[Necrotizing ulcerative diseases in military population].

Necrotizing ulcerative diseases were prevalent in military personnel throughout history. Nowadays, its prevalence declined substantially in industrialized countries. Studies among immunocompromised patients suggest it is still a reason for concern among this population. We present two cases diagnosed and treated at our department. It seems that necrotizing ulcerative diseases are still a relevant entity in the Israeli Defense forces therefore it is of great importance to conduct proper diagnosis, treatment and follow up of the patients.

Direct, catalytic monofluorination of sp³ C-H bonds: a radical-based mechanism with ionic selectivity.

Recently, our group unveiled a system in which an unusual interplay between copper(I) and Selectfluor effects mild, catalytic sp(3) C-H fluorination. Herein, we report a detailed reaction mechanism based on exhaustive EPR, (19)F NMR, UV-vis, electrochemical, kinetic, synthetic, and computational studies that, to our surprise, was revealed to be a radical chain mechanism in which copper acts as an initiator. Furthermore, we offer an explanation for the notable but curious preference for monofluorination by ascribing an ionic character to the transition state.

The Evolution of Compact Binary Star Systems.

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Mergings of compact-star binaries are expected to be the most important sources for forthcoming gravitational-wave (GW) astronomy. In the first part of the review, we discuss observational manifestations of close binaries with NS and/or BH components and their merger rate, crucial points in the formation and evolution of compact stars in binary systems, including the treatment of the natal kicks, which NSs and BHs acquire during the core collapse of massive stars and the common envelope phase of binary evolution, which are most relevant to the merging rates of NS-NS, NS-BH and BH-BH binaries. The second part of the review is devoted mainly to the formation and evolution of binary WDs and their observational manifestations, including their role as progenitors of cosmologically-important thermonuclear SN Ia. We also consider AM CVn-stars, which are thought to be the best verification binary GW sources for future low-frequency GW space interferometers.

Nanoparticles of N-Vinylpyrrolidone Amphiphilic Copolymers and Pheophorbide a as Promising Photosensitizers for Photodynamic Therapy: Design, Properties and In Vitro Phototoxic Activity.

A series of nanoparticles (NPs) with a hydrodynamic radius from 20 to 100 nm in PBS was developed over the solubilization of hydrophobic dye methyl pheophorbide a (chlorin e6 derivative) by amphiphilic copolymers of N-vinylpyrrolidone with (di)methacrylates. Photophysical properties and biological activity of the NPs aqueous solution were studied. It was found that the dye encapsulated in the copolymers is in an aggregated state. However, its aggregation degree decreases sharply, and singlet oxygen quantum yield and the fluorescence signal increase upon the interaction of these NPs with model biological membranes-liposomes or components of a tissue homogenate. The phototoxic effect of NPs in HeLa cells exceeds by 1.5-2 times that of the reference dye chlorin e6 trisodium salt-one of the most effective photosensitizers used in clinical practice. It could be explained by the effective release of the hydrophobic photosensitizer from the NPs into biological structures. The demonstrated approach can be used not only for the encapsulation of hydrophobic photosensitizers for PDT but also for other drugs, and N-vinylpyrrolidone amphiphilic copolymers show promising potential as a modern platform for the design of targeted delivery vehicles.

The May threshold and life-history allometry.

One of Robert May's classic results was finding that population dynamics become chaotic when the average lifetime rate of reproduction exceeds a certain value. Populations whose reproductive rates exceed this May threshold probably become extinct. The May threshold in each case depends upon the shape of the density-dependence curve, which differs among models of population growth. However, species of different sizes and generation times that share a roughly similar density-dependence curve will also share a similar May threshold. Here, we argue that this fact predicts a striking allometric regularity among animal taxa: lifetime reproductive rate should be roughly independent of body size. Such independence has been observed in diverse taxa, but has usually been ascribed to a fortuitous combination of physiologically based life-history allometries. We suggest, instead, that the ecological elimination of unstable populations within groups that share a value of the May threshold is a likely cause of this allometry.

Fetal rat intestinal absorption of horseradish peroxidase from swallowed amniotic fluid.

