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Biomedical subjects

M H Lewis

Publications and source records attributed to M H Lewis.

At least 19 recordsLinked to original sources
PubMed1992

Delayed presentation of an extradural abscess complicating thoracic extradural analgesia.

Extradural abscess is a rare but recognized complication of extradural anaesthesia. Previous reports have been associated with a short time interval between extradural catheterization and presentation. We report a patient with rheumatoid arthritis, receiving steroid therapy, in whom an extradural abscess did not present until 23 days after the insertion of a thoracic extradural catheter to provide postoperative analgesia.

Abscess↗
PubMed1992

A review of pancreatico-pleural fistula in pancreatitis and its management.

Pancreatico-pleural fistula is a rare condition in which pancreatic enzymes drain directly in to the pleural cavity, most commonly from an enlarging pseudocyst. We review the literature on the causes, investigations and treatment of pancreatico-pleural fistulae and compare this with our own experience of the case of a 41 year old man with a left sided pancreatico-pleural fistula associated with pancreatic duct obstruction. The fistula could not be demonstrated by USS, CT or ERCP, and after these investigations the patient was managed conservatively. However, deterioration in the patients' condition led to an urgent but not emergency laparotomy and operative pancreatogram. This demonstrated the distally obstructed pancreatic duct, with associated pleural fistula for which aggressive surgical intervention was indicated. The patient subsequently completely recovered.

Adult↗
PubMed1992

Evaluation of a new non-woven theatre swab.

A new non-woven theatre swab was compared with traditional gauze in laboratory and clinical studies. Results of both clinical and laboratory-based studies showed the non-woven swab to be as effective as traditional gauze in terms of softness, conformability, ability to pad or pack, resistance to snagging and shredding, and ease of counting when wet. The non-woven swabs were also superior to gauze with regard to their ability to retain fluid. Manufactured from polyester and hemisynthetic viscose, the non-woven swabs can be produced to a uniform standard and are less expensive. It is concluded that the new non-woven material has practical and economic advantages over traditional gauze.

Cellulose↗
PubMed1991

Dopamine receptor 'supersensitivity' occurring without receptor up-regulation.

Unilateral 6-hydroxydopamine (6-OHDA)-induced lesions of the substantia nigra have been widely used to study various aspects of dopamine neurobiology, and to screen for antiparkinsonian drugs. This study examined the role of receptor alterations in the pharmacological supersensitivity seen in response to lesioning of central dopamine pathways in rats by intracisternal (IC) administration of 6-OHDA (200 micrograms), as well as by bilateral (BIL) or unilateral (UNI) infusion of 6-OHDA into the substantia nigra (8 micrograms/side). Both IC and BIL lesions resulted in permanent decreases in dopamine concentration in the striatum, the major terminal projection from the substantia nigra. When challenged with apomorphine (0.3 mg/kg), IC-lesioned rats exhibited bursts of rapid locomotion interspersed by rearing, whereas BIL-lesioned rats displayed intense grooming or gnawing and nose poking of the cage floor; these behaviors were not seen in respective sham (i.e. vehicle)-lesioned rats injected with apomorphine. Scatchard analysis of saturation isotherms of both D1 [( 3H]SCH23390 binding sites) and D2 [( 3H]spiperone binding sites) dopamine receptors in the striatum revealed no difference in either the maximum number of binding sites (Bmax), or the dissociation constant (Kd) of either receptor type when BIL and IC lesioned rats were compared to appropriate controls. Conversely, the UNI lesioned rats had, under identical conditions of analysis, the expected increase in the density of D2 receptors on the lesioned side. There was no change in dopamine-sensitive adenylate cyclase activity in the striata of supersensitive IC-lesioned rats, but there was a shift to the left in the dose-response curve in striata from rats bilaterally-lesioned in the substantia nigra, similar to what occurs in UNI lesioned rats. Together, these data clearly demonstrate that although increases in receptor density and changes in cAMP systems are seen in the UNI model, neither mechanism is a requirement for functional supersensitivity in response to 6-OHDA lesions. These data suggest that other cellular events (e.g. alterations in receptor interactions) may play a role in the response to insult, and raise questions about the utility of the unilateral model as a screen for antiparkinsonian drugs.

Adenylyl Cyclases↗
PubMed1991

Oxygenation in the stomach and the effect of truncal vagotomy.

