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Biomedical subjects

L M Greenbaum

Publications and source records attributed to L M Greenbaum.

At least 37 records · Page 2Linked to original sources
PubMed1985

Release of T-kinin and bradykinin in carrageenin induced inflammation in the rat.

Plasma and inflammatory fluid kininogen levels, and blood and inflammatory fluid free kinin levels were determined in rats 24 h after the injection of carrageenin into an air pouch. Plasma T-kininogen levels increased 7-fold. In the inflammatory fluid levels reached 8 micrograms/ml. Blood levels of free kinin showed a 5-fold increase. The kinins were identified on HPLC as T-kinin (Ile-Ser-bradykinin) and bradykinin, 63 and 37%, respectively. These results indicate for the first time that free T-kinin as well as bradykinin is released during an inflammatory response in rat and confirms our previous finding that T-kininogen may be a major acute-phase protein in inflammation.

Animals↗
PubMed1985

T-kininogen--the major plasma kininogen in rat adjuvant arthritis.

Total kininogen in plasma of Freund's adjuvant treated rats increased 20-fold 7 days following the injection. Analysis of the kininogens demonstrated that increases in T-kininogen was the major reason for the rise in kininogen. High molecular weight and low molecular weight kininogens showed little or no change. The increase in T-kininogen paralleled the inflammatory condition. Anti-inflammatory agents which reduced paw swelling also reduced plasma T-kininogen levels. Unidentified peaks on HPLC of kinin following plasma treatment by trypsin were shown to be oligopeptides containing T-kinin (Ile-serbradykinin). The relationship of T-kininogen to the inflammatory response is discussed.

Animals↗
PubMed1984

Guanine nucleotide sensitivity of muscarinic acetylcholine receptors from rat brainstem is eliminated by endogenous proteolytic activity.

The sensitivity to guanine nucleotides of agonist binding to muscarinic acetylcholine receptors was eliminated by incubating rat brainstem membranes at 37 degrees C for 30 min. Pretreatment with any of a variety of proteinase inhibitors prevented this loss of sensitivity. In contrast to other treatments which inactivate guanine nucleotide regulatory mechanisms of muscarinic receptors, incubation at 37 degrees C did not alter agonist binding measured in the absence of guanine nucleotides. Endogenous proteolytic activity appears to inactivate the nucleotide regulatory subunit without engendering its dissociation from the receptor binding subunit.

Animals↗
PubMed1984

Detection and quantitation of fluorescamine-labeled bradykinin, its analogues and metabolites using high-performance liquid chromatography.

A sensitive technique is described for detecting and quantitating fluorescamine-labeled kinins and their usual metabolic products using reversed-phase high-performance liquid chromatography (HPLC) linked with a fluorescence detector. Kinins and their enzymatic products were labeled with fluorescamine, subjected to HPLC, and scanned for the fluorescence signal with excitation at 390 nm and emission at 476 nm. The fluorescence signal was linear with bradykinin, Lys-bradykinin and Met-Lys-bradykinin in amounts upward from 2.5 ng. Separation of the fluorescamine-labeled kinins using HPLC was carried out with a solvent system of methanol-triethylammonium formate buffer. Labeled kinins were eluted in the following order: bradykinin, Lys-bradykinin, and Met-Lys-bradykinin. When native (unlabeled) kinins were subjected to HPLC using a solvent system of acetonitrile-triethylammonium formate buffer, the minimum amount of native kinin detected at 210 nm was 1 microgram. All three kinins showed linearity at 210 nm in amounts upward from 1 microgram. Kinins were eluted in the following order: Lys-bradykinin, bradykinin and Met-Lys-bradykinin. The different elution patterns of kinins by means of these two separation techniques provide a useful method for identification of purified kinins. The fluorescamine label provides a 400-fold more sensitive detection technique than ultraviolet absorbance of the native kinins and may be used to identify the metabolic products of kinins.

Aminopeptidases↗
PubMed1984

From adrenoceptor mechanisms to clinical therapeutics: Raymond Ahlquist, Ph.D., 1914-1983.

