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Biomedical subjects

K Kraft

Publications and source records attributed to K Kraft.

At least 109 records · Page 6Linked to original sources
PubMed1986

Clonidine normalizes low plasma beta-endorphin concentration and blood pressure in young men with mild essential hypertension.

In young men with mild essential hypertension and age-matched normotensive volunteers, plasma concentrations of the endogenous opioid beta-endorphin were determined hourly from 9:00 p.m. to 2:00 a.m. The hypertensive patients' mean plasma beta-endorphin concentration was significantly lower in comparison with normotensive controls. After 14 days of treatment with clonidine, systolic and diastolic blood pressure was significantly reduced in both groups. Plasma beta-endorphin concentration increased in the hypertensive patients, but remained unchanged in the normotensive volunteers. The present findings point to a possible involvement of reduced beta-endorphinergic activity in blood pressure regulation of young men with essential hypertension.

Adult↗
PubMed1985

The separate effects of coenzyme components may not be additive. Roles of pyridoxal and inorganic phosphate in aspartate aminotransferase apoenzymes.

Both cytosolic and mitochondrial aspartate transaminase can be resolved of pyridoxal phosphate. The resulting apoenzymes still bind individual structural components of the coenzyme. The separate contributions of coenzyme components to protein thermal stability have been independently assessed for phosphate ions (Pi) and for the pyridoxal or pyridoxamine components of the coenzyme. 31P NMR and differential scanning calorimetry reveal that the thermodynamic contributions of binding are not additive and are dissimilar for the two isozymes. High and low affinity sites for Pi binding are present in both apoenzymes with only the low affinity site being present in the holoenzyme forms. The contribution of both bound phosphates to increasing temperatures (Tm) and enthalpies (delta Hd) of denaturation differ between the isozymes and within sites. In either isozyme occupancy of the high affinity site by Pi produces only a 4- or 5- degree increase in the Tm value with respect to Pi-free apoenzyme. By contrast, in the mitochondrial apoenzyme, the presence of Pi at the second low affinity site increases the calorimetric parameters from Tm = 47 degrees C and delta Hd = 4.7 cal g-1 to Tm = 62 degrees C and delta Hd = 7 cal g-1. For cytosolic apoenzyme the respective changes are from 66 to 69.5 degrees C and 5.2 to 5.8 cal g-1. Addition of pyridoxal, but not pyridoxamine, displaces the high affinity Pi in both apoenzymes. This shows that the pyridine ring and Pi groups of pyridoxal-P bind exclusive of each other when they are not covalently linked as an ester, as in the coenzyme. The observation has been exploited as a method to prepare completely dephosphorylated mitochondrial apoenzyme. Electrostatic effects, structural differences in the phosphate binding pockets, and steric effects can be invoked to account for the Pi and pyridine binding behavior in the two proteins.

Animals↗
PubMed1985

Altered neuropeptide concentrations in spontaneously hypertensive rats: cause or consequence?

Changes in brain neuropeptide content in spontaneously hypertensive rats may be primarily related to the development of hypertension or may be secondary consequences of it. We have measured brain concentrations of beta-endorphin, Leu-enkephalin, arginine vasopressin (AVP) and oxytocin (OXT) in stroke-prone spontaneously hypertensive rats (SHRSP) and in age-matched normotensive Wistar Kyoto (WKY) controls, as well as in SHRSP with normalized blood pressure by chronic treatment with clonidine. Opioid peptide contents were measured in 12-, 18- and 24-week-old rats. beta-Endorphin was measured in the neuro-intermediate and anterior lobes of the pituitary, the hypothalamus, mid-brain and brain stem; Leu-enkephalin in the neuro-intermediate lobe of the pituitary, hypothalamus, mid-brain, brain stem, as well as in the spinal cord and adrenal glands. AVP and OXT were measured in the neuro-intermediate lobe of the pituitary, hypothalamus, brain stem and spinal cord. beta-Endorphin in the neuro-intermediate lobe of the pituitary was significantly higher in 12- and 18-week-old SHRSP. Adrenal gland Leu-enkephalin was lower in SHRSP as compared with the WKY. OXT and AVP contents were markedly reduced in all brain regions of SHRSP except the neuro-intermediate lobe of the pituitary, where no significant changes were found. In no case did long-term antihypertensive treatment with clonidine reverse the altered peptide content in the SHRSP. We conclude that alterations in brain neuropeptide content in SHRSP are not secondary to hypertension. The blood pressure lowering activity of clonidine appears not to depend on major alterations of peptide concentrations. A genetic defect in the synthesis of adrenal enkephalins and hypothalamic OXT and AVP seems likely from these studies.

