The causes of femoral head roughening in explanted Charnley hip prostheses

The effect of particles of first, acrylic bone cement containing either barium sulphate or zirconium dioxide as X-ray contrast media, and secondly, particles of fresh cortical bone, on a surgical grade stainless steel surface against which polyethylene was rubbing, has been investigated. It was found that under physiological loads, particles of acrylic cement which have been embedded in the polyethylene bearing surface caused severe scratching of the stainless steel. Some scratches were found to have pronounced lips similar to those observed on the femoral heads of explanted Charnley hip prostheses. Cortical bone produced only slight damage to the stainless steel. In the case of the acrylic cements, the abrasive constituent was isolated and found to be clusters of particles of the X-ray contrast medium. Particles of acrylic cement are frequently observed embedded in the wear surfaces of explanated Charnley acetabular cups and these particles have also been found to contain clusters of X-ray contrast medium particles. It is therefore concluded that the damage to implanted stainless steel prostheses is predominantly caused by the X-ray contrast medium in the acrylic cement.

Localized non-Hodgkin's lymphoma of the breast

Chart review identified 18 patients seen at Memorial Hospital from 1970 to 1984 with primary non-Hodgkin's lymphoma localized to the breast. Sixteen involved the breast alone (Stage IE), whereas two also involved ipsilateral axillary lymph nodes (Stage IIE). None had B symptoms. Histologic subtypes included 11 diffuse histiocytic, 4 diffuse poorly differentiated, 2 diffuse mixed and one nodular mixed. Thirteen patients (72%) are alive with 55 months median follow-up (11 months-14 years). Three patients died with recurrent disease at less than 2 years, one recurred at 4 years and died 6 years after diagnosis, and one died at 30 months without clinical evidence of disease. Seven (39%) have remained continuously disease-free (11 months-11 years; median, 54 months). Of the clinical Stage I patients, 1 of 3 treated with mastectomy alone recurred in the scar, whereas 1 of 12 treated with irradiation alone recurred locally. Thus, radiation therapy alone achieved good local control, although distant relapses remain a problem in these clinically staged patients. Overall, the outcome of clinically localized non-Hodgkin's lymphoma of the breast is similar to that for localized lymphoma in other sites.

CA-125. Use as a tumor marker with mixed mesodermal tumors of the female genital tract

CA-125 levels were determined in seven patients with a mixed mesodermal tumor of the ovary or endometrium. An elevated level was detected in five of six patients with metastatic or recurrent disease. Chemotherapy with cisplatin and Adriamycin (doxorubicin) resulted in a response in four patients, and the CA-125 level correlated well with the clinical status of the disease. Cisplatin/Adriamycin is an active combination in mixed mesodermal tumors and CA-125 appears to be a useful marker for following therapy.

Improved delineation of human dopamine receptors using [18F]-N-methylspiroperidol and PET

The brain uptake of [18F]-N-methylspiroperidol, a butyrophenone neuroleptic with high selectivity for the dopamine receptor, has been measured in three normal human volunteers using positron emission tomography for times up to 12 hr postinjection. These studies demonstrated two unique findings concerning the in vivo distribution of this neuroleptic: (a) it is tightly bound to dopamine D-2 receptors in the caudate-putamen brain regions, and (b) these regions are the only large brain structures which exhibit appreciable long-term retention. In addition, radioactivity clears rapidly from plasma, and the percentage of unchanged [18F]-N-methylspiroperidol in plasma declines rapidly. These results suggest that this compound binds irreversibly to dopamine D-2 receptors, and that there are few if any dopamine D-2 receptors in the human frontal cortex. These studies emphasize not only the importance of characterizing neurotransmitter receptors in living human brain using a ligand labeled with a positron emitting nuclide of sufficiently long half-life to allow monitoring of brain radioactivity distribution for several hours after the injection of radioligand, but also of accurately determining the amount of unchanged tracer in plasma for tracer kinetic modeling.

