Hydrogen Abstraction by Alkoxyl Radicals: Computational Studies of Thermodynamic and Polarity Effects on Reactivities and Selectivities

Density functional theory calculations (ωB97X-D) are reported for the reactions of methoxy, tert-butoxy, trichloroethoxy, and trifluoroethoxy radicals with a series of 26 C-H bonds in different environments characteristic of a variety of hydrocarbons and substituted derivatives. The variations in activation barriers are analyzed with modified Evans-Polanyi treatments to account for polarity and unsaturation effects. The treatments by Roberts and Steel and by Mayer have inspired the development of a simple treatment involving the thermodynamics of reactions, the difference between the reactant radical and product radical electronegativities, and the absence or presence of α-unsaturation. The three-parameter equation (ΔH^⧧ = 0.52ΔH_rxn(1 - d) - 0.35Δχ_AB² + 10.0, where d = 0.44 when there is α-unsaturation to the reacting C-H bond), correlates well with quantum mechanically computed barriers and shows the quantitative importance of the thermodynamics of reactions (dictated by the reactant and the product bond dissociation energies) and polar effects.

Systemic lupus erythematosus presenting as erythema annulare centrifugum

A case of systemic lupus erythematosus presenting as erythema annulare centrifugum involving atypical sites (face, palm and sole) and raised serum angiotensin-converting enzyme levels has been illustrated.

Spindle cell lipoma masquerading as lipomatous pleomorphic adenoma: A diagnostic dilemma on fine needle aspiration cytology

Spindle cell lipoma is a relatively uncommon benign adipocytic tumor that usually presents in subcutaneous fat of adult men. These are a rare form of lipoma, accounting for 1.5% of all lipomatous tumors, with a low rate of local recurrence and no risk of malignant behavior/dedifferentiation. Although few studies addressing the histological findings of spindle cell lipoma have been described, only a few descriptions of fine needle aspiration cytology (FNAC) findings have been documented in literature. We present a case of a 55-year-old male with a nodular swelling over left cheek (in the parotid region), which due to its location as well as prominent myxoid background prompted us to include the lipomatous salivary gland lesions in differential diagnosis. Our objective is to document and delineate the characteristic cytological features of spindle cell lipoma, which may permit a confident diagnosis on FNAC smears.

Inclusion adducts of 4,4-bis(4'-biphenylyl)cyclohexa-2,5-dienone: a clay mimic organic host

In the lamellar architecture of the title crystal structure mediated by C-H...O hydrogen bonds, 1,2-dimethoxyethane and n-hexane are included in the hydrophobic galleries; isostructurality of these clathrates is a unique case of guest mimicry.

Finishing occlusion in Class II or Class III molar relation: therapeutic Class II and III

The most frequent extraction regime consists of the removal of upper and lower premolars. Depending on anchorage requirements, camouflage treatment options, surgical intervention, or the absence of teeth in only one arch, it may become necessary to finalize the occlusion with a one-dental-unit discrepancy between the upper and lower dental arches. Guidelines are presented for finishing occlusions in Class II or Class III molar relation.

N-(4-Biphenylyl)urea

In the crystal structure of the title compound, C13H12N2O, N-H(anti)...O hydrogen bonds produce the so-called urea alpha-network and the N-H(syn) donor forms an unconventional N-H...pi hydrogen bond.

Malakoplakia of bone. A case report

BACKGROUND

Malakoplakia is an uncommon but distinctive granulomatous disease, characterized by an accumulation of histiocytes or Von Hansemann cells containing intracytoplasmic, laminated Michaelis-Gutmann bodies.

CASE

A 3-year-old male presented with a tender swelling in the left gluteal region that had been present for one month. Smears made from a fine needle aspirate showed large histiocytic cells containing intracytoplasmic, basophilic, laminated, targetoid Michaelis-Gutmann bodies resembling Von Hansemann cells in malakoplakia. Histopathology confirmed the diagnosis of malakoplakia of bone.

CONCLUSION

This case, histologically proven to be malakoplakia, demonstrated regression of the lesion following therapy. The characteristic cytologic features and presence of Von Hansemann cells may in themselves be diagnostic and obviate the need for biopsy.

Leiomyosarcoma of the mesocolon--a case report

Retroperitoneal leiomyosarcomas including those arising from the mesentery are rare. These account for 5.8% of all soft tissue sarcomas. Most of these tumors present in late life with female preponderance. Diagnosing these tumors at an early stage is difficult due to their location. Hence, most of them attain large sizes with metastases to distant sites at the time of diagnosis. We report a case of leiomyosarcoma arising from the sigmoid mesocolon due to it's rarity and unusual clinical presentation.

