Biomedical subjects

J Pitha

Publications and source records attributed to J Pitha.

At least 19 recordsLinked to original sources

PubMed1999

Does angiotensin-converting enzyme polymorphism influence the clinical manifestation and progression of heart failure in patients with dilated cardiomyopathy?

To evaluate the role of angiotensin-converting enzyme (ACE) polymorphism on the development of end-stage dilated cardiomyopathy, the ACE gene polymorphism of 90 patients after heart transplantation because of this disease was compared with the population sample. No difference in gene frequencies was found, but when compared with the population sample there were fewer ID heterozygotes detected; no significant influence of ACE polymorphism on the course of the disease before transplantation was found.

Adult↗

PubMed1999

Diffuse glomerular basement membrane lamellation in renal allografts from pediatric donors to adult recipients.

The transplantation of kidneys from pediatric cadaveric donors into adult recipients is performed in many centers. However, some studies indicate that the outcome of such renal transplants may be inferior compared with that of adult donors, particularly if the donor is an infant. Morphologic studies of failed pediatric donor kidneys in adult recipients describe various degrees of segmental or global glomerular sclerosis. The authors have performed ultrastructural examinations on such transplants and have identified six cases with diffuse irregular lamellation of the glomerular basement membrane (GBM), a change that may develop as early as 10 weeks after transplantation. The age of all donors was < or =6 years; three were infants. The incidence of the lesion was 9% at our institution in renal transplant patients who received a graft from donors <10 years old. Diffuse GBM lamellation has not been found in renal transplants from adult donors. Light microscopy showed various degrees of diffuse mesangial expansion, usually with segmental glomerular sclerosis. The patients had severe proteinuria. While recurrent focal segmental glomerular sclerosis (FSGS) has to be excluded, such diffuse GBM lamellation is generally not seen in recurrent FSGS cases. The pathogenesis of the lesion is most likely related to hyperperfusion injury of small pediatric donor kidneys grafted into adult recipients.

Adult↗

PubMed1998

Electrical conduction between the right atrium and the left atrium via the musculature of the coronary sinus.

BACKGROUND: The purpose of this study was to determine whether the coronary sinus (CS) musculature has electrical connections to the right atrium (RA) and left atrium (LA) and forms an RA-LA connection. METHODS AND RESULTS: Six excised dog hearts were perfused in a Langendorff preparation. A 20-electrode catheter (2-4-2-mm spacing center to center) was placed along the CS. Excision of the pulmonary veins provided access to the LA, and a second 20-electrode catheter was placed along the LA endocardium opposite the CS catheter. An incision opened the CS longitudinally, and microelectrodes were inserted into the CS musculature and adjacent LA myocardium. Continuous CS musculature was visible along a 35+/-9-mm length of the CS beginning at the ostium. During lateral LA pacing, CS electrodes recorded double potentials, a rounded, low-frequency potential followed by a sharp potential. The rounded initial potential propagated in the lateral-to-septal direction and represented "far-field" LA activation (timing coincided with adjacent LA potentials and with action potentials recorded from microelectrodes in adjacent LA cells). The sharp potential represented CS activation (timing coincided with action potentials recorded from CS musculature). A distal LA-CS connection (earliest sharp potential in the CS during lateral LA pacing) was located 26+/-7 mm from the ostium. During RA pacing posterior to the CS ostium, CS electrodes recorded septal-to-lateral activation of the high-frequency potential, with slightly later activation of the rounded potential (LA activation). Incisions surrounding the CS ostium isolating the ostium from the RA had no effect on the CS musculature and LA potentials during RA pacing within the isolated segment containing the CS ostium. RA pacing outside the isolated segment delayed activation of the CS musculature until after LA activation, confirming that the RA-CS connection was located in the region of the CS ostium as well as confirming the presence of the LA-CS connection. CONCLUSIONS: In canine hearts, the CS musculature is electrically connected to the RA and the LA and forms an RA-LA connection.

Animals↗

PubMed1998

Evidence for multiple atrio-AV nodal inputs in the normal dog heart.