Identification of two distinct types of adrenotropic receptors, alpha and beta, by Raymond Ahlquist provided the scientific basis that enabled the development of drugs to selectively block adrenoceptor function. These pharmacotherapeutic advances have improved the care of patients with coronary and hypertensive cardiovascular disease.

Adrenergic beta-Antagonists↗
PubMed1983

Isolation and structure of T-kinin.

T-kinin, a previously undescribed peptide containing bradykinin, has been isolated following treatment of rat plasma with trypsin (1 mg/ml). The liberated T-kinin, which contracts the rat uterus, was isolated by procedures including OM-cellulose, Biogel P-4 and reverse-phase high-performance liquid chromatography. The final material had a single N-terminal isoleucine and was shown by amino acid analysis and sequence determination to have the structure of the undecapeptide Ile-Ser-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg (isoleucyl-seryl-bradykinin). The relationships of the protein from which T-kinin is cleaved (T-kininogen) to other known kininogens is discussed.

Amino Acid Sequence↗
PubMed1983

Kininogen substrates for trypsin and cathepsin D in human, rabbit and rat plasmas.

Studies have compared "total", HMW kininogen and leukokininogen levels in human, rabbit and rat plasma using trypsin, glass powder and cathepsin D as kininogenases or activators of kininogenases. Rat plasma was found to have about 10 fold more leukokininogen than the other plasmas assayed. When trypsin was used to estimate total kininogen, rat plasma liberated maximal amounts of kinin only in the presence of high concentrations of trypsin (1 mg/ml incubation mixture). In addition, it was found that trypsin in these concentrations liberated from rat plasma both bradykinin and a previously unidentified kinin which we have termed "T-kinin". The results overall indicate that in the case of rat and rabbit plasma, currently used methods for estimations of total kininogen may not be accurate. T-kinin may represent a leukokininogen or a hitherto undescribed kininogen.

Animals↗
PubMed1983

Paradoxical effect of leupeptin in vivo on cathepsin B activity.

Leupeptin is a potent inhibitor of cathepsin B in vitro and is presumed to act in a similar manner in vivo. It is currently being used in several laboratories to examine the role of lysosomal proteinases such as cathepsin B in mouse models of muscular dystrophy. This report clearly demonstrates that leupeptin in adequate concentrations in vivo, is a potent stimulator of cathepsin B activity in striated muscle, heart, liver and kidney of the mouse. This paradoxical effect indicates that care is required in the interpretation of the results of the use of leupeptin as a cathepsin B inhibitor in vivo and that its use as an antiprotease for therapeutic purposes may be limited. Studies on CBZ-Phe-Ala-CHN2 demonstrated that this agent, when administered in vivo, inhibited Cathepsin B in the tissues assayed.

Animals↗
PubMed1983

Host cathepsin D response to tumor in the normal and pepstatin-treated mouse.

In view of the postulated role of cathepsin D in cachexia, investigations have been pursued on the host tissue response of cathepsin D activity in DBA/2 mice inoculated with 5 X 10(5) L1210 tumor cells. The results confirmed previous investigators' findings of the increase in cathepsin D activity (specific activity) in liver and muscle of tumor bearers. In addition, it was found that this increase was a general response of the host since heart, kidney, lung, and spleen cathepsin D specific activity were also enhanced in tumor bearers. These increases ranged from an average of 10% for spleen to 100% for gastrocnemius muscle. This effect was age related in heart and kidney. As a working hypothesis, we propose the concept that tumor bearers release protease-enhancing factor(s) which trigger increase or enhancement of cathepsin D activity in host tissues by yet unknown mechanisms. Pepstatin (60 mg/kg), a known inhibitor of cathepsin D in vitro, was shown to provide long-lasting inhibition (3 to 6 days) of cathepsin D in vivo in non-tumor bearers particularly in spleen, liver, kidney, lung, and heart. Evidence is provided from assays of cell fractions that this inhibition takes place at or in the lysosome. The duration of the effectiveness of pepstatin was altered in tumor bearers in that cathepsin D activity of heart, lung, and spleen had returned to near normal values in 48 hr following pepstatin injection. However, in muscle, liver, and kidney, significant inhibition (90%) still persisted in tumor bearers as it did in non-tumor bearers. Pepstatin or related antiproteases may prove useful as "anticachexia" agents by decreasing proteolysis in muscle and other tissues.

