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Biomedical subjects

M Tyler

Publications and source records attributed to M Tyler.

At least 19 recordsLinked to original sources
PubMed1995

Ear reduction.

Four cases of ear reduction for congenital macrotia and ear asymmetry are presented. To minimize the visible scarring the technique of helical advancement was used. The indications for this uncommon procedure are discussed with a review of the literature. This simple technique has been effective in achieving the desired reduction, leaving the scar hidden in the eaves of the helix, and we endorse its wider use.

Adult↗
PubMed1995

Correlates of left-handedness in a large sample of schizophrenic patients.

Questionnaire data concerning hand preference from the parents of 686 schizophrenic patients were used to test predictions relevant to neurodevelopmental models of schizophrenia. In line with predictions, left-handed patients (n = 94) had a more frequent history of difficult birth, more childhood cognitive and behavioural abnormalities and more persistent auditory hallucinations than did right-handed patients.

Adolescent↗
PubMed1995

Regeneration after in situ flushing of partially hepatectomised rat livers.

The effect of various components of the transplant procedure upon the regenerative process in reduced liver grafts is not known. In this study, partially hepatectomised rat liver remnants were flushed with 5 ml of either Ringer's lactate, Euro Collins solution or University of Wisconsin solution at 4 degrees C and then 5 ml Ringer's lactate at 4 degrees C. After partial hepatectomy alone, the peak increase in thymidine kinase was measured at 24 hours (36,021 +/- 8,060 disintegrations per minute per milligram protein; the mitotic index was 25 +/- 7). In all the groups in which the remnant was flushed, peak thymidine kinase and mitotic index were measured at 48 hours. The pattern of ornithine decarboxylase activity was disorganised in all groups. Flushing of the liver remnant therefore delays the regenerative response by 24 hours. In large animals, including humans, regeneration appears to commence within the first 5 days after resection. A comparable delay doubling this time might coincide with the onset of rejection and further compromise liver function.

Animals↗
PubMed1994

The effect of administration of FK506 on delayed regeneration in flushed partially hepatectomized livers.

It has been shown previously that liver regeneration after partial hepatectomy in rats is delayed if the liver is subjected to either concurrent ischaemia, flushing with cold solution, or grafting. We have shown recently that treatment with CsA preoperatively overcomes the suppressive effect of flushing and returns the regenerative response to a normal time scale. The present study was designed to investigate whether administration of FK506 would also return the observed delayed regenerative response to normal. Long-Evans rats weighing 250-350 g were subjected to standard 68% partial hepatectomy. Group 1 had no further treatment; in group 2, the liver remnant was flushed with 10 ml cold (4 degrees C) Ringers lactate solution, and in group 3, FK506 (1 mg/kg/day) was administered by intramuscular injection for 3 days before the partial hepatectomy and flushing as in group 2; a final dose was given after completion of the procedures. Animals were killed in sets of 6 per group at 4, 24, 48, 72, and 96 hr after surgery and blood samples were taken for measurement of plasma aspartate amino-transferase. Liver biopsies were analyzed for measurement of thymidine kinase and ornithine decarboxylase activity and for counting of mitotic figures. While the highest recorded thymidine kinase activity occurred in group 1 at 24 hr, this was delayed to 48 hr in both group 2 and 3 and counts remained high up to 96 hr in group 3. Mitotic indices were only significantly elevated (compared with group 1 at 96 hr), while ornithine decarboxylase activity did not correlate with these changes being significantly lower than in groups 2 and 3 at 4 hr and in group 3 also at 24 hr. Plasma aspartate aminotransferase was also significantly higher in group 3. It is concluded that the administration of FK506 preoperatively to rats subjected to partial hepatectomy and flushing did not restore the delayed regenerative response to normal but enhanced the response (as measured by thymidine kinase but not by mitotic indices) which commenced at 48 hr and was still present at 96 hr.

Animals↗
PubMed1994

Does liver transplantation in the rat cause a regenerative response. The effect of arterialisation of the graft.

