Standards for the Characterization of Endurance in Resistive Switching Devices

Resistive switching (RS) devices are emerging electronic components that could have applications in multiple types of integrated circuits, including electronic memories, true random number generators, radiofrequency switches, neuromorphic vision sensors, and artificial neural networks. The main factor hindering the massive employment of RS devices in commercial circuits is related to variability and reliability issues, which are usually evaluated through switching endurance tests. However, we note that most studies that claimed high endurances >10⁶ cycles were based on resistance versus cycle plots that contain very few data points (in many cases even <20), and which are collected in only one device. We recommend not to use such a characterization method because it is highly inaccurate and unreliable (i.e., it cannot reliably demonstrate that the device effectively switches in every cycle and it ignores cycle-to-cycle and device-to-device variability). This has created a blurry vision of the real performance of RS devices and in many cases has exaggerated their potential. This article proposes and describes a method for the correct characterization of switching endurance in RS devices; this method aims to construct endurance plots showing one data point per cycle and resistive state and combine data from multiple devices. Adopting this recommended method should result in more reliable literature in the field of RS technologies, which should accelerate their integration in commercial products.

Canine Mastocytoma

Utilizing a modified capillary tube technique, analysis revealed a significantly higher mean blood coagulation time in a group of 14 dogs with mastocytoma when compared to the mean coagulation time of 70 non-mastocytoma dogs. In dogs with mastocytoma, approximately one third had intermediate size tumors and a prolonged mean coagulation time and two thirds had a mean coagulation time that did not differ significantly from the mean of the non-mastocytoma dogs. Evidence for heparin release and possible heparin inactivating mechanisms is reviewed.

X-ray spectromicroscopy investigation of soft and hard breakdown in RRAM devices

Resistive random access memory (RRAM) is considered an attractive candidate for next generation memory devices due to its competitive scalability, low-power operation and high switching speed. The technology however, still faces several challenges that overall prohibit its industrial translation, such as low yields, large switching variability and ultimately hard breakdown due to long-term operation or high-voltage biasing. The latter issue is of particular interest, because it ultimately leads to device failure. In this work, we have investigated the physicochemical changes that occur within RRAM devices as a consequence of soft and hard breakdown by combining full-field transmission x-ray microscopy with soft x-ray spectroscopic analysis performed on lamella samples. The high lateral resolution of this technique (down to 25 nm) allows the investigation of localized nanometric areas underneath permanent damage of the metal top electrode. Results show that devices after hard breakdown present discontinuity in the active layer, Pt inclusions and the formation of crystalline phases such as rutile, which indicates that the temperature increased locally up to 1000 K.

THE CHARACTERIZATION OF STAPHYLOCOCCAL TOXINS : II. THE ISOLATION AND CHARACTERIZATION OF A HOMOGENEOUS STAPHYLOCOCCAL PROTEIN POSSESSING ALPHA HEMOLYTIC, DERMONECROTIC, LETHAL, AND LEUCOCIDAL ACTIVITIES

The continuous flow paper electrophoretic methods used to isolate alpha hemolysin are presented. The purity of the alpha hemolysin preparation is demonstrated by double agar diffusion, immunoelectrophoretic, and ultracentrifugation techniques. Indirect evidence of purity is provided by the fact that rabbit immunized with purified alpha hemolysin produced detectable antibody only to alpha hemolysin. Direct support is given to the "unitarian theory" by the demonstration that purified alpha hemolysin also possessed dermonecrotic, lethal, and leucocidal activities. Further studies dependent on the availability of purified alpha hemolysin are outlined.

Towards population inversion of electrically pumped Er ions sensitized by Si nanoclusters

This study reports the estimation of the inverted Er fraction in a system of Er doped silicon oxide sensitized by Si nanoclusters, made by magnetron sputtering. Electroluminescence was obtained from the sensitized erbium, with a power efficiency of 10(-2)%. By estimating the density of Er ions that are in the first excited state, we find that up to 20% of the total Er concentration is inverted in the best device, which is one order of magnitude higher than that achieved by optical pumping of similar materials.

