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Biomedical subjects

K Folkers

Publications and source records attributed to K Folkers.

At least 91 records · Page 5Linked to original sources
PubMed1988

Coenzyme Q10 content in different parts of the normal human heart.

Coenzyme Q10 (CoQ10) and citrate synthase (CS) activities were analysed in the myocardium of brain-dead organ donors (14-40 years). Different parts of the heart were studied: right and left auricular appendage, right and left atrium, right ventricle (septum and free wall) and left ventricle (septum, free wall, and papillary muscle). Freeze-dried, dissected myocardial samples were analysed for CoQ10 content by HPLC and CS activity by fluorometric technique. CoQ10 content in the normal human myocardium was lowest in auricular appendages and atria (0.25 +/- 0.06 mg X g-1 dry muscle), intermediate in right ventricle (0.37 +/- 0.05 mg X g-1 dm) and highest in left ventricle (0.42 +/- 0.07 mg X g-1 dm). CS activity showed the same relationship between these locations as CoQ10. The results suggest that there exist differences in CoQ10 content between different parts of the normal human myocardium. These differences were closely related to the differences in CS activity between corresponding parts. The differences between different parts of the heart may be related to divergent work demand, and the constant relationship between CS and CoQ10 may be related to their coupling to the mitochondrial oxidative metabolism.

Adult↗
PubMed1988

Significance of biological parameters of human blood levels of CoQ10.

Ninety-one men and 143 women who were so-called normal subjects were tested for cardiac performance at rest and their blood levels of co-enzyme Q10 (CoQ10) were determined. In males, a negative relationship between progression of age and cardiac performance, and a positive relationship between progression of age and blood levels of CoQ10 were revealed. In females, a positive relationship between age and blood levels of CoQ10 was found. The mean CoQ10 blood level for both sexes was the same (0.79 +/- 0.20 micrograms/ml for males and 0.79 +/- 0.23 for females). Cardiac performance declines with age in the male population. A decreased biosynthesis and/or incorporation of CoQ10 into mitochondrial structures of muscle cells may occur with age in a normal population.

Adult↗
PubMed1988

A superior analysis of coenzyme Q10 in blood of humans, rabbits and rats for research.

The quantitative analysis of coenzyme Q10 (CoQ10) in samples of whole human blood has been refined to allow a 2- to 3-fold increase in the number of analyses per day, and reduction of cost to approximately 15% of the previous cost. The method is simple yet maintains reliability. The standard error was 0.2% (n = 6). The variation in blood levels of CoQ10 for human subjects for each of three months was approximately 5% in comparison with the control value (n = 5). For 30 human males, of 18-50 years (26 +/- 6) in age, and for 30 human females, of 18-50 years (26 +/- 9), the mean blood level of CoQ10 was 0.71 +/- 0.13 microgram/ml and 0.70 +/- 0.18 microgram/ml respectively. The mean blood levels of CoQ10 of rabbits (n = 28) was 0.29 +/- 0.07 micrograms/ml, and that for rats (n = 29) was 0.23 +/- 0.03 micrograms/ml.

Adult↗
PubMed1988

A modified determination of coenzyme Q10 in human blood and CoQ10 blood levels in diverse patients with allergies.

Two situations required a modified determination of coenzyme Q10 (CoQ10) in human blood and organ tissue. Blood from patients with AIDS and cancer raised apprehensions about safety to an analyst, and the number of specimens for analysis is increasing enormously. A modified determination replaces silica gel-TLC with disposable Florisil columns, and steps were simplified to allow more analyses per unit time. Data from the modified determination are quantitatively compatible with data from older and tedious procedures. This determination was used for blood from 36 diverse patients with allergies. The mean CoQ10 blood level of these patients is not different from the mean level of so-called normal individuals, but approximately 40% (14/36) of these allergic patients had levels up to 0.65 micrograms/ml, which is the level of dying class IV cardiac patients. The biosynthesis of CoQ10 in human tissues is a complex process that requires several vitamins and micronutrients, so that countless vitamin-unsupplemented Americans may be deficient in CoQ10. The relationship of allergies to autoimmune mechanisms and immunity, and the established relationship of CoQ10 to immune states, may be a rationale for therapeutic trials of administering CoQ10 to patients with allergies who have low CoQ10 blood levels and are very likely deficient.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Design, synthesis and bioassays of antagonists of LHRH which have high antiovulatory activity and release negligible histamine.