Salvage therapy with whole-abdominal irradiation in patients with advanced carcinoma of the ovary previously treated by combination chemotherapy

Whole-abdominal irradiation was delivered to 22 patients with epithelial carcinoma of the ovary who had persistent disease after chemotherapy. Seventeen patients were treated with an open whole-abdominal field and 5 with the moving-field technique. Eleven of the 22 also received a pelvic boost. Two of nine patients with microscopic disease at second look are alive and disease-free at 34 and 52 months, respectively. There were no salvages among the patient with macroscopic disease. Major complications included bowel obstruction in three patients and radiation enteritis in one patient. Whole-abdominal irradiation is not an effective salvage regimen after multiagent chemotherapy.

Reversal of transformed phenotype by monoclonal antibodies against Ha-ras p21 proteins

The transforming activities of p21 ras proteins have been determined by micro-injection of these proteins into NIH3T3 cells. In order to facilitate functional studies on the effect of ras proteins on malignant transformation and normal cellular growth, analysis has been made with three monoclonal antibodies (YA6-172, Y13-238 and Y13-259) as originally reported by Furth et al. (J virol 43 (1982) 294). Purified immunoglobulin of Y13-259 has the highest titer of binding to bacterially synthesized p21 ras proteins. Experimental analyses indicate that only Y13-259 antibody will neutralize the transforming activity of the co-injected bacterially synthesized ras protein and the neutralization effect was blocked by co-injection of excess ras protein. In addition, micro-injection of Y13-259 immunoglobulin into transformed NIH3T3 cells (obtained by DNA transfection of NIH3T3 cells with molecularly cloned ras gene) reversed their transformed phenotypes. These results indicate that both bacterially synthesized p21 ras proteins and the natural ras proteins produced in NIH3T3 cells were neutralized by Y13-259 antibody.

Application of autoregressive moving average parametric modeling in magnetic resonance image reconstruction

The modeling of data is an alternative to conventional use of the fast Fourier transform (FFT) algorithm in the reconstruction of magnetic resonance (MR) images. The application of the FFT leads to artifacts and resolution loss in the image associated with the effective window on the experimentally-truncated phase encoded MR data. The transient error modeling method treats the MR data as a subset of the transient response of an infinite impulse filter (H(z) = B(z)IA(z)). Thus, the data are approximated by a deterministic autoregressive moving average (ARMA) model. The algorithm for calculating the filter coefficients is described. It is demonstrated that using the filter coefficients to reconstruct the image removes the truncation artifacts and improves the resolution. However, determining the autoregressive (AR) portion of the ARMA filter by algorithms that minimize the forward and backward prediction errors (e.g., Burg) leads to significant image degradation. The moving average (MA) portion is determined by a computationally efficient method of solving a finite difference equation with initial values. Special features of the MR data are incorporated into the transient error model. The sensitivity to noise and the choice of the best model order are discussed. MR images formed using versions of the transient error reconstruction (TERE) method and the conventional FFT algorithm are compared using data from a phantom and a human subject. Finally, the computational requirements of the algorithm are addressed.

Application of autoregressive modelling in magnetic resonance imaging to remove noise and truncation artifacts

Magnetic resonance imaging data is conventionally reconstructed using two dimensional discrete Fourier transforms. However, there is growing interest in other types of spectral estimation which minimize noise and artifacts due to truncated data. This note presents preliminary results--showing the improvement obtainable using a modified autoregressive model, the Transient Error method.

Requirement for c-ras proteins during viral oncogene transformation

Many retroviral oncogenes have been classified into one of several categories based on structure, enzymology and cellular localization. These genes originated from host cells and are probably derived from genes normally involved in the control of cell proliferation. The cellular counterparts of three oncogenes have been identified as a growth factor or growth factor receptor; related oncogenes include receptor-like membrane proteins which often express tyrosine kinase activity. These growth factor-related oncogenes are structurally and biochemically distinct from the membrane-associated ras gene family, which bind and hydrolyse GTP. Oncogenes localized primarily in the cytoplasm which probably have serine kinase activity, have also been identified. Although the structure and biochemistry of many oncogenes have been extensively studied, relatively little is known about the functional relationships of oncogene proteins within the cell. An opportunity to study such interaction is provided by the identification of a monoclonal antibody that neutralizes cellular ras proteins when microinjected into cells. It has been shown previously that the injected antibody inhibits the initiation of S-phase in NIH 3T3 cells. In the present study we injected this monoclonal antibody into NIH 3T3 cells transformed by a variety of oncogenes. The results show that transformation by three growth factor receptor-like oncogenes depends on c-ras proteins, while transformation by two cytoplasmic oncogenes appears to be independent of c-ras protein.