Animals↗
PubMed1984

Angiotensin stimulates beta-endorphin release from anterior pituitary gland cell cultures of rats.

The effect of exogenous and locally generated angiotensin II (ANG II) on the release of beta-endorphin (beta-END) from anterior pituitary cell cultures of rats was studied. Angiotensin I (ANG I) and ANG II stimulated the release of beta-END, the ANG I effects being inhibited by addition of the converting enzyme inhibitor captopril. Renin and angiotensinogen had no effect when given separately, but their combination increased beta-END release. Thus ANG II causes the release of beta-END, but the putative pituitary renin system cannot be stimulated by exogenous renin or angiotensinogen; converting enzyme, however, acts locally to produce biologically active ANG II from ANG I.

Angiotensin I↗
PubMed1984

Selective tryptic cleavage of native cytoplasmic aspartate transaminase holoenzyme.

The cytoplasmic isozyme of aspartate transaminase is inactivated by trypsin due to loss of a 19-residue peptide from the NH2-terminal region. A second peptide bond at Arg-25 is then cleaved by trypsin leaving a residual core protein, transaminase 26-412. Inactivation by trypsin resembles that for the mitochondrial enzyme (Sandmeier, E., and Christen, P. (1980) J. Biol. Chem. 255, 10284-10289), yet occurs 10 times faster for the cytoplasmic isozyme. In the mitochondrial enzyme, trypsin cleavage produces equal concentrations of proteins missing the first 26 and 31 amino acids. Sequence variation in the NH2-terminal regions can explain such differences. Specifically, the mitochondrial NH2 terminus has no trypsin-susceptible residue at position 19 and is stabilized by an electrostatic interaction between Asp-15 and Arg-292, whereas position 15 is a valyl residue in the cytoplasmic enzyme. Calorimetric data reveal both a decreased transition temperature (Td) and enthalpy (delta Hd) of denaturation in transaminases 20-412 and 26-412. Interaction of substrates with the active site chromophore and differential scanning calorimetry (DSC) reveal that catalytically inactive transaminases 20-412 and 26-412 can bind amino acid substrates and produce spectroscopically detectable conversion of the pyridoxal to the pyridoxamine form of the protein. By contrast, substrate analogs only form enzymatic Michaelis-type complexes.

Amino Acid Sequence↗
PubMed1984

Suppression of plasma prolactin in a patient with a pinealocytoma.

Plasma growth hormone (HGH), prolactin (PRL), luteinizing hormone (LH), thyroid stimulating hormone (TSH), cortisol and melatonin were determined during a 24 h period in a pubertal boy with a pinealocytoma. All hormone concentrations were normal with respect to age and time of day, with the exception of PRL which was undetectable. After subtotal removal of the tumor, basal PRL was still undetectable, but could be stimulated moderately by insulin-induced hypoglycaemia or TRH.

Adolescent↗
PubMed1984

Effect of denervation on the leucine-enkephalin content of the adrenal gland of spontaneously hypertensive rats (SHRSP).

Enkephalins are known to inhibit the release of catecholamines from sympathetic nerve endings. Thus a difference in their turnover rate between SHRSP and normotensive rats (WKY) could contribute to the altered sympathetic activity in SHRSP. One week after denervation which inhibits release of leucine-enkephalin (L-ENK), but not synthesis and processing of the L-ENK precursor, L-ENK increased with the same relative extent in both strains of rats, starting from a lower basal concentration in 7 weeks old SHRSP. In adult rats there was no difference between SHRSP and WKY before and after denervation respectively. It is concluded that the lower content of L-ENK in young SHRSP is caused by an increased release.

Adrenal Glands↗
PubMed1983

Evidence for the presence of enkephalins in the heart.

Extracts of guinea pig hearts were subjected to high performance liquid chromatography (HPLC) and the eluted fractions monitored by radioimmunoassays (RIA) for their content of leucine5-enkephalin (Leu-ENK) and methionine5 enkephalin (Met-ENK). Distinct peaks of both Leu-ENK and Met-ENK immunoreactivity were found corresponding to the position of synthetic Leu-ENK and Met-ENK respectively. The ratio of Leu-ENK to Met-ENK content was about 1:4. Chemical sympathectomy with 5-hydroxydopamine (6-OH-DA) produced a dramatic fall in noradrenaline content of the heart by more than 99%, whereas the concentration in Leu-ENK was reduced by only 70%. The Leu-ENK content of the adrenal glands was not affected by this treatment. These observations point to an enkephalinergic innervation of the heart which appears to be mainly of sympathetic origin. The results suggest the participation of enkephalins in cardiac reflex mechanisms.