Potent antagonists of the luteinizing hormone releasing hormone have been achieved which release negligible histamine. [N-Ac-D-2-Nal1, D-pClPhe2, D-3-Pal3, NicLys5, D-NicLys6, ILys8, D-Ala10]-LHRH showed 100%AOA/1 microgram and 36%/0. 5 micrograms; ED50 greater than 300. [N-Ac-D-2-Nal1,D-pClPhe2,D-3-Pal3, PicLys5, D-PicLys6, ILys8, D-Ala10]-LHRH showed 100% AOA/0.5 micrograms and 40%/0.25 micrograms; ED50, 93 +/- 11, and is the most potent of 52 new peptides. These antagonists feature designs with weakly basic acylated D-Lys6, notably D-NicLys6 and D-PicLys6 and alkylated Lys8 or Orn8, e.g., ILys8 and IOrn8, and NicLys5 and PicLys5. Concepts included balanced overall basicity, superiority of ILys8 and IOrn8 which are sequence dependent and sensitivity of positions 5 and 6 for potency.

Animals↗
PubMed1986

The toxicity of tetrahydrobiopterin: acute and subchronic studies in mice.

Tetrahydrobiopterin (BH4) is presently being employed in clinical trials for the therapy of various neurological disorders. The toxicity of BH4 in mice was analyzed by acute and subchronic intraperitoneal and acute oral survival studies. Organ weight analysis and histopathology were performed after acute and subchronic i.p. administration. The effect of probenecid on BH4 toxicity was also tested. An LD50 of approximately 260 mg/kg was obtained from acute (14-day) intraperitoneal survival studies. A dose-dependent increase in kidney weights and histopathologic evidence of acute toxic tubular necrosis were noted in acute i.p. studies. Acute oral administration of up to 1318 mg/kg BH4 did not cause any significant morbidity or mortality, nor did subchronic (92-day) i.p. administration of 10 or 50 mg/kg BH4. Probenecid pretreatment did not decrease the toxicity of BH4. The importance of further evaluation of the potential toxicity of tetrahydrobiopterin in clinical utilization is emphasized.

Administration, Oral↗
PubMed1986

Increased potency of antagonists of the luteinizing hormone releasing hormone which have D-3-Pal in position 6.

Ever increasing potency is an international goal for antagonists of the luteinizing hormone releasing hormone (LHRH). [N-Ac-D-2-Nal1,D-pClPhe2, D-3-Pal3,Ser4,Arg5,D-3-Pal6,Leu7,Arg8,Pro9,D- Ala10]-NH2 caused 60%/125 ng inhibition of ovulation in the rat, and appears to be the most potent antagonist yet described. Strategy of design was the replacement of D-Arg6 with D-3-Pal6 and of Tyr5 with Arg5. Replacing Arg5 with His5 reduced activity by 50% at 250 ng. Both the Arg5 and His5 analogs showed 100% inhibition of ovulation at 0.5 microgram. Of ten pairs of analogs with D-3-Pal6 and D-Arg6, 3/10 with D-3-Pal6 were more potent than those with D-Arg6. Histamine release was less for the D-3-Pal6 peptides of three pairs.

Alanine↗
PubMed1986

Decapeptides as effective agonists from L-amino acids biologically equivalent to the luteinizing hormone-releasing hormone.

