Angled abutments result in increased or decreased stress on surrounding bone of single-unit dental implants: A finite element analysis

The influence of angled abutments on stress is a matter of debate. It is widely accepted that increased stress on implants and bone has been associated with the use of angled abutments.However, comparisons of clinical success rates of implants restored with angled and straight abutments indicate no significant differences. The aim of the present study was to determine whether angled abutments could result in decreased stress on surrounding bone of single-unit dental implants. By means of finite element analysis (FEA), four simplified models were designed to simulate clinical scenarios in which that implants were placed in an ideal axial position or at an angled position. Each implant was paired with a straight or angled abutment. A simulated occlusal load of 100 N was applied along the vertical axis of the jawbone. The von Mises stress and strain were recorded for each model. The numerical results showed that angled abutments resulted in decreased stresses when implants were not placed in ideal axial position. The present study identified by means of FEA that angled abutments could result in decreased stress on the supporting bone of implant system and may provide some clues to resolve the debate regarding the influence of angled abutments.     

Enhancement of the immunogenicity of the maize rough dwarf virus outer shell with the cross-linking reagent dithiobis(succinimidyl)propionate

Injection into rabbits of native or glutaraldehyde (GA)-treated intact particles of the fijivirus maize rough dwarf virus (MRDV) failed to yield antibodies to the outer shell of the virus. After fixation of the particles with the cross-linking reagent dithiobis(succinimidyl)propionate (DSP), antisera were obtained reacting with the outer shell of MRDV (both DSP-fixed and unfixed) to a titre of $\text{1}\text{1024}$ in immunoelectron microscopic decoration tests, but giving no reaction with another fijivirus, oat sterile dwarf virus, whose subviral particles are known to be unrelated to those of MRDV. Further fixation of the DSP-fixed particles with GA did not appear to enhance immunogenicity. Stabilization with DSP could have further application with viruses the instability of which renders them poor immunogens.     

Immune function in congenital osteopetrosis: Defective lymphocyte function in microphthalmic mice

Osteopetrosis is a prominent feature of a congenital mutation described in microphthalmic mice and is thought to be due to defective osteoclast function which causes a generalized lack of bone resorption. Reversal of defective bone resorption in osteopetrotic mutants has been achieved by hematopoietic cell trans-plantations; and conversely, defective bone resorption has been transferred to normals by hematopoietic cells from osteopetrotic littermates. This suggested that osteopetrotic mutants might also demonstrate defective immune functions which could in turn be related to the lack of normal bone resorption. To that end, aspects of $\text{in}$$\text{vitro}$ lymphocyte function in microphthalmic mice were compared to those of their phenotypically normal littermates. There was a significant diminution in the proliferative response of splenocytes to mitogens in microphthalmic mice. Microphthalmic splenocytes also were less responsive in an $\text{in}$$\text{vitro}$ assay which measured the capacity to form antibody forming cells.     

Immunological recognition of cuticular transplants in insects

Transplantation of allogeneic and xenogeneic cuticle onto the American cockroach, $\text{Periplaneta americana}$, was carried out in order to compare the specificity of immune recognition of these ‘skin grafts’ with that of implanted tissues. In order to facilitate interpretation of results, the technique of transplanting cuticle from nymphal donors onto nymphal recipients was adopted - if donor subcuticular epidermis is not recognised as ‘foreign’, it will grow, fuse with the recipient's epidermal sheet and will be stimulated by the recipient's hormonal signals to produce new cuticle of donor type at the next moult. Neither allogeneic cuticle nor xenogeneic cuticle from $\text{Blatta orientalis}$ were recognised as foreign by the immune system of $\text{P. americana}$ - dark patches of $\text{Blatta}$-type cuticle were produced at the graft site post-moult. Conversely, xenogeneic cuticle of $\text{Blaberus craniifer}$ was not visible post-moult. These results corroborate those from implantation studies, that allogeneic tissues from $\text{P. americana}$ and xenogeneic tissues from $\text{B. orientalis}$ are immunologically compatible with $\text{P. americana}$, whereas xenogeneic tissue from $\text{Blaberus craniifer}$ is incompatible. Whether this incompatibility is immunological or ‘positional’ has not yet been determined; the observation that xenografts from $\text{Nauphoeta}$$\text{cinerea}$ do not reappear on $\text{P. americana}$ post-moult, whereas 50% of $\text{N. cinerea}$ implants are not recognised as ‘foreign’, suggests that ‘positional incompatibility’ (i.e. the signals responsible for formation of cuticular pattern are incorrect for the donor epidermis) may also play an important part in the rejection of $\text{N. cinerea}$ cuticular grafts.     