Horseradish peroxidase (HRP) injected into amniotic fluid is swallowed by rat fetuses and within 3-6 h reaches the gut lumen. This macromolecular protein is then absorbed by the columnar lining cells via a system of apical cytoplasmic tubules formed by invaginations of the plasma membrane. From cytoplasm subjacent to the brush border HRP is transported, within vacuoles, to the supranuclear region, where some is retained for at least 18 h, and to interepithelial spaces. Extracellular enzyme is then found throughout the epithelial basement membrane and between connective tissue cells of the mucosal and submucosal layers Finally, HRP can be detected within lumina of blood and lymphatic capillaries, strongly suggesting that it is transported from the intestine to the circulation.

Protein absorption by the intestine of the fetal rat in utero.

Horseradish peroxidase (molecular weight, about 40,000) injected into the amniotic sacs in pregnant rats has been identified ultrastructurally, 6 to 18 hours later, within the fetal intestine in the absorptive cells and the underlying vascular endothelium. This indicates that macromolecular protein within amniotic fluid swallowed by the fetus can be absorbed and transported by fetal intestine, and may indicate that physiological compounds can be transported by this enteric route to contribute to fetal development.

Pathogen population structure can explain hospital outbreaks.

Hospitalized patients are at risk for increased length of stay, illness, or death due to hospital acquired infections. The majority of hospital transmission models describe dynamics on the level of the host rather than on the level of the pathogens themselves. Accordingly, epidemiologists often cannot complete transmission chains without direct evidence of either host-host contact or a large reservoir population. Here, we propose an ecology-based model to explain the transmission of pathogens in hospitals. The model is based upon metapopulation biology, which describes a group of interacting localized populations and island biogeography, which provides a basis for how pathogens may be moving between locales. Computational simulation trials are used to assess the applicability of the model. Results indicate that pathogens survive for extended periods without the need for large reservoirs by living in localized ephemeral populations while continuously transmitting pathogens to new seed populations. Computational simulations show small populations spending significant portions of time at sizes too small to be detected by most surveillance protocols and that the number and type of these ephemeral populations enable the overall pathogen population to be sustained. By modeling hospital pathogens as a metapopulation, many observations characteristic of hospital acquired infection outbreaks for which there has previously been no sufficient biological explanation, including how and why empirically successful interventions work, can now be accounted for using population dynamic hypotheses. Epidemiological links between temporally isolated outbreaks are explained via pathogen population dynamics and potential outbreak intervention targets are identified.

Pathogenesis of rat colon carcinomas induced by N-methyl-N-nitrosourea.

Colon specimens were obtained from 45 young male and female inbred CDF rats between 11 and 42 weeks after they began to receive intrarectal injections of the carcinogen N-methyl-N-nitrosourea (MNU) 43--108 mg, total dose); specimens were also obtained from 26 control rats. Well-developed tumors from rats receiving MNU generally presented grossly as polyps; histologically, as invasive adenocarcinomas that had not metastasized. These tumors resembled their human counterparts. Focal epithelial atypias were found in grossly normal mucosa both from rats that had not yet developed tumors and from tumor-bearing rats. Such foci typically consisted of low columnar cells with enlarged nuclei, increased number of mitoses, cytoplasmic basophilia, and reduced cytoplasmic mucus. Serial section studies of minute foci of atypia indicated that some of them arose from normal deep crypt cells. Transitions were frequently found between atypical foci and in situ or invasive carcinomas. Less commonly, adenomatous epithelium was identified in the early lesions or within the frank adenocarcinomas. It was concluded that most invasive carcinomas in this rat model originate in foci of epithelial atypia, which are found with increasing frequency in the flat mucosa during treatment with MNU, but that some carcinomas also arise from adenomatous epithelium.

Relationship of polyps to cancer of the large intestine.

BACKGROUND: Pathologic and epidemiologic evidence indicates that patients with sporadic (nonfamilial) adenomatous polyps of the large intestine are at high risk of developing colorectal cancer. PURPOSE: Our primary goal in this study was to evaluate the colorectal cancer mortality rate among persons who have had a histologically confirmed benign colorectal polyp. METHODS: We used the retrospective follow-up method to evaluate the risk of death from colorectal cancer in 2872 Rhode Island men and women who were 24 through 79 years of age at the time of surgery for benign polyps in the years 1959 through 1975. RESULTS: Among 2872 subjects, the mortality from colorectal cancer, standardized for age, sex, and calendar time, was estimated as 1.74 (95% confidence interval = 1.44-2.09) times the rate in the general population of Rhode Island residents. Colorectal cancer mortality was higher in the first 5 years of follow-up than it was later. There was little relationship between the numbers of polyps and colorectal cancer mortality, and there was only a modest association between the size of polyps and mortality. Colorectal cancer mortality was more than twice as high in subjects whose polyps were proximal to the sigmoid compared with those with sigmoid or rectal polyps. The observed elevation of risk of colorectal cancer was almost entirely confined to subjects who had an adenomatous polyp. The risk increased strongly with the percentage of villous features in the polyp and was about twice as high in subjects with villous adenoma than in those with other adenomatous polyps. CONCLUSIONS: Our results support the suspected relationship between colorectal polyps and cancer incidence and extend the association to colorectal cancer mortality.