INTRODUCTION: Complete AV block after combined fast pathway (FP) and slow pathway (SP) ablation is uncommon. The purpose of this study was to interrupt activation of these and additional inputs by placing a radiofrequency lesion across the interatrial septum between the FP and SP ablation sites. METHODS AND RESULTS: In eight anesthetized open chest dogs, FP ablation induced significant A-H prolongation (deltaA-H: 51 +/- 14 msec; P < 0.001) and a shift of earliest retrograde atrial activation from the anterior septum to the region of the coronary sinus (CS) os. Subsequently, ablation of the interatrial septum across the fossa ovalis was successful in 5 of 8 dogs, changing the sequence of atrial activation (A) so that A at the His-bundle electrogram, which initially preceded A at the CS os (18 +/- 4 msec vs 46 +/- 7 msec, P < 0.01), now followed CS os A (81 +/- 31 msec vs 59 +/- 20 msec, P < 0.05). Additional ablation of the SP caused a type II Mobitz AV block or complete AV block in 5 of 8 dogs. The four dogs with complete AV block showed a stable, high junctional escape rhythm at a rate of 64 +/- 16 beats/min. Pacing between the ablation lesions and the AV node in one dog showed 1:1 AV conduction and Wenckebach-type AV block indicating preserved AV nodal function. Histology showed necrotic changes in the FP and SP transitional cell zones and in the atrial tissue of the interatrial septum. However, the compact AV node, His bundle, and adjacent atria and transitional cells were undamaged. CONCLUSION: There are additional AV nodal inputs in the interatrial septum in addition to the anterior FP and posterior SP inputs. Ablation of all of these may be required, if the aim is production of complete AV block proximal to the AV node with a high junctional escape rhythm.

Animals↗

PubMed1997

Angiomatoid malignant fibrous histiocytoma revisited. An immunohistochemical and DNA ploidy analysis.

A histologic, immunohistochemical, and DNA ploidy analyses were performed on two cases of angiomatoid malignant fibrous histiocytoma to ascertain the histogenesis and relationship of endothelial, histiocytic, and fibroblastic elements. Both cases were slowly growing, grossly encapsulated. Subcutaneous masses resected from pediatric patients. Microscopically, the tumors were composed of solid masses of epithelioid and spindle cells with abnormal endothelial-lined and blood-filled cystic spaces surrounded by normal vascular structures and aggregates of lymphocytes occasionally forming germinal follicles. The tumor cells stained exclusively with CD34 and vimentin antibodies. Tumor-associated vessels stained for CD31, CD34, vimentin, and Ulex europaeus. Occasional cells within germinal follicles stained for lysozyme, CD68, and HAM56. Ploidy analysis of tumor cells showed intermediate aneuploidy with a DNA index of 1.14. Blood vessels within and surrounding the tumor as well as inflammatory cells were DNA euploid. These studies suggest that the tumor--though comprised of histologically and immunohistochemically benign-appearing euploid endothelial, fibroblastic, and inflammatory elements--contains an aneuploid population of undifferentiated mesenchymal cells.

Aneuploidy↗

PubMed1997

Electrophysiology of the right anterior approach to the atrioventricular node: studies in vivo and in the isolated perfused dog heart.