Methanosarcina mutant unable to produce methane or assimilate carbon from acetate

Mutants of Methanosarcina barkeri 227 resistant to monofluoroacetate were isolated from monofluoroacetate-treated cultures. Mutant strain FAr9 was 100 times more resistant to monofluoroacetate than the wild-type strain and was deficient in carbon uptake and CH4 and CO2 production from methyl-labeled acetate. Methanol was assimilated at increased levels. Strain FAr9 was unable to shift from using methanol to using acetate for growth and exhibited increased sensitivity to growth inhibition by NaCN in methanol-containing complex medium. Unlike parent strain 227, acetate addition to methanol-containing media did not prevent NaCN inhibition. The specific activities of enzymes of exogenous acetate assimilation, CO dehydrogenase, and enzymes of the tricarboxylic acid cycle were similar for mutant and parent strain cell extracts. Mutation to monofluoroacetate resistance did not confer simultaneous resistance to 2-bromoethanesulfonate or pyruvate or alter propionate uptake. We conclude that strain FAr9 is either an acetate permeability mutant or is defective in an activation step required for the catabolism and anabolism of acetate.

Non-Hodgkin's lymphoma and membranous nephropathy in mixed connective tissue disease

A 60-year-old woman with a diagnosis of poorly differentiated lymphocytic lymphoma presented with nephrotic syndrome. Her clinical picture and serological studies were consistent with the diagnosis of mixed connective tissue disease (MCTD). Renal biopsy demonstrated the changes of membranous nephropathy by light, immunofluorescence and electron microscopy. Treatment with corticosteroids and cyclophosphamide had no effect on the proteinuria, and she demonstrated progression of renal failure. This patient demonstrates that the lymphadenopathy associated with MCTD may be of a separate malignant origin. The treatment of MCTD may not alter the course of renal disease, and renal failure may ensue in patients with MCTD.

Relation of effectiveness of intracoronary thrombolysis in acute myocardial infarction to systemic thrombolytic state

Twenty-nine patients received intracoronary thrombolytic therapy for acute myocardial infarction 3.5 +/- 1.4 hours (mean +/- standard deviation) after the onset of pain. Ten patients received urokinase (UK) and 19 patients received streptokinase (SK). Laboratory variables of the coagulation system were measured before and immediately after therapy. When comparing patients in whom coronary artery recanalization occurred vs those in whom the artery remained occluded, those in whom recanalization was achieved had greater alterations in fibrinogen, prothrombin time, activated partial thromboplastin time, fibrin/fibrinogen degradation products and plasminogen by thrombolytic therapy than did those in whom recanalization was not achieved (p less than 0.05 for all variables). Euglobulin lysis time showed a similar but nonsignificant trend (p = 0.114). Patients who received SK showed markedly greater alterations in coagulation parameters than did patients treated with UK (p less than 0.05 for 5 of 6 variables measured) and had a much higher incidence of successful thrombolysis (74% for SK, 20% for UK). These data indicate that the development of a systemic fibrinolytic state contributes to success when using intracoronary thrombolytic agents in acute myocardial infarction. Rather than being considered an adverse effect of therapy, a systemic lytic state may serve as a reasonable clinical goal in attempting to produce thrombolysis.

Inhibition of methanogenesis and carbon metabolism in Methanosarcina sp. by cyanide

NaCN was tested for its inhibitory effects on growth of and metabolism by Methanosarcina barkeri 227. NaCN (10 microM) inhibited catabolism of acetate methyl groups to CH4 and CO2 but did not inhibit methanogenesis from methanol, CO2, methylamine, or trimethylamine. NaCN also inhibited the assimilation of methanol or CO2 (as the sole carbon source) into cell carbon and stimulated the assimilation of acetate. These results suggest that inhibition by NaCN was a result of its action as an inhibitor of in vivo CO dehydrogenase. The results also implicate CO dehydrogenase in the oxidation of acetate but not methanol methyl groups to CO2.

