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Biomedical subjects

H W Klein

Publications and source records attributed to H W Klein.

At least 37 records · Page 2Linked to original sources
PubMed1988

Use of magnetic resonance spectroscopy in the evaluation of skin flap circulation.

The assessment of events that occur in elevated skin flaps has been largely by indirect methods. A method was sought that gives direct, reproducible, and accurate data about physiological and biochemical changes that occur during flap elevation and during periods of altered blood flow. Because of its ability to monitor changes in the levels of high energy phosphorus metabolites (ATP or adenosine triphosphate, PCr, or phosphocreatin, Pi, or inorganic phosphate), 31p magnetic resonance spectroscopy (MRS) holds promise of providing direct assessment of the metabolic status and biochemical changes that occur during skin flap elevation. MRS monitoring was performed on raised abdominal skin flaps of 12 rats. Abdominal flaps in 4 animals served as controls with and without total vascular occlusion while arterial blood flow was manipulated in 4 flaps and venous flow in 4 flaps. The results have validated the ability of MRS to determine cellular levels of ATP, PCr, and Pi in skin flaps, and to measure intracellular pH through the chemical shift of the Pi resonance.

Adenosine Triphosphate↗
PubMed1988

Pulmonary arterial tree: growth of the tunica media during the first ten years of life.

The developmental changes in the tunica media of the pulmonary trunk and left and right pulmonary arteries were studied in 51 hearts and the great vessels of infants and children up to the age of ten years who died from non-vascular diseases. The internal diameters of the pulmonary arterial tree were measured together with the thickness of the tunica media and the packing density of its elastic fibres. In spite of the age-related (about sixfold) increase in the internal diameters of the vessels there were no parallel significant changes in the characteristics of their tunica media. Furthermore, the configuration of the elastic fibres showed no clear age-related changes in any of the vessels. In conclusion the structure of the wall of the pulmonary trunk and of the pulmonary arteries, although different in embryological origin, seems to show the same pattern of growth during bodily development, with absence of significant correlations between the internal diameters on the one hand and media thickness and packing densities of the elastic fibres on the other. This is possibly the result of the low pulmonary blood pressure.

Age Factors↗
PubMed1987

Recovery of free muscle grafts in rat: improvement is associated with an increase in cyclic adenosine monophosphate concentration or use of the condition/test paradigm.

The muscle fibers in freely grafted skeletal muscles degenerate and are replaced by new fibers which develop within the graft. Myogenesis in regenerating muscle recapitulates, to a large extent, developmental myogenesis and may depend on similar modulating influences. In addition to the generation of new fibers, functional recovery of free muscle grafts also requires reinnervation and revascularization of the new fibers. Recovery of function should be improved by enhancing either myogenesis or reinnervation and revascularization. We have used two procedures, shown previously to stimulate peripheral nerve regeneration, to improve the morphologic and functional recovery of free, orthotopic grafts of rat extensor digitorum longus muscle. Each of the procedures was effective, but had potentially different sites of action. The first procedure, the condition/test paradigm, presumably increases the rate and extent of graft reinnervation. The second procedure, continuous infusion of the adenylate cyclase activator forskolin during the first 21 days after grafting, may influence both myogenesis and nerve regeneration. Each procedure increased regenerating muscle fiber size and functional capacity, and forskolin also significantly increased capillary density and fatigue resistance.

Animals↗
PubMed1987

Growth of the internal diameters in the pulmonary arterial tree in infants and children.

To provide a better understanding of the operability of the pulmonary arteries in children with tetralogy of Fallot or with pulmonary atresia, we investigated the growth of the internal diameters of the pulmonary arterial tree in fresh postmortem hearts and great arteries of infants and children of ages up to 10 years after birth, who died from non-vascular diseases. Linear correlations were found between, on the one hand, the internal diameters of the pulmonary ostium, pulmonary trunk and left and right pulmonary artery and, on the other, body length. Based on an approach used in clinical studies we also determined the ratios between the internal diameter of the pulmonary arterial tree and the ascending aorta and also the ratios of the internal diameters of the descending aorta and the sum of the size of the left and right pulmonary arteries. Comparison of the data from the postmortem material with observations on the internal diameters measured with two dimensional (sector) echocardiography echo indicates that the latter may slightly underestimate the true diameters.

