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Biomedical subjects

M H Lewis

Publications and source records attributed to M H Lewis.

At least 145 records · Page 8Linked to original sources
PubMed1987

Morbidity and mortality of common bile duct exploration.

This retrospective study reviews the complications which occurred in 257 patients who had supraduodenal exploration of the common bile duct in one hospital during a 15-year period. One hundred and eighteen patients (46 per cent) developed complications: septic and cardiorespiratory complications were most common, occurring in 19.5 per cent and 16.7 per cent of patients respectively. Postoperative retained stones were detected in 37 patients (14 per cent), causing complications in 54 per cent. Peroperative postexploratory cholangiography did not significantly reduce the incidence of this problem. None of the 12 patients who had postexploratory choledochoscopy had retained stones. Five patients (1.9 per cent) died, three of whom had duct procedures in addition to supraduodenal exploration and two of whom had retained stones. It is concluded that common bile duct exploration has a high associated morbidity, particularly due to sepsis and retained stones.

Adult↗
PubMed1987

A neurobiological alternative to the perceptual reinforcement hypothesis of stereotyped behavior: a commentary on "Self-stimulatory behavior and perceptual reinforcement".

A perceptual reinforcement theory of stereotyped movements is advanced by Lovaas, Newsom, and Hickman (1987) in an effort to integrate a number of diverse observations about the origins and maintenance of this behavior. We, in turn, argue that the theory, as presented, is logically flawed and fails to take into account important biological findings and theory concerning pathological stereotyped acts. An alternative theory, derived primarily from neurological concepts, is briefly described.

Autistic Disorder↗
PubMed1987

Neurotoxicants and central catecholamine systems.

The ubiquitous functional roles of brain catecholamines have led to the notion that in vitro neurochemical changes in these systems may predict neurotoxicity. Conversely, others have argued that the appropriate use of neurochemical methods is for testing specific hypotheses that are developed based on observed phenomena. Three studies from this laboratory are presented in support of the latter hypothesis. The first example is with inorganic lead, a major environmental pollutant. The effects of small doses of lead on CNS development have been difficult to quantify or study mechanistically. However, the serendipitous finding that lead exposure during early postnatal development increased lithium-induced polydipsia (LIP) has provided clues that have permitted testing of specific neurochemical hypotheses related to dopamine systems. Conversely, the administration of either trimethyl- or triethyltin to rats during perinatal periods causes profound neurotoxicity. However, although some changes in the neurochemistry of catecholamine systems have been found, these data have provided little insight into either the cause or sequelae of toxicity. Finally, the food color erythrosin (FD & C Red #3) was hypothesized to be a neurotoxicant because it disrupted neurotransmitter uptake in vitro. Our data suggested this was an artifact of the methodology, a position supported by clinical and behavioral studies. These data provide examples of the strengths and weaknesses in neurochemical approaches to neurotoxicity.

Animals↗
PubMed1987

Modified enzyme immunoassays for tobramycin using reduced sample and reagent volumes.

The accuracy of two modified enzyme immunoassay (EMIT) methods using reduced sample and reagent volumes for determining serum tobramycin concentrations was compared with that of the standard method. The modified EMIT assays used sample and reagent volumes of 25 and 30 microL instead of the standard 50-microL volumes. Solutions of tobramycin sulfate with known concentrations of 1, 2, 4, 8, and 12 mg/L were assayed five times using each of the three methods. Fourteen blood samples containing unknown concentrations of tobramycin were obtained from patients over a four-week period and assayed once by each method. The mean percentage recovery of tobramycin using the standard 50-microL sample-volume method (104.4 +/- 8.8%) was not significantly different from that of the 30-microL (106.6 +/- 9.9%) or the 25-microL (100.4 +/- 11.4%) assay method. There was good correlation between the standard method and the 25-microL (r = 0.993) and the 30-microL (r = 0.988) methods for determining unknown tobramycin concentrations. If the 25- and 30-microL assays were used in place of the standard 50-microL assay, costs would be reduced and the number of assays per kit would increase. The 30-microL and 25-microL sample and reagent volumes used in this study for the tobramycin EMIT assay allow substantial cost savings without a significant loss in accuracy.

Analysis of Variance↗
PubMed1987

Early experience with fine-needle aspiration cytology in a district general hospital.

The authors' early experience on introducing fine-needle aspiration cytology as a diagnostic aid into a district general hospital is presented. The use, benefits and criticisms of the technique in the assessment of breast lumps and lymphadenopathy and its peroperative applications are discussed. Results equivalent to those of specialist centres can be quickly attained.

Biopsy, Needle↗
PubMed1986

Motor effects of calcitonin administered intracerebroventricularly in the rat.