Lectins and antibodies as molecular probes of molluscan hemocyte surface membranes

A variety of carbohydrate-specific lectins and antigen-specific antibodies have been employed to assess the occurrence and topographic distribution of surface membrane determinants on hemocytes of two stocks of the snail, $\text{Biomphalaria}$$\text{glabrata}$, which differ in their susceptibilities to larval blood fluke ($\text{Schistosoma}$$\text{mansoni}$) infections. Using fluorescence labeling methods, several “classes” of hemocyte membrane components have been identified. These include (1) macromolecules, primarily glycoproteins, possessing reactive sites for concanavalin A and $\text{Ricinus}$$\text{communis}$ agglutinin, (2) snail hemolymph or hemolymph-like determinants, (3) fibronectin-like membrane components, and (4) surface determinants with structural similarities to murine Thy-1 antigen. No qualitative differences in surface molecular composition were observed between hemocytes of the two $\text{B}$. $\text{glabrata}$ stocks, although the broad reaction specificity of most of the probe reagents employed preclude the detection of small or minor differences in hemocyte membrane structure. Results of these investigations indicate that snail hemocytes possess a complex array of surface membrane components some of which appear to be shared with higher vertebrate species.     

Immunoglobulin-secreting cells in various maternal lymphoid tissues during syngeneic and allogeneic murine pregnancy

The effects of syngeneic (CBA×CBA) and allogeneic ($\text{CBA}\text{×}\text{C}\text{57}\text{B}\text{1}$) pregnancy on immunoglobulin (Ig)-secreting cells in various maternal organs/tissues have been investigated by using the protein A plaque assay. The following organs/tissues were examined: $\text{a}$) spleen, $\text{b}$) cervical nodes, $\text{c}$) inguinal nodes, $\text{d}$) mesenteric nodes, $\text{e}$) paraaortic (uterus-draining) nodes, $\text{f}$) Peyer's patches, and $\text{g}$) bone marrow (femur). The changes observed were similar and of the same magnitude in all pregnant animals, irrespective of the type of mating. At mid-gestation (day 14) a distinct increase in Ig secretors was observed, predominantly in the spleen. At the end of pregnancy (day 20) the para-aortic nodes contained dramatically increased numbers of plaque forming cells. A slight increase in both IgM and IgG-secreting cells was also seen in bone marrow at the very end of pregnancy, while Peyer's patches and the nodes of neck and legs appeared to be unaffected throughout the period of gestation.     

Leukocyte histamine release in Hymenoptera-allergic patients. Correlation with skin test reactivity and changes following hyposensitization therapy

We have studied 46 Hymenoptera-allergic patients and 11 nonallergic controls by grading the severity of their sting reaction, determining their skin test reactivity, and performing human leukocyte histamine release with a commercial mixed stinging insect extract. A significant correlation was found between increasing severity of sting reaction and increasing skin test reactivity (p < 0.001). In $\text{41}\text{46}$ allergic patients from 15 to 100 per cent release of total cellular histamine occurred, whereas in the 11 nonallergic controls no greater than 10 per cent release of total cellular histamine was observed. Skin test reactivity correlated significantly with cell sensitivity in the allergic patients (p < 0.001). Following hyposensitization therapy, cell sensitivity generally did not change, but significant increases in antigen-neutralizing capacity (A.N.C.) of allergic serum did occur in $\text{11}\text{15}$ Hymenoptera-allergic patients.     

Hemocyte lysate enhancement of fungal spore encapsulation by crayfish hemocytes

Crayfish hemocytes exhibited a stronger encapsulation reaction to fungal blastospores of $\text{Beauveria}$$\text{bassiana}$ coated with hemocyte lysate, than to blastospores treated with plasma or buffer, indicating an opsonic function of hemocyte lysate proteins. Five proteins of the prophenoloxidase activating system in the hemocytes were attached to foreign surfaces (including the blastospores) after activation and it is suggested that these attaching proteins (one being phenoloxidase) are responsible for the opsonic function of the hemocyte lysate on crayfish blood cells.     