This study was conducted to determine the pattern of early regenerative response to orthotopic intact liver transplantation in the rat and to investigate whether the response differed in grafts with or without revascularisation of the arterial bed. Outbred male Long Evans (LE-LE allogeneic, non rejector) rats weighing 300-350g were subjected to orthotopic intact liver allograft using a "sleeve" anastomosis for the hepatic artery. Total warm ischaemia ranged from 19 to 34 minutes and no storage was employed. Comparison was made with a group of control rats which were subjected to 25 minutes total inflow occlusion and regeneration was measured with tissue thymidine kinase (TK) and mitotic figures. Samples were taken at 1, 2, 4, 7, 10 and 20 days post-operatively. Plasma aspartate aminotransferase (AAT) and light microscopy were used to evaluate hepatocyte necrosis. There was a brief sharp increase in TK and AAT in the first 24 hours after sham operation but no appearance of mitotic figures. A similar but more prolonged increase in TK occurred in the arterialized transplant group with the highest levels recorded on day 4. The level remained significantly elevated above pre-operative until 10 days and declined within 20 days. Mitotic figures appeared at 2 days, reached significance at 7 and 10 days and had disappeared by 20 days. The pattern of changes was accentuated in animals in which the artery was not reanastomosed and the increases in TK and AAT were still significant at 20 days. Whilst similar degrees of peri-portal cellular infiltrate occurred in both groups of rats, bile duct proliferation was most obvious in non-arterialized animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1993

A case for changing the way schizophrenia is conceptualised, using a questionnaire to relatives.

In view of dissatisfaction among philosophers and many doctors with the DSM III criteria for schizophrenia a new conceptualization is needed. Recent research results showing the complex influences on the development and functions of the brain suggest that the primary problem is a reduced capacity for information processing and not the more obvious symptoms of acute episodes. An analysis of a questionnaire to relatives (members of the National Schizophrenia Fellowship) has been used to illustrate how data from relatives can provide useful indicators of some of the factors such as possible metabolic abnormalities and immune system deficiencies which may contribute to this problem. It is suggested that a broad data-base is needed to study such contributory factors and point the way to forms of treatment which might make lower levels of maintenance neuroleptic medication possible.

Antipsychotic Agents↗
PubMed1993

Liver regeneration after hepatic ischemia and reduced liver autotransplantation in the rat.

Current knowledge of liver regeneration after reduced liver transplantation is limited. Warm ischemia is one component of the reduced liver transplantation procedure that could have an impact on the regenerative response. To study this effect, we performed partial hepatectomy on male Long-Evans rats, with animals divided into four groups: group 1 underwent partial hepatectomy only; group 2 underwent partial hepatectomy and 40 min of ischemia; group 3 underwent partial hepatectomy, 40 min of ischemia and portocaval shunt surgery; and group 4 underwent partial hepatectomy and orthotopic autograft surgery. Group 5 consisted of sham-operated animals. Animals were killed 4, 24, 48, 72 and 96 hr after surgery. Thymidine kinase activity, mitotic index, a liver mass index and ornithine decarboxylase levels were used as parameters of liver regeneration. Aspartate transaminase was recorded. Maximal thymidine kinase and mitotic index were observed in group 1 animals at 24 hr. In groups 2, 3 and 4 maximal thymidine kinase activity and mitotic activity were observed 24 hr later at 48 hr. The magnitude of the peak response in these groups appeared to correlate with the duration of portal venous occlusion, with greatest increases occurring in those groups where portal stasis was most prolonged. The increase in liver mass for these groups was also delayed with respect to group 1 animals. The anticipated peak in ornithine decarboxylase levels was seen at 4 hr in group 1. The ornithine decarboxylase response in the other groups was disorganized, with delay of the recorded peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Identification of the loci of the collagen-associated Ehrlich chromogen in type I collagen confirms its role as a trivalent cross-link.