In rats treated with salmon calcitonin (CT) administered intracerebroventricularly (i.c.v., 85 or 8.5 pmol), spasmodic body movements, hopping and tail jerks, collectively termed dyskinesia, appeared within 1 h of administration and persisted for at least 24 h. In addition, spontaneous grooming, rearing and locomotion occurred less often in CT-treated rats than in vehicle-injected animals, while the incidence of both sniffing and nose poking remained essentially unchanged. The CT failed to displace either [3H]dopamine or [3H]spiperone from striatal membranes, and the behavioral effects were not blocked by haloperidol or SCH 23390, suggesting that the peptide did not directly affect dopamine receptors. The dyskinesia was not blocked by scopolamine, atropine, muscimol, diazepam or ketanserin. These data are consistent with the hypothesis that a compound with recognition characteristics similar to those of salmon CT may function as a neurotransmitter-modulator in the central nervous system.

Animals↗
PubMed1986

S(-)DP-5,6-ADTN as an in vivo dopamine receptor ligand: relation between displacement by dopamine agonists and their pharmacological effects.

The use of (-)DP-5,6-ADTN as a non-radioactively labeled ligand for an in vivo DA receptor assay is described and compared with racemic DP-5,6-ADTN, previously used for that purpose. The effects of four DA agonists (NPA, bromocriptine, DP-7-OH-ATN and 3-PPP) on the specific (-)DP-5,6-ADTN binding are related to their potencies to decrease striatal HVA concentrations and to induce stereotypy in rats. NPA and DP-7-OH-ATN caused a maximal decrease in HVA levels, when only a fraction of the receptors were occupied, while the occurrence of stereotypy was associated with a high receptor occupation, reflecting the higher affinity of these agonists for presynaptic than for postsynaptic receptors. Bromocriptine did not show this effect, as the dose-response relationships for HVA decrease, for induction of stereotypy and for the decrease in specific (-)DP-5,6-ADTN binding were all virtually equal to each other. While NPA and bromocriptine behaved as full postsynaptic agonists, in that maximal stereotyped behavior was observed after high doses, DP-7-OH-ATN was found to be a partial postsynaptic agonist, as it did not induce maximal stereotypy at a maximal receptor occupation. Racemic 3-PPP only caused a state of hypoactivity, but did neither affect specific (-)DP-5,6-ADTN binding nor striatal HVA levels. Our results are discussed in view of theories on the relation between receptor occupation and pharmacological effects and it is concluded that the in vivo receptor binding method using (-)DP-5,6-ADTN is a very useful tool for such investigations.

Animals↗
PubMed1986

Antagonistic behavioral effects of calcitonin and amphetamine in the rat.

Using an automated testing apparatus, the hypermotility induced by amphetamine had previously been found to be inhibited by intracerebroventricular (ICV) administration of salmon calcitonin (CT). The present study used a computer-supported direct observational method to characterize further the interactions of CT and amphetamine. After treatment with amphetamine (1.5 mg/kg, IP), the incidence of rearing, nose poking, and locomotion was reduced in rats that were pretreated with 85 pmol salmon CT ICV; the incidence of sniffing and grooming remained unchanged. CT-induced dyskinesia, a unique consequence of central CT treatment, was attenuated but not abolished by administration of amphetamine. These results support the premise that a compound with receptor recognition characteristics similar to those of salmon CT may act as a neurotransmitter-modulator in the central nervous system.

Amphetamine↗
PubMed1985

A computer-supported method for analyzing behavioral observations: studies with stereotypy.

The present report describes an observational method for quantifying behavior including drug-induced stereotypy, and employs an electronic data-collecting device with microcomputer hardware and software support. This method generates interval scale data, thus permitting the application of powerful parametric statistics, and also allows examination of discrete response topographies. For example, the method permits parametric comparisons among drug doses, treatment groups, as well as over time. The effects of the atypical antipsychotic drug thioridazine on apomorphine-induced stereotypy were used to illustrate the utility of the method. Thioridazine was found, among other effects, to potentiate apomorphine-induced gnawing and licking, while blocking sniffing.

Animals↗
PubMed1985

Comparison of venous and capillary blood sampling for the clinical determination of tobramycin serum concentrations.

Tobramycin concentrations have been determined in serum from capillary, venous and arterial blood samples taken from 16 patients during and after surgery. In 73 paired samples the concentrations in capillary samples were not significantly different from those measured in venous samples. The small concentration differences were neither dependent upon sampling time nor core-peripheral temperature differences. In 26 paired samples, concentrations in capillary samples were not significantly different from those determined in arterial samples. We conclude that concentrations in capillary samples are precise and unbiased estimators of venous concentrations and may be used in the adjustment of tobramycin dosage regimens.

Adult↗