Lichen Planus-a Clinico-histopathological

The clinico-histopathological features of 75 patients of lichen planus were studied. The male to female ratio was 1:13. The largest number of patients (30.6%) fell into the 31-40 year age group. Two patients had systemic hypertension. There was no history of lichen planus in the family. All patients presented with severe itching within 1-2 months of onset. Papular lesions were seen in 72% and papules with plaques were seen 16%. Lower limbs were involved in 38% of cases. Mucosal involvement was seen in 24% in addition to skin involvement ; nail involvement hypertrophicus (17.3%). Lichen planopilaris and oral lichen planus were uncommon. Clinico-histopathological discrepancies were observed in 7 patients. Civatte bodies were seen in only 37% of cases.

[Tris(4-tolyl)methyl]benzene

The crystal structure of the title compound, C(28)H(26), in the monoclinic space group C2/c has a columnar packing arrangement with a 7.20 A axis, a feature common to several tetraphenylmethanes.

Crystal chemistry of some synthetic 2-oxa-steroids: conformation, packing motifs and isostructurality

The crystal structures of six synthetic 2-oxa-steroids (A-ring lactone steroids) have been determined by single-crystal X-ray diffraction. The conformation and hydrogen bonding in these oxa-steroids is compared with packing motifs in the natural steroids and the anabolic agent, Anavar. O-H...O hydrogen bonding with lactone carbonyl O is the preferred arrangement in molecules with a C-OH group. The donor H atoms of A, B and D rings participate in C-H...O interactions with lactone carbonyl O and D-ring hydroxyl/ketone O acceptor atoms. The conformation of the lactone ring in these analogues is different from the natural androgens because replacement of the C2-methylene group by an O atom changes the geometry of the A ring. Two structurally related lactone steroids provide the first example of O-H...O/C-H...O interaction mimicry and furthermore the two components form a binary solid solution. The O-H...O and C-H...O hydrogen bonds in 2-oxa-steroid crystal structures are analysed and the observed preferences discussed in terms of geometric and chemical factors.

Localized tenosynovial giant cell tumor of tendon sheath. A case report

BACKGROUND

Localized tenosynovial giant cell tumor of tendon sheath (TGCT-L) is a benign, slowly growing lesion with a peak incidence in the third to fifth decade of life. It is thought to arise from the synovium of tendon sheaths, frequently affecting interphalangeal joints of the hands, feet, ankles and knees. Although the histopathologic appearances are well established, only a few reports describe the cytomorphology of this lesion.

CASE

A 37-year-old female presented with a slowly growing, nontender mass located near the left ankle joint. The cytologic features of localized tenosynovial giant cell tumor of tendon sheath (TGCT-L) include abundant mononuclear histiocytic cells occurring singly and in three-dimensional tissue fragments, hemosiderin within histiocytes and a few multinucleated giant cells. Subsequently, the histopathologic examination of the surgical specimen was proven to be TGCT-L.

CONCLUSION

Fine needle aspiration cytology can be used as a diagnostic tool for early and accurate detection of TGCT-L since the cytologic features combined with clinical details are sufficiently distinctive.

An immunopathological study of lichen planus

Twenty-five patients with clinically diagnosed lichen planus were examined for direct immunofluorescence patterns in biopsies. The male to female ratio was 1:1.77. The peak incidence was observed in 11-20 years age group. Most (96%) of the patients presented with moderate to severe itching within two months of onset of symptoms. Sixty percent of the patients had violaceous papules; 20% had both papules and plaques. Simultaneous oral involvement was seen in 4% of cases; 8% showed nail changes. Thirteen patients had classical LP, 9 had lichen planus hypertrophicus, 2 had lichen planus actinicus, and one had lichen planopilaris. Direct immunofluorescence revealed fibrin deposition in 64% of cases as a linear pattern at dermo-epidermal junction, as coarse granular deposits of IgM sub-epidermally in 24 of cases and at the dermo-epidermal junction as C 3 in20% of cases. Civatte bodies were seen in 5 cases with H&E staining, but direct immunofluorescence for IgM, fibrin and C 3 was observed only in two cases. This suggests activation of complement and fibrinogen cascade. Whether this is the cause or effect of pathological processes in lichen planus remains to be determined.

Idiopathic priapism

Idiopathic priapism is rarely seen in children. Two children with idiopathic priapism are presented, followed by a detailed discussion of priapism. Particular attention is paid to idiopathic priapism. Additionally, an algorithm for diagnosing and managing children presenting with priapism is presented.