Requirement for ras proto-oncogene function during serum-stimulated growth of NIH 3T3 cells

Human tumours often contain DNA sequences not found in normal tissues which are able to transform cultured NIH 3T3 cells. In some tumours the gene responsible for this transformation belongs to the cellular ras gene family. A specific type of mutation is responsible for converting the cellular proto-oncogene into a ras oncogene capable of inducing transformation. In a study of the function of a cellular ras gene, its protein product (produced in a bacterial cell) was microinjected into NIH 3T3 cells; the recipient cells became morphologically transformed and were induced to initiate DNA synthesis in the absence of added serum, but only when cellular ras protein was injected at much higher concentrations than required with protein of the transforming ras gene. To further analyse the function of the cellular ras gene, we have now injected monoclonal antibodies against ras proteins into NIH 3T3 cells. We report here that NIH 3T3 cells induced to divide by adding serum to the culture medium are unable to enter the S phase of the cell cycle after microinjection of anti-ras antibody, showing that the protein product of the ras proto-oncogene is required for initiation of the S-phase in NIH 3T3 cells.

RE Pulse Shapes for Selective Excitation in NMR Imaging

It is shown that the requirements of an RF pulse needed to produce a slice for use in NMR imaging approximate the requirements of the windows used for calculating the discrete Fourier transform (DFT). This approach gives an interesting insight into the physical background of pulse shape tailoring. One of the more successful DFT windows is the 3 term Blackman-Harris window, which is tailored to produce minimum sidelobes. The results of applying radio frequency (RF) pulses modulated to give this window shape is given. The pulse shape produces a uniform magnetization over a range of frequencies with a quasi-linear phase shift making it suitable for producing a slice for NMR imaging when an echo is produced via an inverse magnetic field gradient.

Promotion of bladder tumours by endoscopic procedures in an animal model

An experimental study was performed to assess the possible tumour-promoting action of urothelial trauma caused by repeated intravesical diathermy, catheterisation, and the instillation of water, glycine and saline in the rat bladder which had previously been exposed to an initiating dose of the carcinogen N-methyl-N-nitrosourea. An increase in tumours and inflammatory changes was observed, especially in the group treated with water, and the significance of the findings is discussed.

Nucleosome arrangement in alpha-satellite chromatin of African green monkey cells

By analyzing the accessibility of restriction endonuclease sites in African green monkey alpha-satellite chromatin, we demonstrate the absence of a unique phase relationship between nucleosomes and alpha-satellite DNA. The data indicate a minimum of three different positions for nucleosome cores relative to the alpha-satellite sequence and suggest a random distribution in at least some regions. In addition, while we confirm published reports that staphylococcal nuclease cuts the alpha-satellite sequence in chromatin at a highly preferred site, two-dimensional gel electrophoresis of nuclear digests demonstrates that this site is preferentially cut by staphylococcal nuclease even when it is within the nucleosome core. These data indicate that staphylococcal nuclease is not useful for determining nucleosome positions on alpha-satellite DNA, and perhaps on other specific DNA sequences as well.

Caries inhibition of a dentifrice containing 0.78% sodium monofluorophosphate in a silica base

The purpose of this double blind clinical trial was to determine the anticaries activity of a dentifrice containing 0.78% sodium monofluorophosphate in a silica gel abrasive base compared with a placebo under conditions of supervised brushing. 1154 schoolchildren, ages 9-12, were recruited in a non-fluoridated semi-rural area of northeastern Connecticut. Subjects were stratified according to school, grade and sex, and then randomly divided into two groups. Each school day, children brushed their teeth for 1 min under supervision by project personnel. Weekend and vacation usage was ad libitum. Caries examinations and radiographic readings were performed by the same examiner (J.R.). After 12 months, the 996 subjects examined showed that the group using the test dentifrice had significantly (less than 0.05) lower DMFT (25.0%) and DMFS (19.1%) increments than the group using the placebo. After 24 months the 876 subjects examined showed that the test group continued to have significantly lower DMFT (24.5%) and DMFS (24.7%) increments than the placebo group. Surface protection after 24 months ranged from 22.1% for occlusal to 37.1% for interproximal surfaces.

A linguist's view of the Bellman-Goldberg thesis

From a linguistic perspective, the Bellman-Goldberg thesis of a necessary relationship between the abilities of organisms to move and communicate is very interesting. Since several concepts and terms are represented in both the thesis and contemporary linguistic literature, these items are discussed in further detail. Questions of the implicit assumptions of the homology of the motor and linguistic systems are also raised here. Finally, there are requests for further clarification on issues of evolution in this test of the strength of the thesis.

