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Biomedical subjects

K Folkers

Publications and source records attributed to K Folkers.

At least 19 recordsLinked to original sources
PubMed1979

Structural requirements in positions 1, 2, 3, and 6 of the luteinizing hormone-releasing hormone (LH-RH) for antiovulatory activity.

Sixteen analogues of the luteinizing hormone-releasing hormone (LH-RH) were synthesized by the solid-phase method. In new and surprising relationships, it was found that the substitution of D-Trp into position 3 of [D- less than Glu1,D-Phe2,amino acid3,D-Phe6]-LH-RH significantly enhanced the antiovulatory potency, but substitution by Pro, N-Me-Phe,N-Me-Leu, or L-Trp reduced antiovulatory activity. The substitution of L- less than Glu in position 1 of [D-Phe2,Pro3,D-Phe6]-LH-RH by cyclohexylcarbonyl (Chc), benzoyl (Bz), Ac, Hyp, Ac-Met, hydrogen, Pro, and D- less than Glu residues, and the substitution of D-Phe in position 2 by D-Trp, D-His, D-Phg, and L-Phe residues resulted in analogues with no antiovulatory activity at 750 microgram/rat. Structural requirements for the design of inhibitors of higher potency have been discussed.

Amino Acid Sequence↗
PubMed1979

Clinical results of a cross-over treatment with pyridoxine and placebo of the carpal tunnel syndrome.

Clinical evaluation was made of cross-over treatments by pyridoxine and a placebo of patient 22 having the carpal tunnel syndrome. Extraordinary monitoring of the specific activities of the erythrocyte glutamic oxaloacetic transaminase proved a severe vitamin B6 deficiency, which was partially corrected by the Recommended Dietary Allowance of 2 mg, and completely corrected by 100 mg. The severity of the syndrome diminished on the Recommended Dietary Allowances and the patient was asymptomatic at the higher dosage. On placebo, both the vitamin B6 deficiency and syndrome reappeared. Retreatment with 100 mg again corrected both the deficiency and syndrome. Measurements (total n = 19) of flexion of proximal interphalangeal joints of the index fingers by a goniometer, and of pinch by the Preston gauge revealed objective normalization. Scores of 17 symptoms revealed reductions at both the 2- (P less than 0.01) and 100-mg (P less than 0.001) dosages. Conduction through the carpal tunnels had improved by electromyography. These and previous data on a total of 22 patients showed the concomitant presence of a deficiency of vitamin B6 and the carpal tunnel syndrome; a causal relationship is apparent.

Adult↗
PubMed1979

Synthesis of substance P analogs and agonistic and antagonistic activities.

Fourteen analogs of substances P (SP), six previously synthesized by a solution method and eight newly synthesized by a solid-phase technique, have been tested for agonistic and antagonistic activities utilizing the isolated guinea pig ileum. The primary objective is to achieve effective inhibitors of SP. These analogs had agonistic activities ranging from negligible to that equivalent to SP. Six of the fourteen analogs had some degree of antagonistic activity [D-Leu8, D-Phe9]-SP is an analog which constitutes a lead to new substitutions, because it had antagonistic activity, but only negligible agonistic activity. One concept for effective antagonistic activity requires negligible or no agonistic activity.

Animals↗
PubMed1979

Prevention by coenzyme Q10 of the electrocardiographic changes induced by adriamycin in rats.

The administration of adriamycin (ADM) to rats has consistently caused a widening of the QRS complex of the electrocardiogram. When coenzyme Q10 was also administered, beginning two days before ADM, this widening of the QRS complex and the elongation of the Q-T interval were reduced or totally prevented, depending upon conditions. ADM alone or with coenzyme Q10 did not alter the P-R interval. Some control by coenzyme Q10 of the cardiotoxicity of adriamycin in cancer patients is promising.

Animals↗
PubMed1979

Study of the combined and separate administration of doxorubicin and coenzyme Q10 on mouse cardiac enzymes.

Administration of an acutely toxic dose of doxorubicin to mice did not increase, but rather decreased the percent deficiency of coenzyme Q10 (CoQ10) as calculated according to the coenzyme-apoenzyme system principle. The date indicate that doxorubicin may occupy CoQ10-empty receptors on the apoenzyme, with or without some destruction of enzyme-menbrane structure close to the receptor. Data from mice receiving both CoQ10 and doxorubicin indicated that CoQ10 may protect against doxorubicin. CoQ10 alone corrected the pre-existing deficiency found in control mice.

