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Biomedical subjects

K Peters

Publications and source records attributed to K Peters.

At least 253 records · Page 14Linked to original sources
PubMed1984

Mild analgesics and the accident and emergency department--cost and safety more important than potency?

A prospective controlled trial involving over 1000 patients did not reveal any difference between four drugs commonly used in accident and emergency departments for the relief of mild to moderate pain. There were no significant variations in therapeutic effect, side-effects or patient compliance. When considering the supply of analgesics which may be no more potent than those available without prescription from retail chemists, cost and safety are more important than analgesic effect. By restricting the choice of analgesics available, the accident and emergency department should be able to increase awareness among its staff of the actions and side-effects of a small number of prescribed drugs and to contain costs.

Acetaminophen↗
PubMed1984

[Thermitase--a thermostable serine protease. VI. Kinetic and fluorescence studies on the interaction of the enzymes with dansylated peptide chloromethylketones].

The modification of thermitase with dansylated peptide chloromethyl ketones Dns-Alan-PheCH2Cl (n = 1 to 4) was investigated by means of kinetic and fluorescence methods. Furthermore the influence of dimethyl formamide and dimethyl sulfoxide on the enzyme activity is reported. The synthesis of the Dns-substituted chloromethyl ketones acting as irreversible inhibitors was started from the analogous Z-compounds. The substances Dns-Alan-PheCH2-Cl with n = 1, 2, and 3 have lower inhibition effects than the sequence homologous Z-protected peptide chloromethyl ketones. The fluorescence measurements showed that the dansyl group forms hydrophobic interactions with the enzyme and takes part in energy transfer processes particularly in the case of thermitase labelled with Dns-Ala2-PheCH2Cl. From the kinetic data of the Dns- and Z-protected inhibitors it is concluded that thermitase presents five subsites at the S-site of its active center. This confirms our earlier assumption that the topology of the active center of thermitase is comparable with that of subtilisin BPN'.

Actinomycetales↗
PubMed1982

Effect of intramuscular vitamin E on frequency and severity of retrolental fibroplasia. A controlled trial.

126 appropriate-for-gestational age neonates born in hospital with birth-weights of 750 g-1500 g were prospectively studied in a randomised trial to determine the effect of intramuscular vitamin E on the frequency and severity of retrolental fibroplasia (RLF). In the 99 who lived for more than one month the frequency of active RLF in the vitamin E and control groups in the nursery (18.8% vs 23.5%) and at discharge (8.3% vs 19.6% was not significantly different. Vitamin E had significantly reduced the severity of RLF at follow-up eye examination 6-33 months after discharge (p less than 0.01). 3 control infants (760 g, 780 g, 1020 g) were blind in both eyes (grade V cicatricial RLF), whereas the most severe grade of disease in the vitamin E infants was grade II cicatrix. Infants in whom RLF developed were gestationally younger (p = 0.005), required a longer period of mechanical ventilation (p = 0.035), had a greater exposure to oxygen (p = 0.03), and had a greater number of arterial PO2 values between 75 and 99 mm Hg (p = 0.004). Early administration of vitamin E, while not affecting the frequency of RLF, will significantly reduce its severity and subsequent eye damage, and such treatment is recommended for all low-birth-weight infants of less than 1250 g who require supplementary oxygen.

Acute Disease↗
PubMed1981

Estimated cerebral blood flow in term infants with hypoxic-ischemic encephalopathy.

Estimated cerebral blood flow (eCBF) was measured sequentially in seven term infants with evidence of hypoxic-ischemic encephalopathy (HIE) and compared with that of normal-term infants. The eCBF was determined by a noninvasive method involving brief bilateral jugular venous occlusion with simultaneous measurement of occipitofrontal circumference. There was a significant decrease in eCBF on day 2 (30 +/- 4 ml/min/100 g brain weight) and on day 4 (36 +/- 5 ml/min/100 g brain weight) compared with control values (56 +/- 4 ml/min/100 g brain weight; 54 +/- 4 ml/min/100 g brain weight) (P less than 0.01). The alveolar CO2 was significantly lower on days 2 and 4 in the HIE group (P less than 0.001), and these values increased to control values by day 6. There was no significant correlation between estimated cerebral blood flow and alveolar CO2 in infants with HIE. We conclude that term infants with evidence of hypoxic-ischemic encephalopathy demonstrate lowered eCBF in the first 4 days of life.

Asphyxia Neonatorum↗
PubMed1981

[Variability of the dose effect in the radio-biologic experimentation on animals. Second communication: influence of breed, sex, age as well as of infections on death rates and LD 50 values (author's transl)].

As already demonstrated for Wistar rats, the radioresistance of Siv-50 male and female rats increases continually during their first months of life. Furthermore, males show a higher radioresistance than females during this period. The authors show with the same animals that a very radiosensitive rat strain can become a highly radioresistant strain after 2 1/2 years. After whole-body irradiation with 800--900 R, the increase of resistance of 85 days old males was between 62% and 68%. As a cause of this resistance increase, a mixed infection with Bordetella bronchiseptica and other germs is discussed. On the basis of literature, the authors discuss the occurrence of radioresistance increases after immunization or preconditioning with various bacterial vaccines and bacterial endotoxins.