Intrinsic characteristics of activity: a comment on Kent's psychobiology

Kent has made seven statements that should inspire responses from linguists, kinesiologists, and developmentalists, among others. His goal of reforming our current theoretical perspective on the development of speech will be accomplished, in part, by their corrections, elaborations, and further speculations. Not all of his statements have the same status or consequence for an evolving theory of development. Those on the anatomic and neurological differences between infants and adults are much less controversial than those on the initial separateness of the perception and production systems or those on the relation of rhythmic behavior to phonology. Across all the statements, two major topics merit discussion: 1) the relevant descriptive terms of the vocal behavior of infants and 2) the relation of vocal activity to other behavior.

Implementation and evaluation of a model geriatrics curriculum

An evaluation of a case-based, problem-oriented, modular curriculum in geriatrics for medical students was designed by the authors to investigate (a) whether students would demonstrate cognitive knowledge gain in geriatrics, (b) whether students' attitudes toward the elderly would change favorably, (c) whether suggested learning activities in geriatrics would positively influence students' ratings of these activities in geriatrics, and (d) which institutional characteristics facilitate implementation of the new curriculum. The results indicated that using the modules did produce statistically significant gains in students' cognitive knowledge of geriatrics. Using the modules did not, however, influence the students' attitudes toward the elderly. Clinical or related learning activities involving elderly persons were rated positively by students; however, only two of the participating medical schools in the evaluation provided such experiences. Data from questionnaires and site visits identified several factors which may be helpful in the implementation of geriatrics or other new curricular material into existing curricular structures.

Quantitative electrophoretic transfer of DNA from polyacrylamide or agarose gels to nitrocellulose

A method for efficient electrophoretic transfer of DNA fragments from polyacrylamide gels to nitrocellulose sheets was developed. Hybridization to these fragments can be performed by standard techniques. The method is also applicable to agarose gels, allowing this transfer method to be used for DNA ranging from 40 to at least 23,000 bp.

Reversal of 2-bromoethanesulfonate inhibition of methanogenesis in Methanosarcina sp

2-Bromoethanesulfonate (BES) inhibition of methanogenesis from methanol by resting-cell suspensions or cell extracts of Methanosarcina was reversed by coenzyme M. BES inhibition of methylcoenzyme M methylreductase activity in cell-free extracts was reversed by methylcoenzyme M but not by coenzyme M. Methanol/coenzyme M methyltransferase activity was not inhibited by 10 microM BES. Inhibition of methylreductase by BES and 3-bromopropionate was competitive with methylcoenzyme M, but inhibition by 2-bromoethanol exhibited mixed kinetics. The Ki values for the inhibitors in cell-free extracts were similar to the concentrations which inhibited intact cells. BES-resistant mutants of strain 227 were apparently permeability mutants because in vitro assays showed that mutant and parent strain methylreductases were equally sensitive to BES.

Estimates of the gain in power utilizing transformations of DMFS scores

More than 100,000 clinical caries trials were simulated utilizing the negative binomial distribution on a UNIVAC 1100 computer. In each trial, the raw data and logarithmic transformed data were analyzed using a standard t test analysis. The results were summarized as estimates of the power functions for each case. In almost all cases, the transformed data gave greater power than did the untransformed data. In several common situations, the differences were dramatic.

Vaginal aplasia: therapeutic options

Müllerian dysgenesis, a common developmental anomaly presenting as primary amenorrhea, is characterized by absence of the vagina and absence or rudimentary development of the uterus. Anatomic anomalies of the axial skeleton, inguinal canal, and kidney often accompany this psychologically devastating condition. Twenty-two cases are reviewed in regard to associated clinical features, principles of treatment, and adequacy of outcome. A good functional result can be achieved either by the use of a progressive nonsurgical self-dilatation technique, or by surgical cavitation with skin grafting, although histologic and steroid receptor properties of the latter are less physiologic than those of the former.

Nephrotoxicity of phenazopyridine

A young man developed reversible acute renal failure after a large overdose of phenazopyridine. The renal failure was treated by peritoneal dialysis. Analysis of blood and urine samples failed to demonstrate the parent drug but a metabolite with similar ultraviolet absorption was detected. No parent drug or metabolites were detected in the peritoneal dialysate.