Anthropometry↗
PubMed1986

Mechanism of the phosphorylase reaction. Utilization of D-gluco-hept-1-enitol in the absence of primer.

alpha-Glucan phosphorylases from rabbit skeletal muscle, potato tubers and Escherichia coli catalyze the utilization of 2,6-anhydro-1-deoxy-D-gluco-hept-1-enitol (heptenitol) in the presence of arsenate or phosphate. 1H-NMR analysis in the presence of 2H2O and arsenate indicated formation of 1-[1-2H]deoxy-alpha-D-glucoheptulose with rates comparable to the arsenolysis of poly- or oligosaccharides. The reaction depends on the presence of a dianionic 5'-phosphate group of pyridoxal in the active conformation of the phosphorylases. Heptenitol is the first known substrate of alpha-glucan phosphorylases which does not require a primer. This is explained by the finding that heptenitol is exclusively used as substrate for the degradative pathway of the phosphorylase reaction where it competes with polysaccharide substrates. In the presence of phosphate the reaction product is 1-deoxy-alpha-D-gluco-heptulose 2-phosphate (heptulose-2-P), which subsequently inhibits the reaction. This characterizes heptulose-2-P as an enzyme-derived inhibitor. The Ki = 1.9 X 10(-6) M with potato phosphorylase suggests the formation of a transition-state-like enzyme-ligand complex. These findings, together with the fact that the phosphates of heptulose-2-P and pyridoxal 5'-phosphate are linked by hydrogen bridges [Klein, H. W., Im, M. J., Palm, D. & Helmreich, E. J. M. (1984) Biochemistry 23, 5853-5861], make it likely that both phosphates are involved in phosphorylase catalysis. A catalytic mechanism of phosphorylase action is proposed in which a 'mobile' phosphate anion plays a versatile role. It serves as proton carrier for the substrate activation, it stabilizes the intermediate and acts as a nucleophile which can accept a glycosyl residue reversibly.

Animals↗
PubMed1986

Reconstitution of beta 1-adrenoceptor-dependent adenylate cyclase from purified components.

In continuation of our efforts to reconstitute from purified components into lipid vesicles the signal transmission chain from beta 1-adrenoceptors to adenylate cyclase, we now report on the total reconstitution of the hormone-dependent adenylate cyclase. In these reconstitution experiments we have employed the purified adenylate cyclase (C) from bovine brain and rabbit heart, the stimulatory GTP-binding protein (GS) purified from turkey erythrocytes and rabbit liver and the beta 1-adrenoceptor (R) from turkey erythrocytes. Several detergents were compared with respect to their suitability to allow reconstitution of subunits into phospholipid vesicles. While octyl-polyoxyethylene (octyl-POE) was almost as potent as lauroyl-sucrose for preparation of vesicles containing GS.C, the latter detergent was clearly superior for vesicles enabling productive R.GS and R.GS.C coupling. The catalytic subunit from either bovine brain or rabbit heart was equally efficient in reconstitution. However, GS from turkey erythrocytes and rabbit liver revealed significant differences in RGS and RGS.C containing vesicles. While isoproterenol-induced activation of GS by GTP gamma S was first order in both instances, kon with turkey GS was 0.12 min-1, whereas kon with rabbit liver GS was 0.6 min-1. Moreover, GTP gamma S activation of erythrocyte GS was significantly more dependent on the presence of hormone than that of liver GS, confirming observations made on the native membrane-bound system. Compared with stimulation by isoproterenol (GTP gamma S) (4-fold), stimulation by isoproterenol/GTP was modest (1.3- to 1.6-fold).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1986

Gastric carcinoma: intestinal metaplasia and tumor growth patterns as indicators of prognosis.