Apparently, no agonist has been found that is comparable in potency to the luteinizing hormone-releasing hormone (LHRH) for release of LH and follicle-stimulating hormone (FSH) without substitutions with unnatural or D forms of natural amino acids. Of 139 known "agonist analogs" of LHRH, two were active in the range of 65%. The four LHRHs known to occur in nature involve a total of six amino acids (Tyr, His, Leu, Trp, Arg, Gln) in positions 5, 7, and 8. There are 16 possible peptides with these six amino acids in positions 5, 7, and 8, of which 4 are the known LHRHs, and 2 more were synthesized. We have synthesized the 10 new peptides and assayed 11 in vivo and in vitro, and we found not only 1 but a total of 5 that have activity equivalent to or greater than that of LHRH for the release of LH and/or FSH under at least one assay condition. These five are as follows: [His5,Trp7,Gln8]LHRH; [His5,Trp7,Leu8]LHRH; [His5,Trp7]LHRH; [Trp7]LHRH; [His5]LHRH. Two of these five agonists variably released relatively more FSH than LH. One or more of these five agonists may occur in nature and one may be follicle-stimulating hormone-releasing hormone. The two peptides with Gln8 and Leu8, if occurring in nature, may have different receptors according to radioreceptor assays and to the ratio of LH/FSH release in vivo. These structures are a basis for the design of antagonists without Arg8 toward avoiding histamine release. Complete inhibition of LH and FSH release in vivo may be induced by joint use of Arg8 and Gln8 or Leu8 antagonists. These potent agonists, related to LHRH, may be therapeutically useful in disorders of reproduction, the central nervous system, and for the control of hormone-dependent carcinomas.

Amino Acid Sequence↗
PubMed1986

Design and synthesis of antagonists of substance P.

Synthesis and bioassay of about 65 analogs of substance P (SP) over five years yielded the antagonist [D-Arg1,D-Trp7,9,Leu11]-SP, which was named Spantide, and which was used by many investigators as a "tool". Spantide served as a reference antagonist for the design of 47 new peptides toward the goal of more potent inhibitors. Designs emphasized analogs with D-Trp7, D-Trp9, D-Trp10, D-pClPhe10, Nle11, Leu11, Ile11 and Met11, etc. Twenty-one/47 antagonists were superior in potency to that of Spantide, the best was [D-Arg1,D-Na1(5), D-Trp7,9,Nle11]-SP which required a 255-fold increase in SP concentration to give 50% of the maximum response at a concentration of 10(-5)M of the antagonist; this potency is ca. 5 times that of Spantide. For certain, but not all pairs of undecapeptides and truncated analogs, the undecapeptides may be significantly more potent than the truncated counterparts.

Amino Acid Sequence↗
PubMed1985

Behavioural and antinociceptive effects of intrathecally injected substance P analogues in mice.

The antinociceptive effects and antagonism of substance P (SP)-induced behaviour were examined after intrathecal injections in mice. When coadministered with SP, the SP analogues attenuated the SP-induced behaviour to various extents with [D-Arg1,D-Pro2,4,D-PHe7,D-His9]SP as the most potent antagonist. Physalaemin and eledoisin brought about a SP-like behavioural response. [D-Arg1,D-Trp7,9,Leu11]SP inhibited the response to eledoisin but not that to physalaemin. The SP analogues substituted with D-Trp7,9 and with Leu or Val in position 11 produced the strongest antinociceptive effects. Pretreatment with naloxone (5 mg/kg, i.p.) abolished the antinociceptive effects of [D-Trp7,9,Leu11]SP, implying that opiate receptors in the spinal cord mediate at least in part the antinociceptive effects. Animals under pentobarbital anesthesia showed a potentiated antinociceptive effect in the tail-flick test. In conclusion, we found that the SP analogues tested exerted varying degrees of antinociception, and that this was probably at least in part mediated by activation of spinal opiate receptors, whereas the behavioural antagonism was probably due to the blockade of spinal SP receptors.