INTRODUCTION: Previous reports have described electrophysiologic properties and rate-dependent responses in the transitional cell zone of the posterior AV nodal input (slow pathway). The purpose of this study was to investigate the electrophysiology of the anterior transitional cell zone (fast pathway) in vivo and in a Langendorff preparation perfused with a nonblood solution containing butanedionemonoxime to inhibit contraction. METHODS AND RESULTS: In five anesthetized dogs, the His-bundle electrogram recorded from the aortic root included atrial activity in close proximity to the anterior limbus of the fossa ovalis. During decremental atrial pacing, the atrial potential exhibited amplitude alternans at a pacing cycle length (CL) of 135 +/- 14 msec. In ten isolated perfused canine hearts, a bipolar electrode catheter was positioned with its tip against the right anterior interatrial septum just superior to the tendon of Todaro. The AV Wenckebach CL (WCL) averaged 262 +/- 21 msec. During further decreases in pacing CL, the bipolar atrial potential developed a 2:1 amplitude alternans (9/10 dogs) at CL = 168 +/- 15 msec and then split into two components with subsequent 2:1 block between these components (10/10 dogs) at CL = 152 +/- 19 msec. Radiofrequency ablation at this site in six dogs prolonged the stimulus to HB interval from 113 +/- 19 to 151 +/- 30 msec (P < 0.01) without changing the WCL, consistent with ablation of the fast AV nodal pathway. In six other isolated perfused canine hearts, an octapolar catheter (2-mm spacing) was positioned along the anterior limbus of the fossa ovalis with the tip electrode located over the anterior portion (apex) of the triangle of Koch. The aforementioned 2:1 amplitude alternans occurred at a longer CL in the distal electrodes located at the tendon of Todaro than in the proximal electrodes at farther distances from the tendon of Todaro (185 +/- 25 vs 171 +/- 20 msec, P < 0.05), as did the 2:1 block between the two components (161 +/- 18 vs 150 +/- 18 msec, P < 0.05). Microelectrode recordings obtained adjacent to the catheter demonstrated 2:1 alternans and block patterns in the action potentials of transitional cells but not in atrial cells, which exhibited 1:1 conduction at all CL. CONCLUSIONS: The transitional cell zone in the anterior interatrial septum exhibits a specific rate-dependent, spatial gradient of conduction block, which can be recorded in bipolar electrograms as well as microelectrode recordings. Electrophysiologic changes induced by radiofrequency ablation of this anterior atrial/transitional cell zone (corroborated by histology) provide strong presumptive evidence that this area constitutes all or a major part of the fast AV nodal pathway.

Animals↗

PubMed1996

Intracellular trafficking of cholesterol monitored with a cyclodextrin.

The sterol binding agent 2-hydroxypropyl-beta-cyclodextrin is shown to be a convenient and useful experimental tool to probe intracellular pathways of cholesterol transport. Biochemical and cytochemical studies reveal that cyclodextrin specifically removes plasma membrane cholesterol. Depletion of plasma membrane sphingomyelin greatly accelerated cyclodextrin-mediated cholesterol removal. Cholesterol arriving at the plasma membrane from lysosomes and the endoplasmic reticulum was also removed by cyclodextrin. Cellular cholesterol esterification linked to the mobilization of cholesterol from lysosomes was strongly attenuated by cyclodextrin, suggesting that the major portion of endocytosed cholesterol is delivered from lysosomes to the endoplasmic reticulum via the plasma membrane. Evidence for translocation of lysosomal cholesterol to the endoplasmic reticulum by a plasma membrane-independent pathway is provided by the finding that cyclodextrin loses its ability to suppress esterification when plasma membrane sphingomyelin is depleted. The Golgi apparatus appears to play an active role in directing the relocation of lysosomal cholesterol to the plasma membrane since brefeldin A also abrogated cyclodextrin-mediated suppression of cholesterol esterification. Using cyclodextrin we further show that attenuated esterification of lysosomal cholesterol in Niemann-Pick C cells reflects defective translocation of cholesterol to the plasma membrane that may be linked to abnormal Golgi trafficking.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1996

Cytotoxicity and membrane damage in vitro by inclusion complexes between gamma-cyclodextrin and siloxanes.

Inclusion complexes of gamma-cyclodextrin and octamethylcyclotetrasiloxane (D4), decamethyltetrasiloxane (M10TS), and 1,3,5,7-tetramethyltetravinylcyclotetra - siloxane (TMTV-D4) were prepared to compare the cytotoxic effects of siloxanes in vitro. In these preparations, the hydrophobic siloxanes are surrounded by a hydrophilic shell of eight circularly linked D-glucose molecules (gamma-cyclodextrin), and upon contact with plasma membranes the siloxane molecule can intercalate into the lipid bilayer of the cell membrane. XRPC24, 2-11 plasmacytoma, CH12.LX lymphoma and P388D1 macrophage-like cells were used as indicator cells in toxicity assays. Using an MTT tetrazolium reduction to formazan test, a colorimetric method to determine the number of viable cells, the 50% minimal lethal doses (CD50) for the siloxane compounds were found to range from 30 to 50 microM. Sublethal doses (e.g., 15 microM and lower) resulted in the loss of lactate dehydrogenase (LDH) and glutathione (GSH) from the cytosolic compartment of the target cells and thus indicated cytotoxicity. Treatment of macrophages with siloxanes resulted in a higher production of interleukin-6 (IL-6) than was exhibited by untreated macrophages. The B9 cell bioassay of these treated cells showed as much as a 10 fold higher production (500 U/ml) of IL-6 than did the untreated cells. The degree of increase was dependent on the compound and concentration used. The results of this study show that low molecular weight siloxanes produce lethal effects on B-lymphocyte derived target cells in vitro and permeabilize the plasma membranes at lower sublethal concentrations.