Malignant histiocytosis in childhood: A case report

A case of malignant histiocytosis (MH) in a 12-year-old male child is described. Fever and wasting were the most prominent symptoms. Bilateral cervical and axillary lymphadenopathy was present along with hepatosplenomegaly. The haematological, cytological and histopathological features are described. The diagnostic dilemma presented during the diagnosis of this case is also discussed. Diagn. Cytopathol. 1999;21:359-361.

Advantages and risks of ileovesicostomy for the management of neuropathic bladder

OBJECTIVES

To evaluate the efficacy and complications of ileovesicostomy in patients with neurogenic bladder dysfunction.

METHODS

Fifteen consecutive neurologically impaired patients (8 from multiple sclerosis, 4 from spinal cord injury, 3 from other causes) with complications of previous bladder management underwent ileovesicostomy. There were 10 women and 5 men. All patients were either poor candidates for or refused continent urinary diversion or bladder augmentation cystoplasty.

RESULTS

At a mean follow-up of 23.2 months, 14 of 15 patients had low-pressure urine drainage through their ileovesicostomy. Four women with documented preoperative detrusor hyperreflexia had postoperative intermittent mild urge incontinence per native urethra. They did not require any further treatment, except for oral anticholinergic drugs (oxybutynin and tolterodine). Because of persistent severe urge incontinence, 1 woman required conversion of her ileovesicostomy to an ileal conduit with concurrent cystectomy. The ileovesicostomy of another myelodysplastic man who had four failed artificial urinary sphincters in the past was also converted to an ileal conduit because of persistent urethroperineal fistula despite perineal urethral closure. Renal function was preserved in all patients. Long-term complications were stomal stenosis in 2 patients, bladder and kidney stone formation in 5, and symptomatic urinary tract infections in 3.

CONCLUSIONS

Ileovesicostomy can be safely performed in neurologically impaired women and men. Severe preoperative detrusor hyperreflexia with urge incontinence appears to be a risk factor for persistent urge incontinence postoperatively in women. Continued routine urologic surveillance for infection and stones is mandatory. Ileovesicostomy is a versatile procedure for neurologically impaired patients, because it can be converted to a conventional ileal conduit if necessary. In addition, in cases of neural recovery, the ileal "chimney" can be excised and the patient's original lower urinary tract would be preserved.

Prostatic carcinoma with signet ring cells: a clinicopathologic and immunohistochemical analysis of 12 cases, with review of the literature

Prostatic adenocarcinoma with a signet ring cell (SRC) component is a rare, incompletely characterized variant that must be distinguished from similar tumors of bladder or gastric origin. In this study, we used mucin and immunoperoxidase stains on formalin-fixed, paraffin-embedded sections from 12 prostatic adenocarcinomas with SRC components, with antibodies to prostate-specific antigen (PSA), cytokeratins, MIB-1, bcl-2, c-MET, CD44v6, and CD44v7; we performed a comparison study on six bladder and seven gastric carcinomas with SRCs. The prostatic SRC component was always associated with the usual high-grade adenocarcinoma. Both components were positive for PSA, AE1/AE3, and CAM 5.2 (12 cases of 12) and also expressed c-MET (5 cases of 9), CD44v6 (9 of 10), and CDv7 (9 of 10). Only rare cells stained for bcl-2 (3 cases of 9). The mean MIB-1 proliferation index was 8%. Intracellular mucin was identified (periodic acid-Schiff with diastase predigestion (PAS-D) in 9 cases of 10, mucicarmine in 5 of 10, alcian blue in 6 of 10). Bladder and gastric tumors were positive for PSA (3 cases of 6 and 2 of 7, respectively), using a polyclonal antibody, and for bcl-2 (5 cases of 6, 2 of 7), c-MET (6 of 6, 6 of 7), CD44v6 (5 of 6, 6 of 7), and CD44v7 (4 of 6, 4 of 7), with mean MIB-1 proliferation indices of 15 and 35%, respectively. All were negative for cytokeratin 34 beta E12. We conclude that prostatic adenocarcinomas with SRC components are typically accompanied by high-grade adenocarcinoma; are variably positive for mucin, with PAS-D being the most sensitive stain; show expression of PSA, cytokeratins, MIB-1, bcl-2, c-MET, and CD44 similar to that shown by high-grade adenocarcinoma components; have a low MIB-1 proliferation index; and are not always distinguishable from SRC components of bladder and stomach carcinomas with any of the above stains, including PSA.

Use of NMR imaging in the optimization of a compression-coated regulated release system

Nuclear magnetic resonance (NMR) imaging is routinely used to detect the protons of mobile water molecules within samples. In this investigation, this non-destructive, non-invasive technique was used to determine the cause for faster than predicted drug release from a dissolution-based regulated-release tablet. The NMR images of tablets, from two different formulations, taken at various intervals of time while immersed in static USP dissolution medium showed that the tablet with faster than predicted drug release had a porous coating. The porous coat exposed more of the core surface area to the dissolution medium than desired and this caused an increase in the rate of dissolution of the core. The data presented in this paper demonstrate the usefulness of NMR imaging in solid dosage form development.

