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Biomedical subjects

A McLean

Publications and source records attributed to A McLean.

At least 163 records · Page 9Linked to original sources
PubMed1973

Enzymes involved in phenylalanine metabolism in the human foetus and child.

The activities of phenylalanine p-hydroxylase, tyrosine: alpha-ketoglutarate and phenylalanine: pyruvate aminotransferases, and aromatic alpha-ketoacid reductase have been measured in liver biopsies obtained from children with a series of disorders other than phenylketonuria and from human foetuses aged 8.5 to 24 weeks. The importance of such a study in relation to the management of infants with hyperphenylalaninaemia and pregnant phenylketonuric women is discussed

Child↗
PubMed1967

The innervation of sheep mesenteric veins.

1. An isolated preparation of sheep mesenteric vein is described from which contractions of the longitudinal smooth muscle of the adventitia have been recorded in response to stimulation of intramural and periarterial nerves.2. The preparation did not respond to single stimuli but the relation between amplitude of response and frequency of stimulation was characteristic of that described for other smooth muscles innervated by sympathetic nerves.3. Responses were blocked by tetrodotoxin, guanethidine, and by a number of alpha-receptor blocking drugs. Responses to peri-arterial stimulation were unaffected by hexamethonium. It was concluded that the longitudinal smooth muscle is supplied with post-ganglionic noradrenergic motor nerves and the presence of such fibres in the adventitia was confirmed by fluorescence microscopy.4. Acetylcholine also caused contractions. Although a direct excitatory action on the smooth muscle could not be excluded, results suggest that acetylcholine may release noradrenaline from the axons of the sympathetic ground plexus.

Acetylcholine↗
PubMed1966

The structure and deposition of human-liver glycogens.

1. Glycogen was extracted from and the amount determined in human foetal livers ranging in age from 13(1/2) to 26 weeks. 2. The detailed structures of human foetal- and child-liver glycogens were examined and shown to be essentially the same. 3. The deposition of glycogen in different mammalian species is discussed.

Amylases↗
PubMedDate not supplied

Innovations in neonatal case management: an integrated, data-driven approach.

The intent of this article is to provide one company's perspective on the challenging and complex care management of the high-risk neonate. The strategies presented herein should enable and encourage case managers to implement an integrated management process for the frail neonatal population.

Case Management↗
PubMedDate not supplied

Influence of food intake on presystemic clearance of drugs.

Many drugs have a low degree of oral bioavailability even though their gastrointestinal absorption is complete. This is because they undergo extensive presystemic metabolic transformation during the first passage of the drug through the gastrointestinal mucosa and the liver. In addition to effects on the absorption of some drugs, food intake has been found to influence the bioavailability of drugs with extensive presystemic metabolic clearance. Extensive presystemic clearance occurs commonly with compounds that are lipophilic bases, e.g. propranolol and amitriptyline, but rarely if ever with lipophilic acids, e.g. salicylic acid and penicillin, except for esters of such acids, e.g. acetylsalicylic acid (aspirin) and pivampicillin. While presystemic clearance of (esterified) acidic drugs is unaffected by food, concurrent food intake markedly reduces presystemic clearance, and thus enhances bioavailability, of several lipophilic bases. Among these are propranolol, metoprolol, labetalol, dixyrazine and hydralazine, which are presystemically metabolised by hydroxylation, glucuronidation and acetylation enzymes systems. In contrast, the bioavailability of lipophilic bases which undergo presystemic dealkylation (amitriptyline, codeine, dextropropoxyphene, prazosin, zimelidine) is unaffected by concurrent food intake. Food intake reduces presystemic clearance of hydralazine and propranolol when these drugs are administered in conventional rapid-release tablets but not when they are given in slow-release formulations. Likewise, coadministration of hydralazine reduces presystemic clearance of rapid-release but not slow-release propranolol. These and other observations favour the view that food may reduce presystemic clearance of (certain) lipophilic basic drugs via transient, complex effects on splanchnic-hepatic blood flow and/or shunt processes, and that the extent of this effect is influenced by the rate of drug delivery to the liver. In addition, these findings refute the notion that the reduced presystemic clearance results from (long-lasting) hepatic enzyme inhibition by some nutrient. On the other hand, repeated intake of specific nutrients (protein) and food contaminants (benzpyrene) can enhance presystemic drug clearance by enzyme induction. Thus, food may exert a dual effect on presystemic drug clearance. A complete evaluation of the influence of food on presystemic drug clearance necessitates bioavailability studies carried out following both single and repeated meals, including different kinds of food prepared by various cooking methods. The influence of food on the presystemic clearance of drugs is most likely to be clinically relevant with drugs having narrow therapeutic margins and/or steep dose-response curves.

Biological Availability↗