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THE ROLE OF PEROXISOMES IN INTERMEDIARY METABOLISM
CHANDOGA, J.
The dominant position among oxidoreduction processes
in peroxisomes is ascribed to catalase, a number of aerobic oxidases,
and Cu,Zn-superoxide dismutase. The peroxidase reaction of catalase
requires substrates for hydrogen donation, other than H[2]O[2],
e.g. alcohols, aldehydes, formic acid.
The peroxisomes contain an alternative system of beta-oxidation
of higher carboxylic acids which in some types of plant cells
is functionally very closely associated with the glyoxylate cycle.
Regarding the role of peroxisomes in the metabolism of carboxylic
acids, a very important finding has taken place, namely that besides
acyl-CoA synthetase which is specific for long chains, the peroxisomes
contain still another enzyme which allows the synthesis of CoA
esters of fatty acids with very long chains. It is assumed that
the entry of acyl-CoA esters or fatty acids into the peroxisomes
is performed by means of pores in mebranes or acyl-carnitine transferases.
Peroxisomes oxidize a very wide scale of substrates and contain
several types of acyl-CoA oxidases: palmitoyl-CoA oxidase, pristanoyl-CoA
oxidase, trihydroxy-coprostanoyl-CoA oxidase. The second and third
reactions of peroxisomal beta-oxidation are catalyzed by the so-called
three-functional enzyme, the activities of which are identical
to those of 2-enoyl-CoA hydratase, beta-hydroxyacyl-CoA dihydrogenase
and enoyl-CoA isomerase. The peroxisomes sufficiently oxidize
dicarboxylic acids with a higher number of carbons beginning with
the adipic acid. The peroxisomal system of beta-oxidation is utilized
in metabolism of prostaglandins, pristanic acid - being the product
of phytanic acid alpha-oxidation, and cholesterol.
Several enzymatic activities needed for the synthesis of cholesterol
partially take place in peroxisomes. The peroxisomes represent
a decisive compartment for the initial phases of synthesis of
plasmalogens. They contain the following enzymes: NAD[+]-glycerol-P-dehydrogenease,
dihydroxyacetone-3-P-acyl-transferase, alkyl-dihydroxyacetone-P
synthetase and acyl/alkyl-dihydroxyacetone-P reductase. The metabolism
of aminoacids takes place under the effect of peroxisomal enzymes
- oxidase of diaminoacids, D-asparate oxidase, oxidase of L-pipecolic
acid and alanine-glyoxylate aminotransferase. Only a few published
sources consider it obvious that liver peroxisomes participate
in degradation of spermine and spermidine. Polyamine oxidase oxidizes
spermine resulting in the origin of spermidine and 3-aminopropionaldehyde,
and spermidine is oxidized to putrescine and 3-aminopropionaldehyde.
Peroxisomes in many phylogenetically lower animal species enable
the break down of purine bases to urea and glyoxylic acid. In
phylogenetically higher primates and in man, the activities of
urate oxidase in peroxisomes are absent. (Fig. 14, Ref. 166.)
Key words: peroxisomes; catalase; superoxide dismutase; oxidases; dehydrogenases; carnitine transferases; beta-oxidation; alpha-oxidation; unsaturated fatty acids; dicarboxylic acids; cholesterol; bile acids; phospholipids; polyamine oxidation; aminotransferases; purine metabolism.
Bratisl Lek Listy 1995; 96: 465-486
TREATMENT OF VIRAL HEPATITIS
MIGUET, J.-PH., HRUSOVSKY, S.
Chronic forms
of viral B,C, and D hepatitis and fulminant hepatitis represent
a serious healthcare problem. The study deals with the changes
in the strategy in treating these diseases.
During the chronic active hepatitis caused by the B hepatitis
virus, the main aim of treatment is to cease multiplication of
viruses, eliminate the clinical symptoms, prevent the development
of cirrhosis, or the origin of hepatocellular carcinoma.
The authors analyze the possibilities of the application of corticosteroids,
viricidal drugs (vidarabin and interferons) and other medicaments
(acyclovir, zidovudin, duramin, gancyclovir, chinacrin, and others)
besides corticosteroids, interleukin 2 and tymozin from the group
of immunomodulators were tested. The testing included the factor
stimulating the colonies of granulocytes and myeloblasts and other
substances. The therapy of acute protracted B hepatitis by means
of interferon still requires controlled studies.
Superinfection by D virus in chronic carriers of HBsAG causes
chronic hepatitis which quickly leads to the development of cirrhosis.
The therapy on basis of alpha interferon decreases the RNA virus
D hepatitis serum level and leads to an improvement in the development
of chronic hepatitis in half of the patients.