Evaluation of Hymenoptera-sting sensitivity with deliberate sting challenges: inadequacy of present diagnostic methods

We administered deliberate sting challenges to 21 patients, five of whom had histories of large local (LL) reactions and 16 of whom had previous systemic (SYS) reactions to stings. Eleven had been treated previously with whole-body extract, but none had received venom immunotherapy. Immediately before sting challenges with honeybees, wasps, yellow jackets, yellow hornets, and white-faced hornets, we performed skin tests and measured serum IgE antibody levels with venoms from these five insects. In addition, we measured IgG antibody levels to honeybee, yellow jacket, and white-faced hornet venoms. In the LL group, $\text{14}\text{21}$ skin tests were negative, but in the SYS group $\text{30}\text{34}$ skin tests were positive prior to the deliberate sting. IgE antibody levels (expressed as percent of binding compared with serum from a nonsensitive individual) ranged from 63% to 789% and 66% to 801% for the LL and SYS groups, respectively. IgG antibodies ranged from <5 to 332 U/ml, and levels were similar for the LL and SYS groups. Fifty-five sting challenges were administered; seven generalized reactions were induced and occurred only in the SYS group. Seven individuals (three LL, four SYS) who tolerated the first series of stings returned for a second series of sting challenges with the same insects. Of these seven, $\text{10}\text{15}$ skin tests were now positive in the LL group; $\text{10}\text{12}$ skin tests were now positive in the SYS group. IgE antibody levels ranged from 103% to 737% and 85% to 2389% for the LL and SYS groups, respectively, prior to the second series of sting challenges; IgG antibody levels were again similar in both groups. All repeat challenges were tolerated without generalized reactions. No in vitro or in vivo test predicted with certainty the clinical immune status of a sting-sensitive person.     

Allergy diagnosis with the radioallergosorbent test: A comparison with the results of skin and provocation tests in an unselected group of children with asthma and hay fever

The radioallergosorbent test (RAST) has been used for in vitro diagnosis of asthma and hay fever in children as an integrated part of the routine procedure for allergy diagnosis. A positive RAST test was combined with a positive prick test in $\text{196}\text{235}$ (80 per cent) tests and with a positive provocation test in $\text{163}\text{182}$ (90 per cent) tests. When the provocation test was positive to dry pollen, the stock solution ($\text{1}\text{10}$ w./v. or 10,000 PNU) of the allergen extract RAST was quite often negative, a fact that explains the lower degree of correlation for a negative RAST test. A comparison between the prick test and the provocation test revealed a high proportion, $\text{54}\text{146}$ (37 per cent), of positive prick tests that could not be confirmed by the provocation test. RAST is a simple, reliable test for IgE antibodies that is very useful for in vitro diagnosis of atopic allergy on a routine basis. RAST is harmless and less traumatic than skin testing and therefore suitable for use even on very small children. The information obtained on the patient's hypersensitivity is more relevant than that from regular skin testing, probably comparable to skin test titration with selected allergens but not quite as good as provocation testing of the shock organ involved. Whenever a provocation test cannot be performed for each suspected allergen, an RAST test, possibly completed with a prick test, is recommended.     

Histologic studies of human skin test responses to ragweed, compound 48-80, and histamine

The patterns of mast cell and eosinophil changes at the site of intradermal injection of ragweed, compound $\text{48}\text{80}$, and histamine were studied by histologic techniques. Dermal biopsies of 23 ragweed skin test-positive subjects revealed increasing numbers of eosinophils and decreasing numbers of mast cells over a 240 minute period following injection of antigen. The eosinophil response began in the periappendigeal areas, extended into the interstitium, and occurred in sites with depressed wheal reactions in hydroxyzine-treated subjects. These cellular patterns did not occur at ragweed skin test sites in nonatopic subjects. However, compound $\text{48}\text{80}$ induced similar eosinophilic responses in both atopics and nonatopics. Histamine injection was followed by no eosinophilic or mast cell changes. These findings support the hypothesis that eosinophil responses in reagin-mediated reactions may occur secondary to release of a mediator other than histamine of mast cell origin.     