The effects of mezlocillin, ticarcillin and placebo on blood coagulation and bleeding time in normal volunteers

Bleeding time, coagulation tests and platelet aggregation response to adenosine diphosphate (ADP), epinephrine, arachidonic acid, ristocetin and collagen were determined in 18 normal male volunteers in a randomized, double-blind, placebo-controlled parallel study. Six subjects each received either placebo or 4.0 g of either mezlocillin or ticarcillin every 6 h for 7 days. In the placebo-treated or mezlocillin-treated groups no changes in plasma coagulation tests or bleeding time were observed. Randomly scattered decreases in platelet aggregation responses to ADP, epinephrine or arachidonic acid were noted in some subjects in both the placebo and mezlocillin groups. In contrast to these observations, in the ticarcillin treated group the bleeding time was abnormally prolonged to more than 18 min in three of six volunteers. In two of these subjects, bleeding time was prolonged after only seven ticarcillin doses (28.0 g) and in the third subject after a total of 21 doses (84.0 g). A significant decrease in platelet aggregation (P less than 0.005) induced by ADP was found in these volunteers. Although platelet aggregation response to arachidonic acid and epinephrine also appeared to be reduced in this group, correlation between increased bleeding time and abnormal platelet function was not possible because of the small number of subjects. No changes in other coagulation function were observed. The results suggest that the risk of bleeding disorder is very high with therapeutic doses of ticarcillin but not with comparable doses of mezlocillin.

Normal and low molecular weight heparins: interaction with human platelets

Porcine mucosal heparin was chemically depolymerized. The depolymerization was stopped at different steps to obtain two low molecular weight (LMW) heparins with a molecular weight of 10 000 and 6000, respectively. The LMW heparins were tested in vitro for anti-clotting activities and for platelet serotonin release in different systems in comparison with normal heparins, dermatan and heparan sulphate. After addition of various amounts of heparin preparations to washed platelets, no significant release was observed for all tested heparins. On the contrary, different heparins showed an inhibition of serotonin-release induced by collagen in platelet rich plasma, whereas the ADP-induced release was increased. The effect on the platelet release appears related to the molecular weight. In fact, it is significant only for normal heparins whereas it is not for LMW heparins. A good relation was observed, also, between anti-activated factor X activity/antiglobal clotting activity (Xa/APTT) ratio of different heparins and the effect on platelet release.

Ventricular enlargement in schizophrenia: relationship to positive and negative symptoms

The authors explored the clinical correlates of ventricular enlargement in schizophrenia by comparing 16 patients with "large" ventricles (ventricles more than I SD above the control mean) with 16 patients with the smallest ventricles from a sample of 52 schizophrenic patients. Patients with ventricular enlargement showed some impairment in the sensorium and had a preponderance of "negative" symptoms (e.g., alogia, affective flattening, avolition, anhedonia), while those with small ventricles were characterized by "positive" symptoms (e.g., delusions, hallucinations, positive formal thought disorder, bizarre behavior). These findings suggest that combining a measure of brain structure with the clinical picture may provide a useful new approach to the classification of schizophrenia.

Ventricular enlargement in schizophrenia: definition and prevalence

Ventricular enlargement in schizophrenia as measured by ventricular-brain ratio (VBR) has been described by three different research groups. Because of the possibility that the samples might not be representative of the broad population of schizophrenic patients, questions have been raised about generalizability. The authors report on ventricular enlargement in a rigorously defined but representative sample of schizophrenic patients intermittently hospitalized but living in the community. They provide additional evidence that ventricular enlargement does occur in schizophrenic patients, although not at rates as high as those previously reported. Issues related to the definition of ventricular enlargement, as well as the effects of sampling and choice of a control group, are discussed.

Intraocular carbon dioxide laser photocautery

The indications and contraindications for the use of carbon dioxide laser photocautery at the time of vitrectomy have been reviewed. Indications include posterior retinal tears either in flat or elevated sensory retina; elevated fibrovascular fronds on the optic nerve or elsewhere; flat neovascularization elsewhere, bleeding rubeotic iris vessels. It is also used as a means of panretinal endophotocoagulation. Contraindications include flat disc neovascularization and areas within one disc diameter of the macula and nerve. The advantages and disadvantages of the 10.6 micrometer infrared wavelength of carbon dioxide laser photocautery are discussed.