Increasing the efficiency of erbium-based sources using silicon quantum dots

Silicon nanoclusters exhibit novel and interesting optical and electrical properties that are not observed in bulk silicon. Moreover, it has been discovered that there exists a strong coupling between nanoclusters and rare-earth ions that results in efficient energy exchange between the two species. This paper presents a review of recent work at University College London in this area, in which we have studied the optical properties of silicon nanoclusters in silica with rare-earth co-dopants and have developed a model for the excitation of erbium ions in erbium-doped silicon nanocrystals via coupling from optically generated excitons confined within the silicon nanoclusters. The model provides a phenomenological description of the exchange mechanism and allows us to evaluate an effective absorption cross-section for erbium that is up to four orders of magnitude higher than the corresponding value in stoichiometric silica. This paper also discusses the origin of the 1.6 eV emission band associated with the silicon nanoclusters and determines absorption cross-sections and excitonic lifetimes for nanoclusters in silica.

Comparison of antipseudomonad activity of chlorine dioxide/chlorous acid-containing gel with commercially available antiseptics

A chlorine dioxide-containing gel was compared with 3 commercially available antimicrobials and 1 antibiotic intended for topical use. This gel was tested at 0.5 X and 4 X and was found to be more effective as a 4 X gel in treating Pseudomonas aeruginosa-infected excised wounds on mice. To further compare this gel with other antiseptics, a murine bioassay was developed. This wound model consisted of an excised cutaneous wound on the dorsum of mice which were irradiated (800 rad) and inoculated with P aeruginosa at 10-fold dilutions, from 10(-2) to 10(-10). The wounds were observed for latency of infection or mice survival time as a function of concentration of viable organisms remaining after treatment. The advantage of this model was demonstrated where a standard curve based on latency did not consume as many test subjects and yet provided an estimate of viable organisms in each wound. In this model, the chlorine dioxide-containing gel was more active than were preparations of providone-iodine, chlorhexidene, or silver sulfadiazine and was similar to polymyxin-bacitracin-neomycin ointment as a topical antiseptic. The effectiveness of the tested gel was reduced if delays in treatment were longer than 1 hour.

Controlled wound repair in guinea pigs, using antimicrobials that alter fibroplasia

The repair processes of incised wounds depend, in part, on fibroplasia induced by soluble mediators from monocytic macrophages. Two topical antimicrobials were evaluated, each of which effectively controlled wound sepsis and yet each had widely different effects on fibroplasia and wound strength. Paired-incision dermal wounds on the flanks of guinea pigs were treated with a substance containing reactive chlorine (Alcide) or with a compound that is a mixture of two surfactants. One side of each guinea pig was treated with one of the antimicrobials (treated wounds); the opposite side was treated with isotonic saline solution (control wounds). At 7, 10, and 16 days after surgery, tensiometric measurements of C31G (a surfactant)-treated wounds were 99%, 139%, and 195% of control wound values, respectively. Alcide-treated wounds were 76%, 58%, and 88% of control wounds, respectively. Wounds treated with chlorhexidine had reduced strength at 7 days (73%) and at 10 days (78%), but by 14 days, they were similar to control wounds (94%). The main difference between the wounds was the amount of collagen formation. Alcide-treated wounds incorporated less than 50% of the amount of 14C-proline than did the wounds treated with C31G. However, Alcide-treated wounds epithelialized as rapidly as did control wounds, and had minimal scar formation. Microscopic evaluations indicated greatly reduced inflammatory infiltrates in Alcide-treated wounds, indicating that reduced wound strength may be associated with lack of fibroblast-stimulating activity by monocytes.

