Time courses of calcium and calcium-bound buffers following calcium influx in a model cell

Fixed and diffusible calcium (Ca) buffers shape the spatial and temporal distribution of free Ca following Ca entry through voltage-gated ion channels. This modeling study explores intracellular Ca levels achieved near the membrane and in deeper locations following typical Ca currents obtained with patch clamp experiments. Ca ion diffusion sets an upper limit on the maximal average Ca concentration achieved near the membrane. Fixed buffers restrict Ca elevation spatially to the outermost areas of the cell and slow Ca equilibration. Fixed buffer bound with Ca near the membrane can act as Ca source after termination of Ca influx. The relative contribution of fixed versus diffusible buffers to shaping the Ca transient is determined to a large extent by the binding rate of each buffer, with diffusible buffer dominating at equal binding rates. In the presence of fixed buffers, diffusible buffers speed Ca equilibration throughout the cell. The concentration profile of Ca-bound diffusible buffer differs from the concentration profile of free Ca, reflecting theoretical limits on the temporal resolution which can be achieved with commonly used diffusible Ca indicators. A Ca indicator which is fixed to an intracellular component might more accurately report local Ca concentrations.     

Thrombolytic and endovascular treatment of peripartum iliac vein thrombosis: a case report

This case report details the multidisciplinary treatment of peripartum left iliac vein thrombosis using percutaneous catheter-directed urokinase thrombolysis and balloon thromboplasty. Enhanced chances for long-term patency and the normalization of venous function make these minimally invasive procedures accepted options for the treatment of iliofemoral deep venous thrombosis in selected peripartum patients.     

Role of glutathione, glutathione S-transferases and multidrug resistance-related proteins in cisplatin sensitivity of head and neck cancer cell lines

Spontaneous proliferative liver lesions were found in 15 (13 males and 2 females) of 244 (122 of each sex) transgenic (Tg) mice carrying the human prototype c-H-ras gene (rasH2). The liver lesions included 3 foci of cellular alteration, 1 hepatocellular adenoma, 5 hepatocellular carcinomas, and 4 hepatic hemangiosarcomas in the males and 1 focus of cellular alteration and 1 hepatocellular carcinoma in the females. The mutation patterns of the human and endogenous mouse c-H-ras codon 61 in these proliferative liver lesions were analyzed by DNA amplification using polymerase chain reaction, single-strand conformation polymorphism (PCR-SSCP), and oligonucleotide dot blot hybridization. The hepatocellular carcinomas in 4 males and 1 female contained a point mutation in the mouse c-H-ras gene: 3, 1, and 1 carcinomas had a CAA to AAA transversion at the first base of codon 61, a CAA to CTA transversions, and a CAA to CGA transition at the second base of codon 61, respectively. No point mutations in the human c-H-ras transgene were detected in any hepatocellular carcinoma. All 4 hepatic hemangiosarcomas had a CAG to CTG transversion at codon 61 of the human c-H-ras gene, but no point mutations were detected in codon 61 of the mouse c-H-ras gene. No mutations in human or mouse c-H-ras codon 61 were detected in altered cell foci or hepatocellular adenoma. These results indicate that spontaneous liver tumors in rasH2 Tg mice contain different mutation patterns depending on the histologic type or cell origin of the tumors (i.e., hepatocellular carcinomas or hepatic hemangiosacomas). The absence of similar mutations in foci of cellular alteration and the hepatocellular adenoma suggests that the occurrence of codon 61 point mutations is a late event in the progression of hepatocellular neoplasia in rasH2 Tg mice.     