Animals↗

PubMed1996

Hydroxypropyl cyclodextrins: potential synergism with carcinogens.

The solubility of the lipophilic carcinogens benzo[a]pyrene and aflatoxin B1 in water increases linearly and substantially with the concentration of hydroxypropyl beta-cyclodextrin present. Results of a kinetic study of naphthalene, a model for more potent carcinogens, indicate that the increase in the dissolution rate and in the transport through the aqueous phase into a nonpolar phase is on the same order of magnitude as the increase in solubility. Consequently, hydroxypropyl beta-cyclodextrin, when used in pharmaceutical formulations, has the potential to increase the absorption of carcinogens which enter the gastrointestinal tract either as food components or from air pollution through saliva. Only the above mechanism's simple proportionality needs be considered for estimating the increases in carcinogen absorption in the upper gastrointestinal tract and in the colon. In the presence of bile, however, additional factors are involved and the proportionality does not apply. Bile micelles, which themselves are effective solubilizers of lipophilic carcinogens, were disrupted by hydroxypropyl beta-cyclodextrin because of the formation of complexes with bile salts. Thus, in the presence of bile, two systems for delivery of carcinogens may coexist: that of cotransport with lipids and that of delivery through solubilization by hydroxypropyl beta-cyclodextrin.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1995

Separation of cyclodextrins and their derivatives by thin-layer and preparative column chromatography.

Cyclodextrins, their derivatives and products of their partial hydrolysis are clearly separated by chromatography on silica gel by mobile phases containing aqueous ammonia and organic solvent (acetonitrile or 1-propanol). This system allows separation of compounds with different numbers of substituents on cyclodextrin, but does not allow the separation of isomers; the system can be used both for thin-layer chromatography and for preparative column chromatography. The isomers in the fraction thus obtained can be in some cases separated, after peracetylation, by chromatography on silica gel using a mobile phase consisting of methanol and dichloromethane. This chromatographic sequence potentially yields derivatives of cyclodextrins in quantities which enable evaluation of their solubilization and biological properties.

Acetylation↗

PubMed1995

Regioselectivity of alkylation of cyclomaltoheptaose (beta-cyclodextrin) and synthesis of its mono-2-O-methyl, -ethyl, -allyl, and -propyl derivatives.

Mono-2-O-methyl-, -2-O-ethyl-, and -2-O-allyl-cyclomaltoheptaose were prepared by alkylations of cyclomaltoheptaose in dilute aqueous alkali, and mono-2-O-propylcyclomaltoheptaose was obtained by hydrogenation of the allyl derivative. All the 2-O-alkyl derivatives were less soluble in water than was cyclomaltoheptaose. All formed inclusion complexes with toluene in aqueous solution, but only the methyl ether was less soluble in the water-toluene system than in water. The solubilities of the other ethers in water were enhanced by the addition of toluene. Partial methylation of cyclomaltoheptase with 13C-enriched dimethyl sulfate in dilute aqueous alkali yielded mixtures of products. The substitution patterns were analyzed by GLC-MS of the alditol acetates, prepared by hydrolysis, reduction, and acetylation, and by 13C NMR after complete permethylation with nonenriched reagent. The results showed that methylation at O-2 is a predominant but not an exclusive reaction; as expected, the regioselectivity decreases with increasing degree of methylation.