A Clark polarographic oxygen electrode allowed detailed mapping of tissue oxygen (PtO2) levels on the anterior surface of the stomach in five patients undergoing cholecystectomy. No significant difference in mean PtO2 was detectable between greater and lesser curvatures. A significant difference in mean PtO2 was detected between the body of the stomach and the pylorus (Mann-Whitney, P less than 0.01). The effect of truncal vagotomy on PtO2 was evaluated in six patients undergoing this procedure for duodenal ulceration. Mean postvagotomy stomach PtO2 levels (46 +/- 12 mmHg) were significantly lower (Wilcoxon test, P less than 0.001) than prevagotomy levels (59 +/- 14 mmHg). Truncal vagotomy did not have any significant effect on small intestinal PtO2. This work provides the first objective evidence of the relatively diminished tissue oxygenation in the gastric antrum and pyloric region, and confirms blood flow studies of the effects of vagotomy.

Adult↗
PubMed1991

Associative processes in differentially reared rhesus monkeys (Macaca mulatta): blocking.

Nine isolate and 6 socially reared adult rhesus monkeys were examined in a standard blocking procedure. A tone was paired with a startle stimulus (US) during Phase 1. A tone-light compound CS was paired with a US during Phase 2. In Phase 3, the light was presented alone to test for blocking. Results showed that learning about the light was blocked in social controls, but not in isolates. These data suggest isolates processed information atypically, in that they developed an association to a redundant cue. A second group of isolates (n = 3) underwent the identical procedures. However, conditioned reactions to the tone were extinguished before testing. Test responding was significantly reduced in this group, that is, blocking was obtained. These data suggest the within-compound association developed during Phase 2 mediated the isolate blocking deficit. Together, these findings imply long-term intellectual consequences of early social impoverishment. Such deficits may be mediated by alterations in central dopamine systems.

Animals↗
PubMed1991

The female brindled mouse as a model of Menkes' disease: the relationship of fur pattern to behavioral and neurochemical abnormalities.

The brindled mottled mutant mouse, a model of Menkes' disease, has alterations in copper homeostasis which cause, among other sequelae, neuronal degeneration in selected areas of brain. This work examined the neurochemical changes at postnatal days (PND) 15, 30 and 60 in females heterozygous for the sex-linked brindled mutation. These data were compared to behavioral alterations and to fur coat color at these same time points. The brindled heterozygotic females had lower concentrations of norepinephrine (NE) in the cingulate cortex, and higher levels of dopamine or dopamine metabolites in the cingulate cortex, thalamus and hypothalamus across all ages, although the difference was greatest at PND 15. The brindled females were much less active than their normal littermates at PND 15, but the differences were no longer evident at PND 30 and 60. Mottling of the fur is believed to result from low tyrosinase activity caused by abnormalities in copper metabolism. The fur pattern and behavior of the brindled mice were highly correlated with NE levels in the cingulate cortex and thalamus. These data show that female brindled mice have neurochemical abnormalities similar to (if less severe than) the male hemizygotes, that these abnormalities are regionally specific, are most apparent prior to 30 days of age, and are linked to behavioral deficits. These data also show that the extent of such deficits can be predicted by a quantitative analysis of the fur pattern of these females.

Age Factors↗
PubMed1991

Social deprivation of infant rhesus monkeys alters the chemoarchitecture of the brain: I. Subcortical regions.