Collagenous peptides containing the Ehrlich chromogen (EC) were selectively isolated from a tryptic digest of bovine tendon by coupling to a diazotized polyacrylamide support. The isolated p-phenol-azo-EC peptides were purified and characterized by amino acid and sequence analyses. EC occurred in stoichiometric amounts in trimeric cross-linked chains originating from the known cross-link regions of type-I collagen. The major locus of the EC was alpha 2(I)Hyl-933 x alpha 1(I)Lys(Hyl)-9N x alpha 2(I)Lys(Hyl)-5N but it was also shown to occur at the loci alpha 1(I)Hyl-87 x alpha 1(I)Lys(Hyl)-16C x alpha 1(I)Lys(Hyl)-16C and alpha 1(I)Hyl-930 x alpha 1(I)Lys(Hyl)-9N x alpha 2(I)Lys(Hyl)-5N. After sequence analyses of the C-terminal helical cross-link region alpha 2(I)928-963, corrections are presented for residues 927, 930, 932 and 933 of the bovine alpha 2(I) chain. The collagen-associated EC is postulated to be a trisubstituted pyrrole formed by the reaction of the aldehyde form of a telopeptidyl lysine residue with a bifunctional keto amino cross-link. It is also proposed that when the telopeptidyl lysine residue is hydroxylated the above reaction will result in pyridinoline formation.

Amino Acid Sequence↗
PubMed1992

Effect of total hepatectomy on coagulation and glucose homeostasis in the pig.

It has been suggested recently that patients with fulminant liver failure should be prepared for transplantation by early hepatectomy, yet the acute effects of removal of the liver upon the coagulation profile and certain hormones are not known. This study was conducted on totally hepatectomized pigs that survived up to 27 hr. Measurements were made of serum insulin, plasma glucagon (IRG and GLI), glucose, catecholamines, and the coagulation profile. The increase in serum insulin was directly related to levels of plasma glucose--there was a 100-fold increase in animals with plasma glucose levels greater than 400 mg/100 ml and none when blood glucose was less than 100 mg/100 ml. Plasma glucagon showed a sharp transient increase within 1 hr of hepatectomy and a slow rise thereafter with levels apparently unrelated to serum insulin or plasma glucose. There was a transient increase in plasma adrenaline but a sharp continuous increase in plasma norepinephrine. No changes of note occurred in the coagulation profile--even levels of fibrinogen only declined by 20% in 27 hr. The study has shown that early total hepatectomy is safe as far as changes in coagulation are concerned but changes in serum insulin and especially plasma norepinephrine may be of more significance.

Animals↗
PubMed1992

How rapidly do hyperinsulinaemia and hyperglucagonaemia develop after portacaval shunting?

Elevation of serum insulin and plasma glucagon have been reported during and immediately after clinical and experimental liver transplantation and in patients with cirrhosis and surgically created or spontaneous portacaval shunts. There is controversy about the relative roles of portal diversion and impaired liver function in the genesis of these elevated levels of pancreatic hormones. End-to-side portacaval shunt was made in normal pigs which were fitted with catheters which allowed transhepatic sampling during and for 4 hr after the operation. Within 5 min of opening the shunt, there was a sixfold increase in portal venous insulin concentrations but hepatic clearance of insulin and the arterial concentration were unaltered. The increase in insulin was sustained for 2 hr. A twofold increase occurred within 1 hr in portal venous glucagon concentration which appeared to be predominantly of pancreatic origin and which continued for the 4 hr of the study. Hepatic glucose uptake did not occur after portacaval shunting despite levels of glucose elevated two-fold by iv infusion. There were no changes in aspartate aminotransferase, hepatic tissue energy charge, or total adenine nucleotides, suggesting that hepatic function was intact. It is concluded that portal diversion results in an increase in insulin and glucagon secretion and in the absence of hepatic uptake of glucose. This is a novel observation with relevance especially in liver transplantation when portal diversion for at least 1 hr forms part of the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Energy charge as an indication of liver viability. A comparison of changes in livers that remained intact with those subjected to autografting.