We have reviewed 200 cases of gastric carcinoma treated between 1970 and 1980 to assess the value of intestinal metaplasia in the stomach and tumor growth patterns in determining prognosis. Intestinal metaplasia was found to be more frequently associated with early gastric tumors, expanding-type tumors, and tumors located in the antrum. The survival rate was 53% with intestinal metaplasia and 34% without. Sixty-three percent of expanding tumors with metaplasia survived. If the lymph nodes were not involved, the survival rate with metaplasia was 81%. We conclude that intestinal metaplasia and growth patterns are valuable in predicting outcome. Preoperative evaluation of gastric tumors should include multiple endoscopic mucosal biopsy specimens. If intestinal metaplasia is present, the improved possibility of survival should influence the surgeon in the choice of operative treatment.

Female↗
PubMed1984

Reconstitution of beta-adrenergic receptor with components of adenylate cyclase.

Beta 1-Adrenergic receptor proteins were extracted from turkey erythrocyte membranes with lauroyl sucrose and digitonin and purified by affinity chromatography on a column of alprenolol agarose Affi-gel 10 or 15. The 5000-fold purified receptor is able to couple functionally with the stimulatory GTP-binding protein (GS) from either turkey or duck erythrocytes. Functional coupling was achieved by three different approaches. (i) Purified beta-receptor polypeptides were coupled in phospholipid (asolectin) vesicles with GS from a crude cholate or lauroyl sucrose extract of turkey erythrocyte membranes. The detergent was removed and vesicles were formed with SM-2 beads. (ii) Purified beta-receptor was reconstituted with pure, homogeneous GS in asolectin vesicles. (iii) Purified beta-receptors were either coupled in asolectin vesicles with a mixture of pure, homogeneous Gpp(NH)p-activated GS and a lauroyl sucrose extract of turkey erythrocyte membranes, or with pure, homogeneous Gpp(NH)p-activated GS alone. The decay of activity was measured on addition of GTP and hormone. In (ii) and (iii), the detergent was removed and vesicles were formed by gel filtration on Sephadex G-50 columns. In each of the three different experimental conditions, the beta-receptor was activated with l-isoproterenol and activation was blocked with d,l-propranolol. Activated GS were measured separately by means of their capacity to activate a crude Lubrol PX-solubilized adenylate cyclase preparation from rabbit myocardial membrane. The kinetics of GS activation by purified beta-receptors occupied by l-isoproterenol was first order and activation was linearly dependent on receptor concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1984

Does pyridoxal 5'-phosphate function in glycogen phosphorylase as an electrophilic or a general acid catalyst?

alpha-D-Glucose 1-diphosphate interacts with pyridoxal-reconstituted rabbit muscle phosphorylase b activated by AMP (AMP-S). Under these conditions, the glucose moiety of alpha-D-[14C]glucose 1-diphosphate is transferred to limit dextrin forming alpha(1----4) glycosidic bonds and simultaneously releasing pyrophosphate as shown by 31P NMR spectroscopy. Thus, specific structural requirements invoked to explain the reactions of pyridoxal(5')diphospho(1)-alpha-D-glucose need not to be assumed in the case of the reactions of alpha-D-glucose 1-diphosphate. Dianions isomorphous to phosphate activate pyridoxal phosphorylase regardless of their pK values while the same anions, when bound covalently to pyridoxal, are inactive. Thus, anions bound noncovalently to pyridoxal phosphorylase act differently than anions linked covalently to pyridoxal, such as the 5'-phosphate group of pyridoxal 5'-phosphate, which is postulated to be part of a proton donor-acceptor pathway. The reaction of 2,6-anhydro-1-deoxy-D-gluco-hept-1-enitol (heptenitol) with phosphorylase yields, in the presence of orthophosphate as a glycosyl acceptor, 1-deoxy-D-gluco-heptulose 2-phosphate (heptulose-2-P). This sugar phosphate is unreactive but a potent competitive inhibitor for rabbit muscle phosphorylase b and potato phosphorylase with respect to alpha-D-glucose 1-phosphate: Ki = 14 X 10(-6) M and 1.9 X 10(-6) M, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Substrate-cofactor interactions for glycogen phosphorylase b: a binding study in the crystal with heptenitol and heptulose 2-phosphate.