Therapy of chronic C hepatitis on basis of corticosteroids is
ineffective, and can be dangerous. Acyclovir is proved to be ineffective
as well. The open study indicated certain positive results in
application of interferon.
The fulminant hepatitis can be defined as a development of encephalopathy
and a decrease of the prothrombin time to less than 50% in the
course of acute hepatitis. The break-point in the therapy of fulminant
hepatitis took place in association with the performance of the
transplantation of the liver. Impossibility to transplant the
liver means that the effect of therapy of fulminant hepatitis
is merely of supportive value. Majority of patients die due to
neurologic complications, namely unmanageable oedema of the brain.
But still, neither the antioedema therapy, e.g. on basis of manitol,
as well as by means of corticosteroids, hemodialysis, hemofiltration,
plasmapheresis and hemoperfusion, nor the treatment on basis of
E1 prostaglandine improved the survival of patients. (Tab.
2, Ref. 82.)
Key words: viral hepatitis; therapy; interferon; acyclovir; corticosteroids; transplantation of the liver; diagnosis.
Bratisl Lek Listy 1995; 96: 487-492
THE MEANING OF LAPAROSTOMY IN THE TREATMENT OF SEVERE HAEMORRHAGIC NECROTIC PANCREATITIS
BOBER, J., KRAUS, L., MATHERNYOVA, E., HARBULAK, P., CHYMCAK, I., ZAVACKY, P.
The authors present their experience with the therapy of severe necrotic pancreatits which was applied in the period from 1986 to 1993. Alcoholic etiology was stated in 52.56 % patients. The authors analyse in detail the cases treated with „open packing" laparostomy. They emphasise its advantages and advocate to its more frequent application. Laparostomy in the frame of complex therapy of acute pancreatits can contribute to mortality reduction. The mortality in the group of patients yielded 17.75 %. Complications and multiorgan failure with a high mortality rate and severe forms of necrotic pancreatitis still represent a sad component of abdominal surgery. (Tab. 6, Ref. 13.)
Key words: severe necrotic pancreatitis; laparostomy; „open packing".
Bratisl Lek Listy 1995; 96: 493-495
REASONS FOR CONVERSION OF LAPAROSCOPIC CHOLECYSTECTOMY TO LAPAROTOMY
LEHOTSKY, L., HUTAN, M.
Laparoscopic cholecystectomy (LCH) is a
surgical method which is minimally invasive thus enjoying an increasing
popularity among both patients among the patients surgeons.
Conversion of laparoscopic cholecystectomy is comprehended as
a retrieve to the classical surgical method based on laparotomy
in any phase of operation.
The study deals with reasons for conversion of the initial one
hundred LCH which were performed by 7 surgeons at the Department
of Surgery in Ruzinov Hospital in Bratislava during the period
from 27.11.1992 to 31.3.1994.
Out of one hundred cases, 5 LCH required conversion to open laparotomy
- 5 %. The most frequent rate of conversion is from 3 to 8 %.
Reasons for conversion in our patients include. Impossibility
to introduce safety the trocar with thevideocamera (1x), unclear
anatomic situation (1x), bleeding from the cystic artery (1x),
perforation of the gallbladder and subsequent leakage of bile
and stones in to the peritoneal cavity (1x), technical failure
(1x).
We cannot comprehend the conversion of LCH as a failure of the
operating surgeon. It insinuates that the surgeon is careful and
responsible for his patient. It is a sign of his good surgical
judgement. (Tab. 3, Ref. 20.)
Key words: laparoscopic cholecystectomy; reasons for conversion.
Bratisl Lek Listy 1995; 96: 496-498
"SHORT BYPASS" IN POPLITEAL ARTERY TREATMENT
PROCHOTSKY, A., SLEZAK, V., PRIECEL, L.
Authors present in case report a patient with occlusion of proximal section of popliteal artery which was resolved by the reconstructive vascular surgical procedure - short femoropopliteal bypass using autolognal saphenous vein as a graft. In discussion they deal with the problem of short bypass in traumatic injured lower extremities and also in atherosclerotic or other degenerative diseases of lower extremities arteries. On the account of particulars from literature they refer to the possibility of using various autolognal venous grafts and also artificial vascular protheses. They also deal with the adjuvant medical treatment from the point of view of prevention of a favourable closure of graft and its longterm patency. They presume that the short bypass is in indicated cases mainly in highly at risk patients fully justifiable. (Fig. 3, Ref. 13.)
Key words: short bypass; autolognal venous graft; vascular protheses.
Bratisl Lek Listy 1995; 96: 499-502