The Evolution of Compact Binary Star Systems.

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars - compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.

Chain Dynamics, Relaxation Times, and Conductivities of Bithiophene--Acene Copolymers Measured Using High Frequency Saturation Transfer EPR.

We present a study to probe the formation of localized aromatic sextets and their effects on the charge transport properties in polymers with acene cores. Bithiophene-acene copolymers containing benzene, naphthalene, or anthracene as acene cores were synthesized using Yamamoto polymerization. Drop-casted polymer films were chemically doped and analyzed using high frequency saturation transfer EPR (HF ST-EPR), a method which has proven useful in the study of conducting polymers. The spin-spin and spin-lattice relaxation times were determined for these polymers at low temperatures (4 to 20 K) and used to obtain inter- and intrachain spin diffusion rates and conductivities. Similar interchain spin diffusion rates were seen across all polymer systems; however, anthracene containing polymer poly(hexylTTATT) was found to have the largest intrachain spin diffusion rate. The poly(hexylTTATT) intrachain spin diffusion rate may be artificially high if the anthracene ring restricts the diffusion of spin to the hexylated quaterthiophene segment in poly(hexylTTATT) whereas the spins diffuse through the acene cores in the benzene and naphthalene derivatives. Alternatively, as both the spin diffusion rates and conductivities vary unpredictably with temperature, it is possible that the π-electron localization previously seen in the anthracene core could be relieved at lower temperatures.

Selection on stability across ecological scales.

Much of the focus in evolutionary biology has been on the adaptive differentiation among organisms. It is equally important to understand the processes that result in similarities of structure among systems. Here, we discuss examples of similarities occurring at different ecological scales, from predator-prey relations (attack rates and handling times) through communities (food-web structures) to ecosystem properties. Selection among systemic configurations or patterns that differ in their intrinsic stability should lead generally to increased representation of relatively stable structures. Such nonadaptive, but selective processes that shape ecological communities offer an enticing mechanism for generating widely observed similarities, and have sparked new interest in stability properties. This nonadaptive systemic selection operates not in opposition to, but in parallel with, adaptive evolution.

Peritumoral and nodal muciphages.

Three patients who underwent surgery for cancer showed Alcian blue positive cells in the sinusoids of the regional lymph nodes and, in one case, extensive infiltration in the soft tissues around the tumor. The cells contained variably sized vacuoles that occasionally indented the nuclei, imparting a signet-ringlike appearance. They were interpreted as muciphages based on morphology, reactivity with mucin stains, positive immunohistochemical staining for KP-1 and Mac-387, and negative staining for cytokeratin, S-100, and leukocyte common antigen (LCA). The material contained in these cells was Alcian blue positive at pH 2.5 and pH 1, and was strongly periodic acid-Schiff positive after diastase digestion. Hyaluronidase only slightly reduced the intensity of the Alcian blue stain. These results indicate that the bulk of the material was epithelial-type mucin. To our knowledge, this is the first report of muciphages in lymph nodes. Careful attention to morphology and immunohistochemical findings is necessary to avoid confusion with metastatic or infiltrating signet ring or mucinous adenocarcinoma.

Colonic oligosaccharide structures deduced from lectin-binding studies before and after desialylation.