The structural relationships between substrate and pyridoxal phosphate in glycogen phosphorylase b (EC 2.4.1.1) have been studied by X-ray diffraction experiments at 3-A resolution. Recent work [Klein, H. W., Im, M. J., & Helmreich, E. J. M. (1984) in Chemical and Biological Aspects of Vitamin B6 Catalysis (Evangelopoulos, A. E., Ed.) pp 147-160, Liss, New York] has shown that phosphorylase in the presence of inorganic phosphate catalyzes the conversion of heptenitol to heptulose 2-phosphate. The latter compound is a dead-end product and a most potent inhibitor (Ki = 14 microM). The X-ray diffraction studies show that heptenitol binds at the catalytic site of phosphorylase in a position essentially identical with that observed for the glucopyranose moiety of glucose 1-phosphate. Incubation of a phosphorylase b crystal for 50 h in a solution containing the substrates heptenitol and inorganic phosphate and the activators AMP and maltohetaose resulted in the formation of a phosphorylated product bound at the active site. The structure of this product, as analyzed by a difference Fourier synthesis at 3 A, is consistent with that of heptulose 2-phosphate. Analysis of the surrounding soak solution by thin-layer chromatography showed that heptulose 2-phosphate was produced under these conditions. Heptulose 2-phosphate binds with its glucopyranose moiety in the same position as that for glucose 1-phosphate, but there is a marked difference in phosphate positions. The presence of the methyl group in the beta-configuration in heptulose 2-phosphate forces a change in the torsion angle O5-C1-O1-P from 117 degrees as observe in glucose 1-phosphate to -136 degrees in heptulose 2-phosphate. The "down" position of the phosphate (with respect to the crystallographic z axis) results in a change in the distance between the 5'-phosphorus atom of the pyridoxal phosphate and the phosphorus atom of the substrate from 6.8 (with glucose 1-phosphate) to 4.5 A (with heptulose 2-phosphate). The closest distance between the phosphate oxygen of the cofactor and a phosphate oxygen of heptulose 2-phosphate is 2.7 A, and it is assumed that there must be a hydrogen bond between them. These observations are consistent with the NMR experiments reported in the preceding paper in which sharing of a proton between heptulose 2-phosphate and pyridoxal 5'-phosphate is observed [Klein, H.W., Im, M. J., Palm, D., & Helmreich, E. J. M. (1984) Biochemistry (preceding paper in this issue)].(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Monophosphate↗
PubMed1984

Histo-anatomical backgrounds of subclavian flap aortoplasty in coarctation of the aorta.

After repair of coarctation of the aorta using the technique of resection and end-to-end anastomosis, the internal diameters of the aortic isthmus and descending aorta often fail to increase. Better results seem possible with aortoplasty using the left subclavian flap technique. In order to clarify this matter, we investigated the structure of the left subclavian artery comparing it with that of the descending aorta and aortic isthmus: we studied the internal diameter, the thickness of the tunica media and the packing density of its elastic fibers in these vascular elements using a postmortem material of children with a coarctation of the aorta. The ages ranged from 4 days to 13 months with one child of 8 years. All 16 cases had one or more additional cardiac lesions. Operation had been performed in 3 children: 2 end-to-end anastomoses and one subclavian bypass of the aortic arch. Data were compared with observations on autopsy cases of children without cardiovascular abnormalities. The mean findings were that the calibers of the left subclavian artery and the descending aorta were within normal limits but that the caliber of the aortic isthmus was smaller than in normal children. The measurements on the tunica media showed that although, generally, the thickness of the media of the left subclavian artery was smaller than that of the aortic isthmus and descending aorta of the same individual, it contained relatively more elastic fibers than the matching vessels. This may indicate that the structure of the left subclavian artery is well suited to grow out as a part of the aortic arch.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1983

alpha-Glucan phosphorylases catalyze the glucosyl transfer from alpha-D-glucosyl fluoride to oligosaccharides.