As efforts to assess the viability of liver grafts continue, the recent description of noninvasive measurement by fluorimetry or magnetic resonance spectrometry of adenine nucleotides has brought energy charge into focus again as an index of viability. Many previous studies have been conducted in human donor livers that have clinical relevance but which cannot be standardized, or in rats in which the hepatic artery is not anastomosed. In the present study, pig livers were definitively rendered ischemic for 1 or 2 hr. In one group the livers were then revascularized (intact) while in the other, the livers were removed during the final 20-30 min of the ischemic period and were subjected to autograft. There was a marked difference in survival between the intact and the autograft groups. One hour of ischemia in the intact group was associated with survival comparable to that of autograft controls (8-100 days); 2 hr of ischemia caused shortened survival, ranging from 2 to 18 days. In the recipients of autografts, survival after 1 hr of ischemia ranged from 3 to 16 days; after 2 hr of ischemia no autograft recipient survived overnight. The energy charge returned to the preoperative level after 2 hr of ischemia in both intact and autograft groups. The concentrations remained depressed after 2 hr of ischemia in autografted animals, thus being associated with survival. However, the patterns of total adenine nucleotide and adenosine triphosphate were not always similar to those of energy charge. The concentrations of aspartate aminotransferase were similarly elevated in all ischemic groups irrespective of duration or subsequent survival. There was, however, a close association between euglobulin lysis times (ELT) and survival. In the autograft recipients of livers subjected to 2 hr of ischemia that did not survive overnight the ELT remained significantly shortened. It is concluded that adenine nucleotide metabolism is important as an index of viability, but that concentrations of total and individual adenine nucleotides and the energy change all need to be computed. There does, however, appear to be an absolute relationship between survival and euglobulin lysis time that would be clinically useful in patients undergoing liver transplantation or hepatic vascular exclusion.

Adenine Nucleotides↗
PubMed1991

Transesophageal echocardiographic evaluation for mural thrombus following radiofrequency catheter ablation of accessory pathways.

BACKGROUND: Catheter ablation of accessory pathways (APs) provides a definitive therapy for patients with Wolff-Parkinson-White Syndrome. The reported incidence of thrombus formation on ablation-induced injuries with direct current shock varies from 0%-20% in animal studies. The purpose of this study was to determine the prevalence of mural thrombus following catheter ablation with radiofrequency current of accessory pathways in humans. METHODS AND RESULTS: Radiofrequency current (30-35 watts) was applied through a catheter electrode placed against the mitral or tricuspid annulus guided by catheter recordings of AP potentials. Transthoracic (TTE) and transesophageal echocardiography (TEE) were performed in 95 of 111 patients, at 18 +/- 6 hours following catheter ablation. After ablation, no thrombus was identified at or near the ablation site in any patient. Two out of 95 patients had a mural thrombus at a remote site that was detected by TEE but not by TTE. No new wall motion abnormality was detected in any patient. No significant regurgitant valvular lesion was found in any patient. CONCLUSION: Intracardiac thrombus was not identified at the site of catheter ablation, possibly owing to the small lesions produced by radiofrequency energy and high blood flow normally present in those areas. However, patients may be at small risk for mural thrombus at a remote site from prolonged placement of catheters.

Adult↗
PubMed1990

Transhepatic sampling during experimental porcine liver autotransplantation--its application to measurements of insulin, glucagon, and glucose.

Controversy still exists in the published literature about the need for administration of intravenous glucose during liver transplantation. The ability of the grafted liver to metabolize insulin and glucagon and the appropriateness of secretion of these hormones are addressed in the present study. Two groups of pigs received unstored liver autografts, one with free infusion of 10% glucose and the other with limited infusion of 2.5% glucose solution, while attempting to maintain plasma glucose levels less than 200 mg/100 ml. In these animals, irrespective of moderate or major hyperglycemia, serum insulin levels were appropriate for blood glucose concentrations. However, in both groups, plasma glucagon levels rose three- to fourfold more than preoperative values and were inappropriate. Although facilities for measurement of blood flow were not available, application of the technique of transhepatic sampling has revealed that hepatic handling of insulin seems to be unimpaired after autograft with limited ischemia. Pancreatic secretion of glucagon, however, appeared to increase during the period immediately after revascularization. It is suggested that transhepatic sampling methods may be used in experimental transplantation to elucidate the effects of storage for prolonged periods.

Animals↗