Age Factors↗
PubMed1982

Effects of pepstatin on reducing hypoxia-induced injury in the isolated guniea pig heart.

Intracellular cathepsin D is thought to play a role in myocardial injury produced by ischemia and hypoxia. Pepstatin, a known inhibitor of cathepsin D, was infused into isolated guniea pig hearts (Langendorff preparation) in order to observe if such an administration of pepstatin would protect against the effects of a two minute exposure to hypoxia. Hypoxia was produced by exposing the hearts to perfusion fluid aerated with 20% 02/5% CO2/75% N2 and containing 0.5 microgram/ml of norepinephrine. Contractile force, heart rate, coronary flow and ECG were monitored. Samples of heart tissue were assayed for cathepsin D activity. Infusion of 0.06 mg/min of pepstatin for 30 minutes produced no significant alterations in the parameters of cardiac function studied. However, this amount of pepstatin inhibited 97% of the cathepsin D activity of the hearts. The characteristics ECG alterations produced by hypoxia were significantly reduced after infusion of pepstatin. These data indicate that pepstatin may protect the heart against hypoxia-induced injury.

Animals↗
PubMed1981

Use of fluorescent probes that form intramolecular excimers to monitor structural changes in model and biological membranes.

1,3-dipyrenylpropane (PC3P) and bis(4-biphenylmethyl)ether, two molecules that form intramolecular excimers, were embedded in phospholipid vesicles and biological membranes to monitor dynamic properties of membrane lipids. Excimer formation was evaluated from determinations of excimer to monomer emission intensity ratios (ID/IM). ID/IM values of PC3P and bis(4-biphenylmethyl)ether were reduced when cholesterol was added to egg lecithin vesicles. PC3P was sensitive to the temperature-induced crystalline to liquid-crystalline phase transition in dimyristoyl phosphatidylcholine vesicles. For studies of cellular membranes, membranes, PC3P was used exclusively, because of the fluorescence of tryptophan residues of membrane proteins interferes with the responses bis(4-biphenylmethyl)ether. Microviscosities of membrane interiors were calculated from standard curves of IM/ID plotted against solvent viscosity. Microviscosity values of egg lecithin vesicles and biological membranes, especially those obtained with PC3P, were more than an order of magnitude lower than values obtained by other techniques. We concluded that the intramolecular process leading to the formation of the excimer is influenced differently in isotropic solvents than in anisotropic environments, such as lipid bilayers. Although distinguishable ID/IM ratios can be obtained for different biological membranes (mitochondrial, microsomal, and plasma membranes were studied), this parameter may be phenomenological and not simply related to membrane microviscosity. As such, fluorescent probes that form intramolecular excimers are of value in making qualitative comparisons of different membranes and in studying the relative effects of physical changes and chemical agents on membrane structure. These probes may also be valuable for studying structural anisotropy of biological membranes.

Animals↗
PubMed1980

Angiotensin I conversion and vascular reactivity in pathophysiological states in dogs.

To determine if angiotension converting enzyme activity is altered by acute pathophysiological insults, we assessed angiotensin I conversion using a blood pressure response technique in anesthetized dogs studied during acute 100% O2 breathing and acute acid-base derangements. Also, we determined systemic vascular reactivity to angiotensin II by measuring the magnitude and duration of the arterial blood pressure response to intra-arterial injections of angiotensin II under these same conditions. Angiotensin I conversion found in normoxia [91 +/- 7 (SD)%] was unchanged by acute acidosis, alkalosis, and hyperoxia. During acute hyperoxia the mean half time of the hypertensive response increased from 68 +/- 25 (SD) s at a PaO2 of 112 +/- 18 (SD) Torr to 100 +/- 34 (SD) s at a PaO2 of 491 +/- 47 (SD) Torr (P less than 0.01). No other pathophysiological condition studied had any effect on reactivity of systemic vasculature to angiotensin II. We conclude that, except during acute hypoxia as previously shown, converting enzyme activity is resistant to other pathophysiological insults and that vascular responsiveness to angiotensin II is enhanced by hyperoxia.

Acid-Base Imbalance↗