Attitudes and background factors related to alcohol use among college students

Questionnaire responses showed college students (66 females, 24 males) believed their decisions about drinking were made independently of peer or environmental pressure but light and heavy drinkers made different judgments about their peers' drinking behavior. Home background factors did not predict extent of drinking. Most students started drinking during high school and reported no change in drinking rate since attending college.

Causes of apparent low levels of misonidazole in human tumours

Although the concentration of misonidazole measured in human tumours may appear to be only 50--70% of the corresponding blood level, the concentration within the intra- and extracellular fluid of the tumour may be nearer 100% of the blood level. Causes for these apparent low levels of drug which have been investigated are: 1. Presence of fat in the tissue. 2. Presence of non-cellular material in the tissue. 3. Degradation of the drug by anaerobic metabolism after biopsy. An in vitro experiment to test the partitior fractionation study of the distribution of misonidazole showed that it is distributed mainly in the fluid compartment of the cell and that overall drug levels in tissue are related to the fluid content of the tissue. Serial measurements of misonidazole on tissue after removal from the body have shown that breakdown of the drug occurs when the tissue becomes anoxic. These results suggest that the concentration of misonidazole present within tumour cells is higher than the overall level measured for the tissue and that the enhancement ratio to be expected may therefore be higher also.

New trends in carbon dioxide laser microsurgery

The carbon dioxide laser has been used for cutting and cauterizing tissue in a variety of surgical procedures by means of a dry-field air/tissue interface approach. Recently, a new wet-field CO2 laser technique has been developed and is being used successfully in humans to seal intraocular fibrovascular fronds and retinal tears at the time of vitrectomy, to close rubeotic vessels in the iris, and to excise fibrovascular fronds and epiretinal membranes in cases of severe diabetic retinopathy. Specialized wet-field CO2 laser photosurgical probes for use in gynecologic microsurgery have been developed and are being studied experimentally. Other potential applications include otolaryngologic microsurgery, neurosurgery, and gastrointestinal and urologic wet-field surgery.

Intraocular carbon dioxide laser photosurgery

Intraocular carbon dioxide laser has been used for photocautery and photo-incision as an adjunct to vitrectomy. This utilizes a new fluid-tissue interface application for the 10.6 micrometer wavelength infrared radiation. The use of an intraocular probe with an infrared transmitting window through a pars plana incision allows the placement of infrared energy in a fluid medium. The results of animal experimentation and of preliminary clinical trials in human patients are reported. The carbon dioxide laser appears to be a safe and reliable means of intraocular photocautery and photoincision.

Intraocular carbon dioxide laser photocautery. II. Preliminary report of clinical trials

Carbon dioxide laser photocautery was used successfully intraocularly in human patients to seal fibrovascular fronds and retinal tears at the time of vitrectomy. Closure of rubeotic vessels in the iris was demonstrated histologically. The 10.6-microgram infrared radiation was delivered to the intraocular treatment site by means of 1.5-mm-diameter photocautery probe containing a 1.0-mm-diameter lumen closed at the end with an infrared transmitting window. Treatment was localized to the tissue adjacent to the window. Typical energy dosage was 0.4 W for 2 to 4 s duration. These early clinical trials were carried out under the guidelines established by the Food and Drug Administration; informed consent clearly outlined the experimental nature of these studies.

Intraocular carbon dioxide laser photocautery. I. Animal experimentation

Intraocular carbon dioxide laser photocautery is used to produce localized closure of vascular channels and chorioretinal adhesion in the albino rabbit. The retinal lesion is sharply demarcated because of the high tissue absorption of CO2 laser radiation. Varying degrees of chorioretinal adhesion can be achieved. The CO2 laser photocautery technique may provide a suitable method of closing vessels and sealing retinal tears at the time of vitrectomy. Accurate placement of the cautery tip on the target area can be accomplished under stereoscopic magnified viewing with the operating microscope and contact lens. Electrical shock hazard is completely eliminated with the CO2 laser energy modality.

