; for rubella immunity 28% to 40%; for polio immunity in adults 15% to 21%; for completed primary immunisation 68% to 78%; for recorded blood pressure 53% to 61%; and for smoking information 22% to 30%. Improvement has been steady but the rate of improvement, especially for recording blood pressure and rubella immunity, has increased since the postgraduate education course.

Adolescent↗
PubMed1981

An evaluation of recorded information about preventive measures in 38 practices.

This paper reports the results of a review of practice records for information about various preventive measures; 8,500 records from 38 practices were studied. In collecting the data a Practice Activity Analysis data sheet was used.The results are presented in a way which makes it possible for others undertaking these analyses to compare their results with those reported here. They point to a number of conclusions, in particular:1. Much less cervical cytology has been done for women in their 50s than for those in their 30s and 40s; in particular 45 per cent of women in their 50s have never had a smear.2. Only 35 per cent of girls aged 15 to 19 were known to be immune to rubella.3. Only 14 per cent of adults aged 20 to 40 were known to be immune to polio.4. Of men in their 40s, 47 per cent had no record of their blood pressure having been taken during the previous 10 years.5. Information about smoking habits was available in 23 per cent of records.

Adolescent↗