Analgesics↗
PubMed1985

Response of patients in classes III and IV of cardiomyopathy to therapy in a blind and crossover trial with coenzyme Q10.

Coenzyme Q10 (CoQ10), a biochemically established redox component of respiration including the coupled mechanisms of electron transfer and oxidative phosphorylation, is naturally present in the human myocardium. A double-blind and double-crossover trial has been conducted by administering CoQ10 and a matching placebo orally to two groups of patients having class III or IV cardiomyopathy (classification according to criteria of the New York Heart Association). Group A received CoQ10 and then placebo; group B received placebo and then CoQ10. Blood levels of CoQ10 and cardiac function were determined at 0 and 4 weeks (control stabilization period) and at 16 and 28 weeks (after the 12-week CoQ/placebo-treatment periods). For group A, significant increases in CoQ10 blood levels and cardiac function occurred during CoQ10 treatment and then decreased during crossover to placebo. For group B, there was no change in CoQ10 blood levels and cardiac function during placebo treatment, but increases in both parameters occurred in crossover to CoQ10. These patients, steadily worsening and expected to die within 2 years under conventional therapy, generally showed an extraordinary clinical improvement, indicating that CoQ10 therapy might extend the lives of such patients. This improvement could be due to correction of a myocardial deficiency of CoQ10 and to enhanced synthesis of CoQ10-requiring enzymes.

Adult↗
PubMed1985

Biochemical rationale and the cardiac response of patients with muscle disease to therapy with coenzyme Q10.

Cardiac disease is commonly associated with virtually every form of muscular dystrophy and myopathy. A double-blind and open crossover trial on the oral administration of coenzyme Q10 (CoQ10) to 12 patients with progressive muscular dystrophies and neurogenic atrophies was conducted. These diseases included the Duchenne, Becker, and limb-girdle dystrophies, myotonic dystrophy, Charcot-Marie-Tooth disease, and Welander disease. The impaired cardiac function was noninvasively and extensively monitored by impedance cardiography. Solely by significant change or no change in stroke volume and cardiac output, all 8 patients on blind CoQ10 and all 4 on blind placebo were correctly assigned (P less than 0.003). After the limited 3-month trial, improved physical well-being was observed for 4/8 treated patients and for 0/4 placebo patients; of the latter, 3/4 improved on CoQ10; 2/8 patients resigned before crossover; 5/6 on CoQ10 in crossover maintained improved cardiac function; 1/6 crossed over from CoQ10 to placebo relapsed. The rationale of this trial was based on known mitochondrial myopathies, which involve respiratory enzymes, the known presence of CoQ10 in respiration, and prior clinical data on CoQ10 and dystrophy. These results indicate that the impaired myocardial function of such patients with muscular disease may have some association with impaired function of skeletal muscle, both of which may be improved by CoQ10 therapy. The cardiac improvement was definitely positive. The improvement in well-being was subjective, but probably real. Likely, CoQ10 does not alter genetic defects but can benefit the sequelae of mitochondrial impairment from such defects. CoQ10 is the only known substance that offers a safe and improved quality of life for such patients having muscle disease, and it is based on intrinsic bioenergetics.

Administration, Oral↗
PubMed1985

Biochemical rationale and myocardial tissue data on the effective therapy of cardiomyopathy with coenzyme Q10.

The tissue levels of coenzyme Q10 (CoQ10) in endomyocardial biopsy samples and blood from 43 patients with cardiomyopathy were determined by steps of extraction, purification, and HPLC. The biopsy samples were obtained from the patients after a routine heart catheterization. Six patients were of class I, 18 of class II, 11 of class III, and 8 of class IV (classified according to guidelines of the New York Heart Association). True control biopsies of healthy hearts are not available for ethical reasons, but the data of the four classes by severity of disease may be justifiably compared. Patients of class IV had lower (P less than 0.01) levels of CoQ10 than those of class I. Patients of classes III and IV had a lower (P less than 0.0001) level than those of classes I and II. Biopsy samples were obtained from five patients after treatment with CoQ10 for 2-8 months. The increases of CoQ10 levels ranged from 20% to 85%; the mean value was higher (P less than 0.02) than before treatment. Blood deficiencies also increase with severity of disease, but not as markedly as for the biopsies. These data reveal a myocardial deficiency of CoQ10, which is higher with increasing severity of disease and is reduced by therapy. This biochemistry correlates with the effective treatment of cardiomyopathy with CoQ10.