Animals↗
PubMed1983

Differential regulation of beta-endorphin in the anterior pituitary, intermediate lobe, hypothalamus and brain stem.

The influence of adrenalectomy (adx), betamethasone (BET) and 11-deoxycorticosterone (DOC) on beta-endorphin-like-immunoactivity (beta-END-LI) in plasma, anterior (AP) and neuro-intermediate lobe (N-IL) of pituitary, hypothalamus (HT) and brain stem (BS) was studied in rats. One day or three weeks after adx animals were injected i.m. for five consecutive days with 0.4mg/kg BET or 3.4mg/kg DOC. Six days after adx beta-END-LI was increased in BS and plasma after four weeks there was an elevation in plasma and AP. BET suppressed beta-END-LI in plasma of both sham-adx and adx animals six days after operation and in the N-IL after six days of adx. DOC led to an increase of beta-END-LI in HT after sham-adx and to a reduction in the N-IL after four weeks of adx. These observations demonstrate that beta-END-LI is regulated differently at its sites of synthesis in the AP, N-IL and HT.

Adrenalectomy↗
PubMed1982

Evidence against co-storage of enkephalins with noradrenaline in bovine adrenal medullary granules.

Bovine adrenal chromaffin granules were purified and separated into adrenaline (A) and noradrenaline (NA) containing granule populations by a combination of differential and isopycnic gradient centrifugation. The distribution of [Leu5]enkephalin as measured by radioimmunoassay followed a pattern identical to adrenaline but not noradrenaline on centrifugation. This suggests that enkephalins are stored in the same type of granule where adrenaline is found or that enkephalins and adrenaline even coexist in one and the same granule. Enkephalins may therefore function as co-transmitters or co-hormones of adrenaline rather than noradrenaline in the adrenal medulla.

Adrenal Medulla↗
PubMed1982

Ultrasonographic diagnoses of major lymphatic system abnormalities prior to 20 weeks of pregnancy.

Prenatal ultrasound diagnoses of severe lymphatic system abnormalities were obtained in three fetuses. In all three cases the diagnosis was established prior to 20 wk of pregnancy, i.e. early enough to allow selective termination. In all three cases male fetuses with a chromosomal anomaly were found. Alpha-fetoprotein values were not elevated. In all cases the fetal abnormalities were of such size that surgical excision could not be taken into consideration to provide satisfactory results for the infants.

Abortion, Therapeutic↗
PubMed1982

LH pattern in ovariectomised rats after continuous blood withdrawal: effects of different substitutions.

Plasma concentrations of LH and of sodium, potassium, total protein and haemoglobin were measured in ovariectomised rats during continuous blood withdrawal up to 180 min; 0.45 ml blood samples were taken every 10 min, the total volume of blood removed not exceeding 9 ml. Four groups of animals were studied: group A received no substitution (controls), group B was substituted with 0.9% NaCl-solution, group C with 3.5% polypeptide solution (Haemaccel), and group D with a suspension of washed erythrocytes from the blood removed. During blood withdrawal, the mean values of LH concentrations as well as the amplitudes of the rhythmic LH pulses remained constant in all the animals. However, the rate of pulses was reduced in the control animals and in the group receiving 0.9% NaCl-solution during the period between 90 and 180 min; in contrast no change was observed in the groups C and D during the whole period. The results presented here show that the characteristic LH pattern in ovariectomised rats is not affected by volume depletion, provided the blood is replaced by a solution containing either a polypeptide or a suspension of washed erythrocytes.

Animals↗
PubMedDate not supplied

DNA aneuploidy by flow cytometry is an independent prognostic factor in squamous cell carcinoma of the oral cavity.

BACKGROUND: The clinical significance of flow cytometric DNA content in head and neck squamous cell carcinoma is still controversial. PATIENTS AND METHODS: We prospectively investigated the prognostic importance of tumor size (T), lymph node involvement at presentation (N), degree of histologic differentiation (G) and DNA ploidy (DNA) in 429 surgically treated patients with primary oral squamous cell carcinoma using multivariate statistics. RESULTS: T, G and DNA were independent predictors of metastasis to the neck. N and DNA were independent prognostic factors of loco-regional recurrence development. N and T were prognostic of overall survival. N and DNA were predictive of recurrence-free survival. For the neck negative group, DNA remained as the only predictor of overall and relapse-free survival. CONCLUSION: DNA flow cytometry adds significant prognostic information beyond that provided by established prognostic factors.

Analysis of Variance↗