Trimethyl isocyanurate and triethyl isocyanurate

The crystal structures of trimethyl isocyanurate, C6H9N3O3, (1), and triethyl isocyanurate, C9H15N3O3, (2), contain topologically similar C--H...O hydrogen-bonded networks. In (1), there are two symmetry-independent molecules and each forms its own layer structure. In (2), two of the ethyl groups point one way with respect to the heterocyclic ring, while the third points in the opposite direction.

High dissociation constants (pKa) of basic permeants are associated with in vivo skin irritation in man

Previously, we have investigated the relationship between dissociation constant (pKa) and skin irritation potential. In the present experiment, 12 basic compounds, with varying pKa values ranging from 1.4 to 11.2, were applied on the backs of 12 healthy adult panellists. Cutaneous reactions were measured objectively, using reflectance spectroscopy and transepidermal water loss (TEWL), and evaluated subjectively with a modified Draize scale. A positive correlation between increasing pKa and skin irritation capacity, measured either visually or by reflectance spectroscopy, was found, but only mecamylamine (pKa = 11.2) induced a significant increase in transepidermal water loss. Compounds with low pKa also induced a paradoxical vasoconstriction measured by reflectance spectroscopy. Only high pKa appeared predictive of in vivo skin irritation, and these chemicals apparently induce skin irritation with only minimal disruption of the skin barrier. A simple 1-variable model is predictive of skin irritation for this series of organic permeants with increasing pKa.

Influence of skin irritants on percutaneous absorption

The effects of the application of skin irritants on the in vitro percutaneous absorption of three model compounds of diverse physico-chemical properties, caffeine, indomethacin, and hydrocortisone, were investigated. Norephedrine and imipramine, basic drugs with a known skin irritation potential, were employed to damage the skin. Treatment with norephedrine increased the permeation of caffeine and hydrocortisone by two- to fourfold, while absorption of indomethacin declined an order of magnitude. A similar result was obtained for the effect of treatment with imipramine on transport of caffeine. Pretreatment with imipramine promoted hydrocortisone absorption 10-fold but, unlike norephedrine, did not alter indomethacin permeation. While both treatments in vivo caused an increase (norephedrine > imipramine) in the pH on the surface of skin and after tape-stripping the skin, only norephedrine caused changes in transepidermal water loss in vivo in man. Since imipramine was the more severe irritant as judged by erythema, alterations by irritants of barrier function appeared rather complex.

Gastrin-dependent inhibitory effects of octreotide on the genesis of gastric ECLomas

BACKGROUND

The efficacy of octreotide in the regulation of endocrine tumor secretion and symptomatology has been well documented. Its effects on neuroendocrine tumor generation and cell proliferation are less well understood. The purpose of this study was to determine if blockade of somatostatin receptors by octreotide would alter gastrin levels and influence enterochromaffin-like (ECL) cell proliferation.

METHODS

The well-established gastric ECLoma model of the rodent, mastomys, was used. Animals received loxtidine (1 mg/kg/day), an irreversible H2 blocker, and subcutaneous slow release, octreotide pellet implants (150 or 300 micrograms/kg/day) or placebo pellets for a 4-month period.

RESULTS

Control parameters for gastric mucosal thickness, plasma gastrin level, ECL cell density, and bromodeoxyuridine-positive cells were 517 +/- 20 microns, 46.1 +/- 11.4 pmol/L, 7.4 +/- 0.9 cells/visual field, and 13.8 +/- 2.6 cells/visual field, respectively. After loxtidine-placebo treatment all values were significantly increased (p < 0.05; 883 +/- 70 microns, 192.8 +/- 10.6 pmol/L, 97 +/- 16.2 cells/visual field, and 51.7 +/- 19.2 cells/visual field, respectively). High dose octreotide significantly inhibited all parameters (668 +/- 3.5 microns, 66.2 +/- 20.5 pmol/L, 37.0 +/- 8.0 cells/visual field, and 10.9 +/- 2.2 cells/visual field; p < 0.05). Low dose octreotide failed to significantly inhibit ECL cell density mucosal thickness, or cell proliferation.

CONCLUSIONS

Irreversible H2 receptor blockade results in hypergastrinemia and ECL cell tumor generation. Hypergastrinemia, ECL cell hyperplasia, and cell proliferation are significantly inhibited by in vivo blockade of somatostatin receptors by administration of octreotide.