Rhesus monkeys (Macaca mulatta) reared during the first year of life without social contact develop persistent stereotyped movements, self-directed behaviors, and psychosocial abnormalities, but neurobiological mechanisms underlying the behaviors of socially deprived (SD) monkeys are unknown. Monkeys were reared in total social deprivation for the first 9 months of life; control monkeys were reared socially (SR) with mothers and peers. Subjects were killed at 19-24 yr of age. Because the behaviors of SD monkeys are reminiscent of changes in striatal or amygdalar function, we used immunocytochemistry for substance P (SP), leucine-enkephalin (LENK), somatostatin, calbindin, and tyrosine hydroxylase (TH) to evaluate qualitatively and quantitatively patterns of neurotransmitter marker immunoreactivity within subcortical regions. In SD monkeys, the chemoarchitecture of the striatum was altered. Neuronal cell bodies and processes immunoreactive for SP and LENK were depleted markedly in patch (striosome) and matrix regions of the caudate nucleus and putamen; the average density of SP-immunoreactive neurons was reduced 58% relative to SR monkeys. Calbindin and TH immunoreactivities were diminished in the matrix of caudate and putamen of SD monkeys. TH-immunoreactive neurons, but not cresyl violet-stained neurons, in the substantia nigra pars compacta were decreased (43%) in SD monkeys. Peptide-immunoreactive terminals were reduced in the globus pallidus and substantia nigra in SD monkeys. The nucleus accumbens was the least affected of striatal regions. Striatal somatostatin immunoreactivity wa qualitatively and quantitatively similar in SD and SR monkeys. Several regions, for example, bed nucleus of the stria terminalis, amygdala, and basal forebrain magnocellular complex, that were in the same sections and are enriched in these markers did not appear altered in SD monkeys, suggesting a regional specificity for vulnerability. The altered chemoarchitecture of some basal ganglia regions in adult monkeys that experienced social deprivation as infants suggests that the postnatal maturation of neurotransmitter phenotypes in some structures is influenced by social environment. Abnormal motor and psychosocial behaviors resulting from this form of social/sensory deprivation may result from alterations in peptidergic and dopaminergic systems within the basal ganglia.

Amygdala↗
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↗
PubMed1991

Behavioral effects in the rat of dihydrexidine, a high-potency, full-efficacy D1 dopamine receptor agonist.

Dihydrexidine (trans-10,11-dihydroxy-5,6,6a,7,8,12b-hexahydrobenzo[a]phena nthridine) was reported recently to be the first full efficacy, potent D1 receptor agonist, but one also having some potency for D2 receptors. This study reports the effects of dihydrexidine on behavior of the rat. In study 1, the dose-response relationships of dihydrexidine (0.3 to 30 mg/kg) to various behaviors were assessed using direct observations. The frequency of three behaviors (grooming, sniffing, and locomotion) was significantly increased by this drug. The dose-response curve for drug-induced grooming approximated an inverted U shape. Dihydrexidine increased locomotion at two of the higher doses (3 and 30 mg/kg), and increased sniffing at doses greater than or equal to 1.0 mg/kg. Other behavioral topographies, such as licking, gnawing, and rearing, were not systematically affected by drug administration. Also, there was no indication of convulsion in any dihydrexidine-treated rat. In study 2, rats were pretreated with either the selective D1 antagonist SCH23390 or the selective D2 antagonist remoxipride prior to receiving dihydrexidine. SCH23390 antagonized the effects of dihydrexidine on grooming, locomotion, and sniffing. Conversely, remoxipride blocked dihydrexidine-induced locomotion, but had no effect on dihydrexidine-induced grooming or sniffing. Numerous behaviors are believed to be mediated by the interactions of D1 and D2 receptors. These data indicate that dihydrexidine can be an important tool for characterizing both the behavioral actions of D1 receptors, and the nature of D1/D2 interactions in mammalian brain. In addition, its high potency and full efficacy at D1 receptors, coupled with its significant D2 properties, may provide specific utility in certain clinical situations.

Animals↗
PubMed1990

Long-term effects of early social isolation in Macaca mulatta: changes in dopamine receptor function following apomorphine challenge.

The hypothesis that early social isolation results in long-term alterations in dopamine receptor sensitivity was tested using older adult rhesus monkeys. Isolated and control monkeys were challenged with apomorphine (0.1 and 0.3 mg/kg), and the drug effects on spontaneous blink rate, stereotyped behavior, and self-injurious behavior were quantified using observational measures. Monoamine metabolites were quantified from cisternal CSF by HPLC-EC, prior to pharmacological challenge. Isolated and control monkeys did not differ in CSF concentrations of HVA, 5-HIAA, or MHPG. At the higher dose, apomorphine significantly increased the rate of blinking, the occurrence of whole-body stereotypies, and the intensity of stereotyped behavior (as measured by observer ratings) in isolated monkeys. The frequency of occurrence of self-injurious behavior was too low to allow for meaningful comparisons. These significant differences in response to apomorphine challenge support the hypothesis that long-term or permanent alterations in dopamine receptor sensitivity, as assessed by drug challenge, are a consequence of early social deprivation.

Animals↗