Comparison of early splenic changes associated with replication of viruses in murine monocytic macrophages

An effect of replication of certain viruses in murine monocytic macrophages was manifested by depletion of cells through degenerative and necrotizing changes in thymus-dependent areas of lymphoid structures. In mice infected with murine hepatitis virus (MHV-3) or lactate dehydrogenase virus, these changes were transient in mice killed on postinoculation day (PID) 2. To study these morphologic changes due to viral replication, adult Swiss specific-pathogen-free homozygous nude mice (nu/nu) and their heterozygous haired littermates (nu/+) were inoculated with 10(5) LD50 of MHV-3, euthanatized, and necropsied on PID 1, 2, 4, 6, 8, and 10 along with noninoculated controls. The nu/+ and nu/nu mice killed on PID 2 had lymphocytic karyorrhexis and depletion of cells in the thymus-dependent area. In the heterozygote, these characteristic lesions were transient; whereas in the homozygote, lesions persisted and were present in survivors euthanatized and necropsied on PID 16. Although the intensity of lesions due to MHV-3 varied between nu/+ and nu/nu mice, virus titers determined on liver homogenates were similar for the homozygote and heterozygote during acute disease. Nude and nonnude mice given lactate dehydrogenase virus and killed on PID 2 had a transient depletion of lymphocytes; whereas mice given lymphocytic choriomeningitis virus and killed on PID 4 had a similar lesion. Lesions neither occurred when mice were treated with silica before inoculation, indicating that functional monocytic macrophages were required, nor occurred when another virus, herpes simplex virus type 1, was given.

Histamine-induced suppressor macrophage inhibits fibroblast growth and wound healing

To determine whether there is histamine-induced suppressor activity in macrophage-related functions other than in immunity, extracts and media from a macrophage cell line, RAW 264, were tested for suppressor effect on fibroplasia. The procedure consisted of priming confluent RAW 264 cells in culture with media or cellular extracts of washed mastocytes (P-815). The inoculum was removed from the RAW 264 cells by rinsing with fresh medium 24 hours later, and then with medium replacement and 3 more days of culture. The culture media or extracts of washed RAW 264 cells were tested for suppressor activity. The primed RAW 264 cells were lysed by 4 freeze-thaw cycles and cleared by centrifugation, and the resulting supernatant was tested on fibroblast (3T3) cell growth and wound healing in mice and for suppressor activity on T cells. Replication of 3T3 cells, as quantitated by uptake of [3H]thymidine, was reduced 75% when "suppressor" material from RAW 264 cells was added to 3T3 cultures and not when media or extracts of unprimed RAW 264 cells were added. Tensiometric measurements of wound breaking strength (full-thickness incised wounds) were reduced 31% by day 4 and 47% by postsurgical day 7 when "suppressor" RAW 264 extracts were instilled into wounds. Leukocyte cultures stimulated with phytohemagglutinin had a reduced uptake of [3H]thymidine (suppressed 90% to 95%) when exposed to primed RAW 264 extracts, whereas kidney cell culture lines were unaffected. The data obtained indicated that mastocyte (histamine)-induced suppressor factors are present for fibroblast activity as well as T-cell function.

Mice and rabbit models for oral and percutaneous absorption and disposition of amphoteric surfactant C31G

A topical antimicrobial agent (C31G), composed of amphoteric surfactants (alkyl betaines and alkyl amine oxides), had a significant (P less than 0.001) and concentration dependent rate of percutaneous absorption in mice and rabbits. Percutaneous absorption studies (3 concentrations for 3 exposure periods) in mice indicated that dermal interaction resulted in nonlinear changes for rate of penetration and transport as a function of exposure and concentration. Kinetic studies of absorption and disposition after oral dosing in mice with [3H]C31G were used to determine the body burden (0.21 g/kg of body weight) at a no effect level. Dermal penetration (P) and transport (T) resulting from percutaneous exposure at variations of time and dosage concentrations were shown to fit the equation T = a + k ln t. The regression coefficient k represents the characteristic change of T with exposure time (t). For low concentrations k equaled 1.89 and at the high concentration k equaled 2.68. This increase of T indicated the interaction of the agent with the dermal barrier at high concentrations. Dermal transport in the rabbit was less than one-fourth of that in the mouse. Excretion of C31G after oral or dermal dosing was predominantly renal at higher dosage levels, whereas fecal excretion dominated at the lowest dosage levels. The half-life of [3H]C31G in the mouse was 68 hours and 86 hours in the rabbit. Data and statistical methods allowed prediction of the effects of daily exposures