Dolichos biflorus agglutinin (DBA) binds N-acetylgalactosamine (GalNAc), and peanut agglutinin (PNA) binds Gal beta(1-3)GalNAc residues (Gal = galactose). We used these lectins with neuraminidase to probe colonic oligosaccharides. Tissues included normal epithelium, adenocarcinomas (T) with contiguous transitional (TM) and normal mucosae (RM), and adenomatous polyps. Except for DBA binding in carcinomas, neuraminidase digestion increased DBA and PNA binding in all epithelia. In untreated specimens, reciprocal gradients for binding by DBA (T less than TM and TM less than RM) and PNA (T greater than TM and T greater than RM) were seen. After neuraminidase, all gradients were abolished except for T less than TM and T less than RM with DBA. We conclude that (1) qualitative as well as quantitative differences may exist between the mucins of benign and neoplastic colonic epithelium, (2) the NeuAc-GalNAc dimer is a widely prevalent terminal oligosaccharide in benign epithelium at all stages of differentiation (NeuAc = sialic acid), and (3) in contrast with evidence from recent biochemical studies, the Gal beta(1-3)GalNAc dimer is a common masked oligosaccharide in benign epithelium.

Histochemical and morphologic studies of mucosa bordering rectosigmoid carcinomas: comparisons with normal, diseased, and malignant colonic epithelium.

Surgically obtained rectosigmoid mucosa ("transitional" mucosa, TM) adjacent to eight primary carcinomas was compared with diseased mucosa (DM) from eight patients without primary carcinoma and mucosa from two normal control subjects by mucin histochemical and morphologic techniques. No differences were found between TM and DM that might have suggested premalignant changes unique to TM. An excess of sialidase-susceptible sialomucins was found in both TM and DM, as was loss of the sulfomucin-sialomucin gradient usually found between normal crypts and surface cells. Increased sialic acid in TM and DM may represent a nonspecific response to injury or inflammation and has been found in other epithelia under similar circumstances. Sialidase also induced substantial reduction of periodic acid-Schiff (PAS) staining, probably due to loss of sialic acid since no other sugars were released during sialidase digestion, as determined by thin-layer chromatography analysis of post-digestion supernatants. Carcinomas generally showed more staining with PAS than with basic dyes; PAS staining was minimally reduced by diastase and sialidase but markedly reduced by phenylhydrazine interposition, suggesting that some type of neutral glycoprotein was responsible. Finally, it was found that overreliance on the high-iron diamine-Alcian blue technique as a single procedure is unwise; this procedure should be accompanied by the use of singly applied dyes, especially high-iron diamine, together with other enzymatic and staining procedures.

Histologic and morphometric study of chronic gastritis in alcoholic patients.

The effect of chronic alcohol ingestion on the gastric mucosa was determined in 96 patients in whom gastroscopy was performed because of upper gastrointestinal symptoms. Seventy-two patients were classified as alcoholics and 24 patients as nonalcoholics. In all cases biopsy specimens were taken from the fundus and antrum. The diagnoses of chronic superficial and atrophic gastritis were based on conventional histologic criteria and a morphometric technique utilizing quantitation of the chronic inflammatory cells in the lamina propria. Alcoholic patients were found to have a higher incidence of chronic gastritis of the antrum than nonalcoholics (p less than 0.001). Fundic involvement was also more common, probably accounting for the decreased gastric acid output described in chronic alcoholic patients. Finally, gastritis was more severe in the alcoholics; below 45 years of age chronic atrophic gastritis was seen only in alcoholics. We conclude that chronic gastritis develops more frequently in alcoholic patients and evolves into chronic atrophic gastritis at an earlier age than in nonalcoholic subjects.

Segmental tuberculosis of the colon mimicking carcinoma.

Tuberculosis of the distal colon occurring in the absence of ileocecal or pulmonary involvement is often mistaken for neoplasm or Crohn's disease. In spite of various studies, including colonoscopy and brushings with biopsy, the diagnosis might still be in doubt at the time of operation. The combined approach of surgery and chemotherapy appears to be the treatment of choice, especially in those patients who have bleeding and/or obstruction in whom the diagnosis cannot be made by other modalities.

On the difference between colonic and small intestinal alkaline phosphatase.

Colonic and small intestinal alkaline phosphatase extracts were studied biochemically and electrophoretically to elucidate the source of a reported difference in cellulose acetate electrophoretic mobility. Both preparations were inactivated with 0.5 mmol/L L-phenylalanine but retained full activity in the presence of 1.0 mmol/L tetramisole. Treatment with neuraminidase changed a minor fraction of the small intestinal but the major portion of the colonic alkaline phosphatase to a cathodically migrating form. The most likely explanation for our findings is that the colon and small intestinal alkaline phosphatase are mixtures of the same multiple forms but in different proportions.