Biopsy↗
PubMed1985

Research on coenzyme Q10 in clinical medicine and in immunomodulation.

Coenzyme Q10 (CoQ10) is a redox component in the respiratory chain. CoQ10 is necessary for human life to exist; and a deficiency can be contributory to ill health and disease. A deficiency of CoQ10 in myocardial disease has been found and controlled therapeutic trials have established CoQ10 as a major advance in the therapy of resistant myocardial failure. The cardiotoxicity of adriamycin, used in treatment modalities of cancer, is significantly reduced by CoQ10, apparently because the side-effects of adriamycin include inhibition of mitochondrial CoQ10 enzymes. Models of the immune system including phagocytic rate, circulating antibody level, neoplasia, viral and parasitic infections were used to demonstrate that CoQ10 is an immunomodulating agent. It was concluded that CoQ10, at the mitochondrial level, is essential for the optimal function of the immune system.

Aged↗
PubMed1985

Effective treatment with coenzyme Q10 of patients with chronic myocardial disease.

Nineteen patients with chronic myocardial disease (NYHA Classes III and IV) were given Coenzyme Q10 in a controlled double-blind cross-over study. All had either low or borderline levels of CoQ10 in their blood, and showed a significant change into the normal range with oral CoQ10 replacement. Eighteen patients reported improvement in activity tolerance with replacement therapy. Combined clinical observations, stroke volume measured by impedance cardiography, and ejection fractions calculated from systolic time intervals, all showed significant improvement in parallel with CoQ10 administration. This application of the principles of bioenergetics introduces a promising new dimension to the study and treatment of the complex problem of myocardial failure.

Cardiomyopathies↗
PubMed1985

Long-term coenzyme Q10 therapy: a major advance in the management of resistant myocardial failure.

Coenzyme Q10 (CoQ10) treatment, orally administered as 100 mg daily dose, was initiated in a series of patients with advanced heart failure in an open, controlled design. They were all showing an insufficient response to classical therapy with diuretics and digitalis. Twelve patients with various causes of heart failure, classified clinically by echocardiography (ECHO), (12/12), and heart catheterization with endomyocardial biopsy, (10/12), were followed prospectively for a mean period of seven months. Serial assessments: Clinical examination (with questionnaire), ECG, chest X-ray, ECHO, systolic time intervals (STI) and blood levels of CoQ10 were performed. With a mean latency period of 30 days, eight out of 12 patients (67%) showed definite clinical improvement. Subjectively, the patients felt less tired, their general activity tolerance increased and dyspnoea at rest disappeared. There were obvious signs of decreased right-sided stasis (hepatic congestion). The heart rate fell significantly, and the heart volume (chest X-ray) decreased in the eight responders (although n.s.). A significant reduction in the left atrial size (ECHO) was registered, suggesting a reduced preload of the left ventricle, Furthermore, a significant decline in the PEP/LVET ratio (STI) was indicative of an improved myocardial performance. Preliminary CoQ10 withdrawal results showed severe clinical relapse with subsequent improvement on CoQ10 reinstatement, supporting the interpretation that treatment of these patients corrected a myocardial deficiency of CoQ10 and increased contractility. Hence CoQ10 appears to be an effective therapeutic agent in advanced cases of heart failure. This is an attractive circumvention of the traditional principles of therapy: supporting the myocardium directly by ameliorating a supposed underlying mitochondrial dysfunction (exhausted bioenergetics).

Adolescent↗