Alkylation↗

PubMed1995

Safety of parenteral hydroxypropyl beta-cyclodextrin.

Post-treatment data were collected on a patient who received intravenous hydroxypropyl beta-cyclodextrin in a dose of 1.5 g/kg in 1985. Although no untoward effects were observed in this patient, rarely occurring agitation and pulmonary edema have been noted after injections into rabbits and dogs, respectively. These complications are analyzed here on the basis of symptoms and on the effects of hydroxypropyl beta-cyclodextrin on the biochemistry of a representative lipid, cholesterol, which were studied in rats. It is hypothesized that these untoward effects of parenteral hydroxypropyl beta-cyclodextrin are due to complex formation, with lipid mediators of pathological responses, of which prostaglandins are one example. These mediators normally have brief and localized functions; if hydroxypropyl beta-cyclodextrin happens to be injected when these mediator systems are activated, their influence and the responses of the organism may be increased.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1995

Vasoactive intestinal peptide and nerve growth factor effects on nerve regeneration.

Sixty rat sciatic nerves were used to study the effects of vasoactive intestinal peptide (VIP) and nerve growth factor (NGF) on nerve regeneration. They were divided into three groups. Groups 1 and 2 were treated with VIP and NGF, respectively, after dividing the nerves without repair and placing them in silastic chambers. Group 3 served a control. The rate and quality of nerve regeneration were compared among the groups using caliper measurements and histologic evaluation. Both VIP and NGF groups showed an enhanced rate of regeneration at three weeks as compared to controls (p < 0.05). The quality of nerve regeneration histologically and by axonal counting was not significantly different among the three groups, except for the presence of less vascularity in the VIP as compared with the NGF group. In addition to NGF, VIP appears to increase the rate of nerve regeneration as compared to controls.

Animals↗

PubMed1994

Safety of oral cyclodextrins: effects of hydroxypropyl cyclodextrins, cyclodextrin sulfates and cationic cyclodextrins on steroid balance in rats.

Derivatives of beta-cyclodextrin differing in the length of a hydroxyalkyl substituent (CH2CH2OH, CH2CHOHCH3, CH2CHOHCH2CH2CH2CH3) or in the electrical charge of the substituents (SO4-, CH2CHOHCH2N(CH3)3+) and hydroxypropyl derivatives (CH2CHOHCH3) of alpha-, beta-, and gamma-cyclodextrin were compared, individually and in mixtures, as solubilizers of cholesterol. The most effective solubilizer proved to be hydroxypropyl derivatives of beta-cyclodextrin; beta-cyclodextrin sulfate (SO4-) was practically devoid of solubilizing activity. Oral administration of these cyclodextrin derivatives, some of which are both nondegradable and effective complexation agents for cholesterol and bile acids, nevertheless did not affect the conversion of [14C]acetic acid to [14C]-cholesterol in rat under the same conditions when another bile acid complexation agent, cholestyramine, increased that conversion. Thus, complexation of cholesterol and of bile acids by cyclodextrin derivatives, which is a significant and well-defined phenomenon in vitro, seems to have limited importance in terms of excretion of cholesterol from the gastrointestinal tract. It is proposed that various untoward effects observed after chronic large oral doses of hydroxypropyl beta-cyclodextrin are administered are not caused by an increased excretion of some vital lipophile or enzyme but are probably caused by solubilization and increased absorption of toxic contaminants of the ingested food.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1994

Parenteral hydroxypropyl cyclodextrins: intravenous and intracerebral administration of lipophiles.