Characterization of deoxyribonucleic acid from cells infected with Aleutian disease virus

Viral DNA was extracted from Crandell feline kidney (CRFK) cells infected with Aleutian disease virus (ADV) and labeled with [ 3H ]thymidine. The sedimentation coefficient in alkaline sucrose gradients was 16S corresponding to a molecular weight of 1.5 X 10(6). The buoyant densities of DNA from infected and control cells were determined by isopyknic sedimentation in CsCl and NaI gradients. Two additional peaks of [ 3H ]DNA were found in infected cells, but not in control cell extracts. Fractionation of this DNA on hydroxylapatite indicated that the new peaks represented a single-stranded component, density 1.728 g/cm3, and a double-stranded component, presumed to be a viral replicative intermediate, density 1.718 g/cm3. The target antigen formation in CRFK cells was measured by gamma-irradiation of ADV and assayed for focus formation. The calculated size of ADV based on these measurements was 1.1 X 10(6). The H-1 parvovirus also was shown to have a size of 1.5 X 10(6) daltons for both antigen and plaque formation. The data indicated similarities existed between ADV and other autonomously replicating parvoviruses in most properties, except that less-than-unit length genome of ADV may be transcribed.

Effect of C31G, an antimicrobial surfactant, on healing of incised guinea pig wounds

An anti-infective surfactant composition (C31G) promoted healing of infected and noninfected wounds in guinea pigs. In this animal model, histologic features of wounds treated topically with C31G revealed an increased rate of wound closure associated with decreased inflammatory response and increased C31G fibroblast infiltration and epithelialization. The effect of C31G on fibrin formation, the initial event of wound healing, was compared with effects of anionic and cationic surfactants that delay healing. The surfactants had different effects on clotting time, platelet activation, and cross-linkage of the stabilized clot. Seemingly, C31G increased the protein cross-linking of fibrin in clots containing fibronectin.

Delayed wound healing in mice associated with viral alteration of macrophages

Mice acutely and chronically infected with Sendai virus had impaired healing of incisional wounds. This impairment could be overcome by instilling the macrophage-stimulators zymosan and glucan into full-thickness incised wounds, whereas levamisole, an immunomodulator, had no effect on tensile strength of these wounds (breaking strengths). Another commonly occurring murine virus, murine hepatitis virus, also reduced wound tensile strength in infected mice. However, the murine strain of herpes simplex virus, type 1, which caused greater morbidity, did not reduce tensile strength. Although measurements of wound length and wound breaking strength clearly showed the adverse effect of viral infection, histologic evaluation of wounds did not consistently reveal a similar change in composition of wound "cell aggregation centers" for mice infected with the Sendai and murine hepatitis viruses.

Modulation of early cellular events in wound healing in mice

Wound healing experiments were conducted in random-bred Swiss mice to determine the effect on antimicrobial surfactants and macrophage stimulators on wound measurements, histologic repair, and wound breaking strengths. In selection of mice, Sendai virus antibody-positive mice healed more slowly than did mice with no detectable titer to Sendai virus. Studies were conducted with Sendai virus-free mice that had C31G (an antimicrobial surfactant), alkyl amine oxide, zymosan, glucan, or phosphate-buffered isotonic saline solution instilled into full-thickness incised wounds. The early events in the repair process indicated a greater degree of inflammatory response comprised mainly of polymorphonuclear leukocytes with subsequent large numbers of monocytes in C31G and alkyl amine oxide-treated wounds. Although zymosan did not induce as large a number of monocytes, the degree of fibroplasia was as great as in wounds in which numbers were higher. The effect of zymosan could be blocked by the addition of N-alpha-p-tosyl-L-lysine chloromethyl ketone to wounds. Wound breaking strength 3 days after surgery was greatest for glucan-treated mice (134 +/- 37 g) whereas that in C31G-treated mice (77 +/- 31 g) was less than that of the controls (92 +/- 37 g). By day 7, there was no significant difference in breaking strength between control and glucan-treated wounds; however, C31G-treated wounds remained substantially weaker than control wounds.