Regulated and nonregulated phosphorylases were found to catalyze in a slow, orthophosphate dependent reaction the direct transfer of the glucosyl residue from alpha-D-glucosyl fluoride to an oligosaccharide primer. The enzyme catalyzed formation of the glucosyl residue requires stereospecific protonation of alpha-D-glucosyl fluoride by a Brønstedt acid. The results are interpreted by a mechanism whereby phosphate acts as a proton shuttle and the cofactor pyridoxal 5'-phosphate is required to promote the acid-base function of phosphate.

Animals↗
PubMed1983

Comparison of the growth of the tunica media of the ascending aorta, aortic isthmus and descending aorta in infants and children.

This study concerns the normal histological growth of the aorta in infants and children. We measured, in post mortem material consisting of 69 hearts and great vessels of infants and children who died from non-vascular diseases, the internal diameters of the ascending aorta, aortic isthmus and descending aorta together with the thickness of the tunica media and the packing density of its elastic fibres. Age range was from 27 weeks of gestational age up to 10 years after birth. The growth of the tunica media of the ascending aorta was, in part, different from that of the aortic isthmus and descending aorta. Notwithstanding an increase in the thickness of the tunica media parallelling, in all three parts of the aorta, an increase in their internal diameters, the packing density of the elastic fibres of the tunica media of the aortic isthmus and of the descending aorta showed no tendency to increase with age. However, the packing density of the elastic fibres of the ascending aorta showed a continuing increase with age parallelling the increase of the internal diameter. This can probably be better explained as a result of functional difference than as a result of different embryological origin.

Aorta↗
PubMed1982

General acid-base catalysis of alpha-glucan phosphorylases: stereospecific glucosyl transfer from D-glucal is a pyridoxal 5'-phosphate and orthophosphate (arsenate) dependent reaction.

D-Glucal, containing a highly reactive double bond, can replace glucose 1-phosphate as the glucosyl donor in phosphorylase-catalyzed glucosyl transfer to a suitable oligo- or polysaccharide acceptor: D-glucal + Pi + (glucose)Pi leads to n 2-deoxy-alpha-D-glucosyl(glucose)n in equilibrium 2-deoxy-alpha-D-glucose-1-P + (glucose)n. This reaction is catalyzed by alpha-glucan phosphorylases from rabbit skeletal muscle, potato tuber, and Escherichia coli. D-Glucal is only measurably consumed by alpha-glucan phosphorylases when orthophosphate or arsenate is present. With saturating concentrations of these anions and a glucosyl acceptor, the D-glucal reaction proceeds at rates comparable with the rates of glucosyl transfer from glucose 1-phosphate and of phosphorolysis or arsenolysis of poly- or oligosaccharides. Furthermore, for the reaction to proceed, the enzyme must be in the active conformation containing the cofactor pyridoxal 5'-phosphate in its dianionic form. On the basis of proton nuclear magnetic resonance spectra, it is proposed that protonation at C-2 of D-glucal gives rise to a hypothetical 2-deoxy-beta-D-glucose intermediate, yielding as a final product (2-deoxy-alpha-D-[2(e)-2H]glucose)n alpha (1 leads to 4) saccharides. These 2-deoxy-alpha-D-glucose oligo- or polysaccharides are degraded by alpha-glucan phosphorylases by phosphorolysis or arsenolysis like natural linear and branched alpha-glucans. The absolute requirement of the D-glucal reaction for phosphate (or arsenate) and its dependency on the dianionic form of the pyridoxal 5'-phosphate bound to phosphorylase are rationalized in terms of a proton transfer relay involving juxtaposed phosphates. Phosphate--phosphate interactions were postulated by Withers et al. [Withers, S. G., Madsen, N. B., Sykes, B. D., Takagi, M., Shimomura, S., & Fukui, T. (1981) J. Biol. Chem. 256, 10759-10762].

Arsenates↗
PubMed1982

Reduction mammaplasty with inferiorly based glandular pedicle flap.

We have reduced 60 breasts in 30 women using an inferiorly based glandular pedicle. Our complication rate has been extremely low and the technique offers major time-savings. Our method prevents the serious postoperative breast deformities frequently resulting from traditional methods of breast reduction.

Breast↗