Hydroxypropyl cyclodextrins are nontoxic carbohydrate derivatives of moderate molecular weight (1030-1750 Da) which form water-soluble complexes with many lipophiles. The fate of hydroxypropyl beta-cyclodextrin alone and in complex with testosterone or cholesterol injected intravenously or intracerebrally into rats was followed. More than 90% of intravenously administered hydroxypropyl beta-cyclodextrin was cleared into urine in 4 h, as previously described (Monbaliu, J.; Van Beijsterveld, L.; Meuldermans, W.; Szathmary, S.; Haykants, J. Abstracts, 5th International Symposium on Cyclodextrins, Paris, 1990; Abstract 65). After the injection of steroids in complex with hydroxypropyl beta-cyclodextrin into the tail vein of rats, the steroid component was released from the complex, before it reached the kidneys; the release occurred mainly into the proteins and lipoproteins of serum. Hydroxypropyl beta-cyclodextrins injected alone into the brain were cleared within less than 24 h, presumably via the flow of interstitial and cerebrospinal fluids, and eventually were excreted in urine. Testosterone, incorporated in a hydroxypropyl beta-cyclodextrin complex, after intracerebral injection was cleared from the brain even more rapidly than hydroxypropyl beta-cyclodextrin, presumably by crossing the blood-brain barrier and later removal to the liver by the specific carrier proteins in serum. Complexed cholesterol, in a similar experiment, was largely retained in the brain and its distribution there was uneven and remained that way for at least 3 days. It is clear that lipophilic agents, after their incorporation into hydroxypropyl beta-cyclodextrin complexes and subsequent in vivo administration, are rapidly released and exchanged into the plasma. In absence of plasma they enter tissues surrounding the injection site and thus are also promptly transferred into the organism's lipid systems. The manner in which different lipophilic agents are transported in vivo appears not to be greatly affected by their previous complexation; rather hydroxypropyl cyclodextrins just enable their entry in a larger amount and in an exchangeable, nonaggregated form.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1994

Endocrine interactions: adrenal steroids and precursors.

Adult male rats (n = 48) were castrated and treated daily for 4 wk with adrenal steroids in the presence or absence of adjuvant testosterone. Dehydroepiandrosterone (DHEA), DHEA sulfate, and androstenedione (2 mg/kg body wt) were administered as cyclodextrin complexes to mimic the pharmacodynamics of the endogenous products. Although they are the substrates for testosterone synthesis in target tissues, supplements of adrenal steroids alone were unable to maintain integrity of sociosexual responses and androgen target tissues after castration. More surprising, groups administered adrenal precursor plus testosterone showed substantial suppression of the typical restoration of reproductive systems in castrates receiving androgen therapy. The adrenal steroids, however, were not functionally identical. Each steroid interacted with testosterone to leave its own distinctive "footprint" on androgen-sensitive systems. The conclusion is that the endogenous adrenal products are not simply passive precursors of testosterone. Adrenal steroids may serve as endocrine regulators of androgen bioavailability and bioactivity.

Adrenal Glands↗

PubMed1994

Epithelioid cell histiocytoma. A report of 10 cases including a new cellular variant.

Epithelioid cell histiocytoma is a recently recognized lesion that is considered to be a variant of cutaneous fibrous histiocytoma (dermatofibroma). Ten cases are presented, including their light microscopic, immunohistochemical, and ultrastructural features. Eight of the cases are similar to those previously reported, presenting as elevated nodules arising on the extremities and composed of epithelioid histiocytes with overlying epidermal effacement. Two of the cases were composed of cells with the same morphologic and immunohistochemical characteristics as typical epithelioid cell histiocytoma, including factor XIIIa positivity, but these arose in the reticular dermis and exhibited prominent cellularity.

Adult↗

PubMed1993

Crystal structure of 6-O-[(R)-2-hydroxypropyl]cyclomaltoheptaose and 6-O-[(S)-2-hydroxypropyl]cyclomaltoheptaose.

Crystal structures of 6-O-[(R)-2-hydroxypropyl]- and 6-O-[(S)-2-hydroxypropyl]-cyclomaltoheptaose were determined by X-ray analysis. In both structures, the 2-hydroxypropyl group is inserted into the macrocyclic cavity of the next molecule related by the two-fold screw axis, and a helically extended polymeric structure is formed by repetition of the intermolecular inclusion. The hydroxyl group of the substituent group penetrates through the macrocyclic ring from the secondary hydroxyl side and is linked to an HO-6 group by a hydrogen bond. Comparison of intermolecular contacts of the substituent group indicates that the (S)-2-hydroxypropyl group is better fitted to the cavity than the (R)-2-hydroxy-propyl group.

Carbohydrate Conformation↗