Anti-deoxyribonucleic acid antibody associated with persistent infection of mink with Aleutian disease virus

Anti-deoxyribonucleic acid (DNA) antibody was quantitated in sera from mink infected with Aleutian disease virus (ADV). During the course of the disease after experimental infection, the amount of anti-DNA antibody increased 60% initially, but then decreased to an intermediate level when measured 2.5 months later. The percentage of serum immunoglobulin, however, steadily increased over 3.5-fold during this period, resulting in the characteristic gammopathy. Correlation between the level of anti-DNA antibody and hypergammaglobulinemia was demonstrated with sera from chronically infected mink. Competition experiments and use of labeled nucleic acids indicated that the immunoactivity was more specific for double-stranded DNA than single-stranded DNA or ribonucleic acid. Anti-DNA antibody was found in purified immunoglobulin from chronically infected mink. Differences in avidity of antibody to DNA among antisera that had the same equivalence point were found. Avidity of antibody for DNA increased during the course of the disease.

Lymphoproliferative diseases of fowl: characterization of transplantable G-B1 Marek's disease tumor cells in culture

A transplantable Marek's disease tumor, derived and maintained through in vivo passage in syngeneic G-B1 chickens, was established in cell culture and characterized. The cells (GBT cells) grew in suspension and appeared morphologically similar to other Marek's lymphoblastoid lines except for prominent nucleoli in GBT cells. The number of chromosomes increased during in vitro cultivation from near triploid to subtetraploid. Chromosome no. 3 was abnormally short. The GBT cells retained surface B1 histocompatibility antigen of the original tumor as well as Marek's disease tumor-specific surface antigen (MATSA); however, infectious Marek's disease virus was not detected by immunofluorescence, electron microscopy, inoculation into susceptible birds, or assay on susceptible cells in culture. Inoculation of as few as 100 cultured cells into syngeneic G-B1 chickens results in tumor formation at the inoculation site, with eventual death of the recipients.

Protides of the Mustelidae: immunoresponse of mustelids to Aleutian mink disease virus

Members of North American Mustelidae were tested for their response to inoculation with 10(6) infective doses of Aleutian disease virus. In subfamily Mustelinae, 3 species in the genus Mustela (M vision, M erminea, and M putorius) and 2 species in genus Martes (Ma pennanti and Ma americana) responded immunologically with some features resembling Aleutian disease in mink. In subfamily Mephitinae, only Mephitis mephitis responded, and others of the subfamily did not, nor did members of subfamilies Melinae and Lutrinae. The responses observed ranged from development of detectable antibody levels determined by counterimmunoelectrophoresis to histopathologic changes typical of Aleutian disease.

Properties of Aleutian disease virus assayed with feline kidney cells

Properties of Aleutian disease virus (ADV) were studied using feline kidney cells, line CRFK, to assay virus by the induction of nuclear antigen. ADV nuclear antigen was detected by immunofluorescent staining. Titers of virus obtained from mink spleens at 10-8 days after infection were usually between 10(3) and 10(5) infectious units per gram of spleen. ADV was purified by fluorocarbon extraction, differential centrifugation, biogel A-15 chromatography and CsCl equilibrium centrifugation. The molecular weight of the virus was estimated to be 3-5 X 10(5) daltons. The density of antigen-inducing virus in equilibrium CsCl gradients was 1.32--1.34 g/cm3. On velocity sucrose gradients, antigen-inducing virus had a sedimentation coefficient of approximately 110S. The virus was not neutralized by sera from chronically infected mink and ferrets and by sera from experimentally infected mink. ADV was resistant to ionic and nonionic detergents and lipid solvents. The titer of partially purified virus was reduced as much as 700-fold by proteolytic enzymes but not by DNase or RNase. The virus was inactivated slowly at 56 degrees C; the initial half-life was 90 minutes. It is concluded that the properties of ADV can be determined by assay in CRFK cells, thus facilitating virological study of the disease.