Age Factors↗
PubMed1981

[Variability of the dose effect in the radio-biologic experimentation on animals. Third communication: Influence of breed, sex, age as well as radiation dose on body weight and survival time in days after whole-body irradiation of Wistar and Siv-50 rats (author's transl)].

After a whole-body irradiation of Wistar and Siv-50 rat males and females with 600 to 900 R, the survival times and the development of weight of the irradiated animals were determined and compared. The development of body weight was influenced by the dose administered as well as by age, sex and breed of the animals. Furthermore, the weight curves showed also characteristic analogies. During a period of 30 days after the irradiation, there are generally two phases with a considerable weight loss which are both accompanied by a reduced absorption of drinking-water and the appearance of a gastrointestinal and hemopoietic irradiation damage as well as the resulting activity increase of the pituitary gland and the cortex of the suprarenal gland. The weight recovery occurring after sublethal radiation doses is also influenced by the administered dose and the age of the animals. The dropping weight curves of dying animals are equally dependent on the administered dose. With regard to the survival time in days in dependence upon the administered dose and the age of the animals, the authors proved that the survival time of the finally dying animals becomes longer as their radioresistance increases. During the last phase of the 30 days' experimentation, females show a markedly increased death rate whereas males seem to have continually better survival chances when they are still alive at the last phase.

Age Factors↗
PubMed1980

[The effect of sulfur compounds (N-acetylhomocysteine-thiolactone and penicillamine) on liver collagen metabolism in chronic thioacetamide poisoning].

The influence of N-acetyl-homocysteine-thiolactone (AHCT) and penicillamine on experimental thioacetamide (TAA)-induced liver fibrosis was investigated. TAA causes an increase in liver collagen content, which can partly be prevented by penicillamine and AHCT. This prevention is most effective, when the TAA-intoxication started earlier than the therapy with these two substances. The therapeutic effect of penicillamine is achieved by an inhibition of collagen biosynthesis and cross-linking (with an increase in the easily soluble collagen fractions). In the case of AHCT the inhibition of pathological collagen synthesis in experimental liver fibrosis cannot be explained by disturbed collagen cross-linking or increased collagen solubility. Whether collagen synthesis is inhibited and/or other influences of AHCT are present has still to be analyzed.

Acetamides↗
PubMed1978

Picosecond dynamics of primary electron-transfer processes in bacterial photosynthesis.

The primary electron transfer processes in Rhodopseudomonas sphaeroides R-26 were studied as a function of temperature by means of picosecond spectroscopy. The first chemical step of the bacterial photosynthesis involves an electron transfer from the excited state of a bacteriochlorophyll a dimer, (BChl)2, to a bacteriopheophytin (BPh) to form the radical ion pair (BChl)2+. BPh-.. The upper limit for the formation time of this ion-pair was found to be 10 ps, at temperatures in the range 300-4.2 degree K. Similarly, the second chemical step, involving electron transfer from BPh-. to an ubiquinone-iron complex (QFe), was found to have a lifetime of approximately 150 ps, also independent of temperature in the same range. We interpret the absence of temperature dependence as indicating that process 2 proceeds via a tunneling mechanism. Utilizing our results in conjunction with electron tunneling theories, we calculate the distance between BPh-. and Q(Fe) to be 9--13 A. Our results also imply a closer proximity between (BChl)2 and BPh.

Oxidation-Reduction↗
PubMed1977

Primary photochemical event in vision: proton translocation.

Picosecond studies of rhodopsin in low-temperature glasses have been carried out in order to observe directly the risetime of prelumirhodopsin, the first intermediate in the visual pathway. Only at 20 K or below can the risetime of this intermediate be resolved and even at 4 K it is astoundingly rapid, about 36 psec. An examination of the Arrhenius dependence on temperature of the rate of formation of prelumirhodopsin shows a strong deviation from linearity at low temperatures, i.e., non-Arrhenius behavior. This marked non-linear behavior is characteristic of a quantum mechanical tunneling event such as the translocation of hydrogen. An excellent candidate for the tunnelling process is the hydrogen of the protonated Schiff base formed between opsin and its retinal chromophore. Deuterium-exchanged rhodopsin, in which the Schiff base hydrogen is replaced by a deuterium, also shows a marked non-Arrhenius temperature dependence at low temperatures, consistent with tunneling. The rate of formation of prelumirhodopsin in deuterium-exchanged samples is much slower and a deuterium isotope effect kH/kD approximately or equal to 7 is observed. The data support a model in which the formation of prelumirhodopsin involves translocation of a proton toward the Schiff base nitrogen of the retinal chromophore.

Animals↗