In vitro degradation of dermal sheep collagen cross-linked using a water-soluble carbodiimide

Bacterial collagenase was used to study the susceptibility of dermal sheep collagen (DSC) cross-linked with a mixture of the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide hydrochloride and N-hydroxysuccinimide (E/N-DSC) towards enzymatic degradation. Contrary to non-cross-linked DSC (N-DSC), which had a rate of weight-loss of 18.1% per hour upon degradation, no weight loss was observed for E/N-DSC during a 24 h degradation period. The tensile strength of the E/N-DSC samples decreased during this time period, resulting in partially degraded samples having 80% of the initial tensile strength remaining. The susceptibility of E/N-DSC samples towards enzymatic degradation could be controlled by varying the degree of cross-linking of the samples. Ethylene oxide sterilization of E/N-DSC samples made the material more resistant against degradation compared with non-sterilized E/N-DSC samples. This may be explained by a decrease of the adsorption of bacterial collagenase onto the collagen owing to reaction of ethylene oxide with remaining free amine groups in the collagen matrix.     

Adolescents and children injured or killed in drive-by shootings in Los Angeles

BACKGROUND: Drive-by shootings by violent street gangs contribute to early morbidity and mortality among adolescents and children in Los Angeles. This study attempted to determine the frequency of this problem and the population at greatest risk. We also studied the most frequently injured areas of the body, the seasons in which the most shootings occurred, the most common sites for drive-by shootings, and the types of firearms used. METHODS: We retrospectively reviewed the files of the Gang Information Section of the Los Angeles Police Department to identify all drive-by shootings in Los Angeles in 1991 in which a child or adolescent under the age of 18 was shot at, injured, or killed. RESULTS: A total of 677 adolescents and children were shot at, among whom 429 (63 percent) had gunshot wounds and 36 (5.3 percent) died from their injuries. Three hundred three of those with gunshot wounds (71 percent) were gang members. Arms and legs were the areas of the body most commonly injured. Handguns were the most frequently used type of firearm. All the homicide victims were African American or Hispanic, and 97 percent were boys. African American and Hispanic children and adolescents, especially male gang members, had a significantly higher risk than their Asian and white counterparts of injury and death from drive-by shootings in Los Angeles (P < 0.001). CONCLUSIONS: Drive-by shootings involving adolescents and children are frequent in Los Angeles. Although Los Angeles may be an atypical case, understanding why violent street gangs form, preventing causes of violence, and limiting access to firearms are essential steps in preventing this serious problem.     

Preparation of compound-specific and group-specific antibodies to 7-methylguanine and related 7-alkylguanines and their use in immunoaffinity purification

The preparation and characteristics of compound-specific and group-specific antibodies against 7-alkylguanines (7-alkGua) are described. A compound-specific antibody against 7-methylguanine was prepared using a hapten bound to carrier protein through the N2 position. In a competitive enzyme-linked immunosorbent assay (ELISA) 7-methylguanine (7-MeGua) showed 50% inhibition (I50%) at 10 pmol/well at room temperature, but the inhibition was found to be 40 times better at 4 degrees C (I50% at 250 fmol/well). When the antibody was bound to protein A-Sepharose CL4B 7-MeGua was retained in immunoaffinity columns. A group-specific antibody to 7-alkGua was prepared using 7-(2-carboxyethyl)guanine (7-CEGua) bound to carrier protein via the carboxyl group. In a competitive ELISA, this antibody cross-reacted well with 7-CEGua, 7-ethylguanine (7-EtGua), 7-(2-hydroxyethyl)guanine (7-HOEtGua) and 7-(2',3'-dihydroxy)-propylguanine (7-DHPGua) and some inhibition was seen with 7-MeGua. Immunoaffinity columns prepared from this antibody retained a number of 7-alkGua of diverse structure. 7-EtGua in calf thymus DNA treated with diethylsulphate and ethylnitrosourea was isolated by immunoaffinity purification and quantified by HPLC-fluorescence. These results illustrate the potential of immunoaffinity purification for both individual DNA adducts and groups of adducts.     

Low-power digital radio as a ubiquitous subscriber loop

The recent growth in the use of digital radio is reviewed. The technology used to implement low-power digital radio in the local exchange loop plant is discussed. The integration of digital radio subscriber loops withnetwork intelligence is explored. The relationship between low-power digital radio loops and broadband fiber loops is briefly examined, and standards and frequency allocation activities are summarized