Pars plana transvitreal carbon dioxide laser photocautery: a new surgical technique

Intraocular carbon dioxide laser photocautery has been used experimentally as well as clinically to surround and seal retinal tears and to treat fibrovascular fronds and blood vessels at the time of vitrectomy. All biologic tissue will absorb the 10.6-microm infrared wavelength; thus the tissue does not have to be pigmented in order to absorb infrared energy. This technique involves no electrical hazard to the patient or surgeon. We have followed patients treated with the carbon dioxide laser, and they have retained improved vision for over 18 months. Intraocular carbon dioxide laser photocautery appears to be a safe, reliable, and effective means of performing intraocular photocautery at the time of vitrectomy.

Distribution of misonidazole in human tumours and normal tissues

Levels of misonidazole in human tumours, normal tissues and blood have been measured in patients given a 1g oral dose of drug before surgery or biopsy. The results show that 50--70% of the blood level was found in a wide range of tumours and that similar levels were found in adjacent normal tissues. Good penetration of drug was achieved within tumours, and up to 90--100% of the blood level was found in the necrotic cyst fluid at the centre of some tumours. CSF studies showed free diffusion into the CNS, which was confirmed by finding 50--70% of the blood level within brain tumours. A delay of passage of drugs into the CSF was noted, which was not found for drug diffusion into bile and saliva.

Distribution and tumour cytotoxicity of the radiosensitizer misonidazole (Ro-07-0582) in C57 mice

The distribution and clearance of misonidazole (MIS = Ro-07-0582) were studied in C57 mouse tissues and in transplants of Lewis lung tumour. The half life of the drug in blood after a dose of 1 mg/g i.p. was 3 h. Some tissues, such as liver, were found to have consistently low MIS levels, and this was found to be due to degradation of the drug after removal of the tissues from the host. The in vivo cytotoxicity of MIS to Lewis lung tumour cells was studied using an in-vitro colony assay. After half of the tumours had been irradiated with 10 Gy to kill most of the oxic cells, the mice received i.p. injections of MIS. To simulate the longer drug exposure of human tumour cells (due to the longer half life in man) a repeated injection regime was used in some mice. There was no significant cell kill after a single dose, but with a prolonged exposure to the drug in the multiply injected animals, cell survival was reduced to 50% of control in both the irradiated and unirradiated tumours. Since the hypoxic fraction of the unirradiated tumour is probably not more than 30%, it would appear that MIS is not selectively cytotoxic to hypoxic cells. However, MIS had a much greater cytotoxic effect upon hypoxic Lewis lung tumour cells in vitro, with very little or no effect on cells grown in air. This would support the theory that the presence of hypoxic cells is essential for the expression of MIS cytotoxicity.

Growth and methanogenesis by Methanosarcina strain 227 on acetate and methanol

Methanosarcina strain 227 exhibited exponential growth on sodium acetate in the absence of added H(2). Under these conditions, rates of methanogenesis were limited by concentrations of acetate below 0.05 M. One mole of methane was formed per mole of acetate consumed. Additional evidence from radioactive labeling studies indicated that sufficient energy for growth was obtained by the decarboxylation of acetate. Diauxic growth and sequential methanogenesis from methanol followed by acetate occurred in the presence of mixtures of methanol and acetate. Detailed studies showed that methanol-grown cells did not metabolize acetate in the presence of methanol, although acetate-grown cells did metabolize methanol and acetate simultaneously before shifting to methanol. Acetate catabolism appeared to be regulated in response to the presence of better metabolizable substrates such as methanol or H(2)-CO(2) by a mechanism resembling catabolite repression. Inhibition of methanogenesis from acetate by 2-bromoethanesulfonate, an analog of coenzyme M, was reversed by addition of coenzyme M. Labeling studies also showed that methanol may lie on the acetate pathway. These results suggested that methanogenesis from acetate, methanol, and H(2)-CO(2) may have some steps in common, as originally proposed by Barker. Studies with various inhibitors, together with molar growth yield data, suggest a role for electron transport mechanisms in energy metabolism during methanogenesis from methanol, acetate, and H(2)-CO(2).

Transvitreal carbon dioxide laser photocautery and vitrectomy

A new form of carbon dioxide laser has been developed that allows placement of infrared energy within a fluid medium. Transvitreal photocautery, vitrectomy, and laser scalpel incisions have been accomplished utilizing this delivery modality of infrared energy. Clinical trials are presently underway.