Lymphoproliferative diseases of fowl: JM-V leukemic lymphoblasts in cell culture

JM-V leukemic lymphoblasts were established in cell culture. The cultured cells (JM-VLC cells) were transplantable in young chicks and produced a disease indistinguishable from JM-V lymphoblastic leukemia as initiated by whole-blood inoculation. JM-VLC cells maintained a normal female karyotype through 13 passages in Rhode Island Red cockerels. With the use of JM-V antisera and antisera from birds with naturally occurring Marek's disease (MD), specific antigens were detected on the surfaces of living cells. Intracellular antigens were detected with anti-MD virus sera after cultivation for at least 1 day at 37 degrees C. In spite of the expression of MD antigens, the presence of herpesvirus particles associated with the cultured cells, and the occurrence of foci of multinucleated cells in kidney cultures from chicks inoculated with cellfree preparations of JM-VLC cells, the pathologic potential of the cultured cells was that of JM-V leukemia.

Expression of Aleutian mink disease antigen in cell culture

Infection of CRFK feline kidney cells with Aleutian disease vurus leads to production of virus-induced antigen(s) in the nucleus which could be demonstrated by the fluorescent-antibody technique. The number of fluorescent nuclei was lineraly dependent on the dilution of the inoculum, but rarely exceeded 20% of the cells. Aleutian disease nuclear antigen was only transiently detectable. The virus-induced antigen was detected after infection of cells of several divergent species; however, the CRFK line of feline kidney cells was the most susceptible. Inhibitor studies indicated that deoxyribonucleic acid synthesis, ribonucleic acid synthesis, and protein synthesis were required for viral antigen production. Cell growth was also a requirement for synthesis of viral antigen, An in situ radioimmune assay was used to measure binding of 125I-labeled mink anti-Aleutian disease virus to infected cells and competition with unlabeled sera. The system is suitable for quantitation of infectivity.

Lymphoproliferative diseases of fowl: chromosome breaks caused in lymphocytes by JM-V herpesvirus

Chromosome preparations were made of bone marrow cells and peripheral lymphocytes isolated from chicks that developed leukemia following infection with JM-V herpes-virus. Karyotypic analysis revealed a high frequency of chromosome breaks and aneuploidy, as well as some pulverization of chromosomes. The number of chromosome breaks began to increase at 2-3 days post infection, and by 5 days post infection it reached 12.7% of bone marrow cells and 17.2% of peripheral lymphocytes. Similarly, the number of aneuploid metaphase figures increased rapidly and reached 12% of bone marrow cells and 19% of peripheral lymphocytes at 5 days post infection. Some specificity was observed in the chromosomes that were affected.

Mobility of sodium dodecyl sulphate - protein complexes

Reduced and unreduced lysozyme aggregates formed by formaldehyde cross-linking comprise a set of model compounds for studying the effects of protein conformation on the electrophoretic mobilities of sodium dodecyl sulphate-protein complexes. The reduced aggregates were indistinguisable from normal proteins, but the unreduced aggregates migrated anomalously fast by about 14%. Contrary to expectations, plots of logarithm Rf versus Kr (retardation coefficient) failed to reveal an unusual conformation for the unreduced aggregates. Thus the anomalous mobility caused by several intramolecular disulphide bonds escaped detection by the above two diagnostic plots. Also included in this paper is a discussion of the implications of these results with regard to current models for sodium dodecyl sulphate-protein complexes.

Isolation of Aleutian mink disease virus by affinity chromatography

Affinity chromatography was used to isolate the Aleutian disease virus of mink. Dissociation of the immunoadsorbent-virus complex with 0.75 molar sodium chloride and then with a glycine-hydrochloride gradient released infective particles resembling picornaviruses. The elution profile suggests that two different types of virus-antibody complexes are formed, one dissociated by sodium chloride and another that requires glycine-hydrochloride in addition to sodium chloride for release of virus.