Animals↗
PubMed1978

Inhibitory analogues of the luteinizing hormone-releasing hormone having D-aromatic residues in positions 2 and 6 and variation in position 3.

A single sc injection of 750 microgram/rat of [D-Phe2,Pro3,D-Phe6]-LH-RH on proestrus completely inhibited ovulation in 4-day cycling rats. Ovulation was inhibited partially at 375 microgram/rat. At the 720 microgram/rat dosage, analogues of LH-RH with D-Phe in positions 2 and 6, and with Sar, Arg, or Hyp in position 3, resulted in partial inhibitors and an inactive analogue with Thr substitution. In the same assay, analogues with D-Phe in position 2 and D-Trp in position 6 were partial inhibitors when D-Phe, Met, or Val were in position 3 and inactive with Ile substitution.

Animals↗
PubMed1978

Rescue by coenzyme Q10 from electrocardiographic abnormalities caused by the toxicity of adriamycin in the rat.

The administration of adriamycin to rates increased (P less than 0.01) the interval, measured in msec, of the electrocardiographic QRS traces in rats, and the magnitude of the increase was ca. 50%. The administration of coenzyme Q10 to such adriamycin-treated rats allowed "rescue" or restoration of a normal QRS complex after 7 days of administration of coenzyme Q10. The QRS complex then remained normalized during the subsequent period of 21-30 days, by which time the cumulative dose of adriamycin had reached 24 mg/kg. Also, the QRS interval was lower (P less than 0.01) on day 33 than it was for rats treated to the same day with adriamycin alone. Coenzyme Q10 offers promise of rescue from at least some of the cardiotoxicity occurring in adriamycin-treated cancer patients, probably by a similar mechanism to that of the clinical rescue from toxicity of methotrexate by a cofactor of folic acid (citrovorum factor).

Animals↗
PubMed1978

Competitive inhibition of benzodiazepine binding by fractions from porcine brain.

Fractions of porcine cerebral cortex extract separated by molecular weight on a Sephadex G-75 column were tested for their activities and potencies to inhibit [3H]benzodiazepine binding to rat brain homogenates. The fractions spanned molecular weights from 500 to 100,000. A potent inhibitor (benzodiazepine-competitive factor I, BCF-I) was discovered in the fraction containing substances with molecular weights from 40,000 to 70,000. Equilibrium binding studies indicated that BCF-I was a competitive inhibitor, making it a candidate as a benzodiazepine endogenous factor or profactor. BCF-I was heat stable, but trypsin digestion destroyed its activity. Another inhibitory fraction (BCF-II) was 1/5th as active as BCF-I and contained substances with molecular weights from 1000 to 2000.

Animals↗
PubMed1978

Biochemical evidence for a deficiency of vitamin B6 in the carpal tunnel syndrome based on a crossover clinical study.

In a patient with severe carpal tunnel syndrome and a significant deficiency of vitamin B(6), the evidence for the deficiency was an extraordinarily low basal specific activity of the glutamic-oxaloacetic transminase of the erythrocytes (EGOT). This enzyme was also deficient in pyridoxal phosphate. The patient was treated with the recommended dietary allowance of pyridoxine, 2 mg/day, for 11 weeks, then 100 mg/day for 12 weeks, a placebo for 9 weeks, and again pyridoxine at 100 mg/day for 11 weeks. Sixty-one monitorial assays of EGOT over 48 weeks supported the following interpretations. (i) His diet permitted the development of a debilitating carpal tunnel syndrome. (ii) Treatment with pyridoxine at 2 mg/day reduced the deficiency of EGOT activity from about 70% to 50%, maintained a deficiency of pyridoxal phosphate, and relieved but allowed a marginal syndrome. (iii) Treatment at 100 mg/day for 12 weeks nearly achieved a "ceiling" level of EGOT and eliminated the deficiency of pyridoxal phosphate. (iv) After placebo for 7 weeks, the deficiencies of EGOT activity and pyridoxal phosphate reappeared, and clinical symptoms become worse. (v) Retreatment at 100 mg/day reestablished a "ceiling" EGOT, with no deficiency of pyridoxal phosphate, and the patient was asymptomatic. These data also support the concept that a deficiency of vitamin B(6) is significant in the etiology of the carpal tunnel syndrome. Mechanistically, a state of deficiency of the coenzyme seems to lower the level of the apoenzyme; a state of no deficiency of the coenzyme regulates a ceiling level of the transaminase. The latter state is presumably desired for health.

Apoenzymes↗