Mastocytoma and gastroduodenal ulceration. Gastric and duodenal ulcers in dogs with mastocytoma

Twenty of 24 dogs with mastocytoma had ulcers of the gastroduodenal mucosa. The ulcers were more frequent in the stomach, less frequent in the duodenum. Perforating ulcers caused death in 3 dogs. Vascular lesions were frequent in these dogs, and it was considered that the vascular alterations may have contributed to the gastroduodenal ulceration associated with mast-cell neoplasms.

'Nuclear' antigens and antinuclear antibodies in mink sera

Aleutian disease of mink is transferrable by cell-free extracts and is characterized by hepatitis, vasculitis, nephritis, and hypergammaglobulinaemia. Because of increasing evidence incriminating antigen—antibody complexes in vasculitis disorders, the presence of nuclear antigens and antinuclear antibodies in mink sera was investigated.

Serum pools as well as individual serum specimens were obtained from uninfected mink, mink with experimentally induced Aleutian disease, mink with spontaneous Aleutian Disease, all of genotype Aa as well as from `normal' mink of similar age from colonies without Aleutian disease.

The serum pool from mink before and after experimentally induced Aleutian disease appeared to contain `nuclear' antigens detectable by rabbit anti-DNA antibodies in complement fixation and precipitin tests. The protein-free extracts of these serum pools gave strong reactions for deoxypentose in the diphenylamine tests. These serum pools also were shown to contain antinuclear antibodies by the immunofluorescence tests on human leucocyte nuclei and in precipitin tests against single strand calf thymus DNA. Sera from individual mink were similarly shown to contain `nuclear' antigens and antinuclear antibodies. The incidence and quantity of antigens and antibody detected were much greater in sera from mink after experimentally induced disease than in sera taken from mink before inoculation. The presence of `nuclear' antigens and antinuclear antibodies did not correlate with the degree of hypergammaglobulinaemia. Sera from `normal' mink in colonies without overt disease had neither antigens nor antibodies detectable in precipitin tests. Sera from mink with spontaneously acquired Aleutian disease had a high incidence of `nuclear' antigens and anti-DNA antibodies detectable in precipitin tests.

The `nuclear' antigens were detectable in Ouchterlony precipitin tests by specific rabbit anti-DNA antibodies. The precipitins formed lines of partial identity with those between the rabbit anti-DNA antibodies and single strand calf thymus DNA. However, the antigens in mink sera were not destroyed by prior incubation with DNAse which had been the case with DNA antigens detected in some human and mouse sera.

The antinuclear antibodies were detected in immunofluorescence tests using specific antibodies to mink γ-globulins, were shown to fix complement with single strand calf thymus DNA, but not with DNA that had been digested with DNAse, and formed precipitins with single strand calf thymus DNA which showed complete identity with precipitins formed by rabbit anti-DNA antibodies. Evidence for the simultaneous presence of `nuclear' antigens with antinuclear antibodies in the serum from mink with Aleutian disease was frequently evident. This observation is consistent with the hypothesis for the pathogenetic role of antigen-antibody complexes.

Aleutian disease of mink has certain clinical pathological and serological similarities with disease in New Zealand Black mice and in man with systemic lupus erythematosus. Since Aleutian disease of mink and disease of New Zealand black mice may both be examples of `slow virus' infections, a similar aetiology should be considered for certain autoimmune diseases of man, e.g. systemic lupus erythematosus.

Cutaneous lymphomatosis in a boxer dog. Pathologic and biochemical observations

A 9-ycar-old boxer dog had rapidly progressive cutaneous lymphomatosis. There were pulmonary metastases, marked peripheral eosinophilia, eosinophilic infiltration of the cutaneous lesions, and a moderate heterogeneous elevation of the serum immunoglobulins, especially those with gamma mobility. The disease had similarities to viral-induced cutaneous leukosis of chickens and cattle.