角度基台生物力学影响的研究现状

角度基台对种植体周围骨组织应力分布的影响是一个有争议的问题,目前比较一致接受的观点是在种植修复中使用角度基台会增加种植周围骨组织不利的应力分布。但是临床观察确没有发现角度基台对种植修复带来不良的影响。总结角度基台的临床应用及其影响、角度基台相关生物力学研究,发现角度基台的应用不会带来不良的临床影响,但基台角度变化确实会给种植体周围组织应力分布带来一些变化,增大和减小种植体周围组织应力分布都是可能的。因此,如何合理利用角度基台带来有利的应力分布是以后口腔种植临床研究的一个方向。     

In vivo and in vitro comparison of fire ant venom and fire ant whole body extract

Thirty-four patients with a history of immediate hypersensitivity to the sting of the imported fire ant were evaluated in a study designed to compare the diagnostic usefulness of fire ant whole body extract (WBE) preparations with that of fire ant venom (IFAV). Ninety-one percent ($\text{31}\text{34}$) of the hypersensitive patients skin tested with IFAV at a maximal concentration of 1:5 × 10³, $\text{v}\text{v}$, demonstrated a wheat equal to or greater than the histamine control. Fifty-three percent ($\text{18}\text{34}$) of the group were skin test positive to a WBE preparation. When the criteria for a positive skin test were relaxed, 82% of the hypersensitive group could be identified with the IFAWBE. A comparison of skin test results in sensitive patients revealed variability in the sensitivity of the WBE preparations utilized in the study. Leukocyte histamine release demonstrated a dose-response release of histamine with both IFAV and SIWBEa preparations. Specific venom antisera produced in rabbits identified a precipitin line of common identity in a gel-diffusion system containing IFAWBE and IFAV. This finding was verified by the competitive inhibition of IFAWBE with IFAV in a solid-phase radioimmunoassay system. Fire ant WBEs contain venom constituents and are effective diagnostic agents in up to 82% of patients with hypersensitivity to the sting of the imported fire ant. Marked variability in the responsiveness of sensitive patients to different WBE preparations mandates standardization of these diagnostic preparations.     

Role of immediate food hypersensitivity in the pathogenesis of atopic dermatitis

Twenty-six children with atopic dermatitis and markedly elevated serum IgE concentrations were evaluated for clinical evidence of hypersensitivity to foods with double-blind placebo-controlled food challenges. Selection of foods for challenges was based on positive prick skin tests (>3 mm wheal) or a convincing history. At least one positive skin test to a food antigen was found in $\text{24}\text{26}$ patients. A total of 111 double-blind placebo-controlled challenges were performed in these children after suspect foods were eliminated from their diets for 10 to 14 days. There were 23 positive challenges in 15 children, 21 of which manifested as cutaneous symptoms, primarily pruritus and an erythematous macular and/or maculopapular rash involving 5% (or greater) of the body surface. In all, 14 children (54%) developed cutaneous symptoms after food challenges. All symptoms occurred within 10 min to 2 hr of challenge; nasal symptoms, mild wheezing, and gastrointestinal symptoms were seen in some children. No symptoms occurred in 104 placebo challenges. There were $\text{86}\text{111}$ clinically insignificant positive skin tests (77%) and three false-negative skin tests. These studies demonstrate that in some children with atopic dermatitis, immediate food hypersensitivity can provoke cutaneous pruritus and erythema, which leads to scratching and subsequent eczematoid lesions.     

The influence of chronic Ostertagia circumcincta infection on the skeleton of growing sheep

The effect on the skeleton of growing sheep of daily infection with small numbers of Ostertagia circumcincta larvae was investigated in 2 experiments. In the first, groups of 6 sheep aged $\text{2}\text{1}\text{2}$ to 3 months were given either 1000, 3000 or 5000 larvae a day for 8 weeks. In the second, 4000 larvae a day were given for 14 weeks to 3- to 4-month-old sheep; controls were slaughtered initially, fed ad-libitum or pair-fed. In both experiments tibia, lumbar vertebrae, rib and costochondral junction were examined histologically and chemically and the concentrations of certain serum constituents measured.Although histology generally revealed few bone abnormalities other than osteoporosis in those sheep in which parasitism caused greatest depression of appetite, chemical analyses showed that infected sheep deposited less than half the bone ash of normal sheep. This was due to a reduction in bone size, although the density of bone matrix and its degree of mineralization were also reduced. These changes are tentatively ascribed to an induced energy or protein deficiency.     

Soluble peptidoglycan fragments stimulate antibacterial protein synthesis by fat body from larvae of Manduca sexta

Both hemocytes and fat body from larvae of $\text{Manduca}$$\text{sexta}$, which have been injected with inducers of antibacterial protein synthesis, contain immunoreactive lysozyme. However, fat body is a richer source and has been demonstrated to synthesize and release lysozyme and cecropin-like peptides (bactericidins) $\text{in}$$\text{vitro}$. Fat body secretion of lysozyme and bactericidins is stimulated by addition of soluble peptidoglycan fragments to culture medium. The rate of lysozyme secretion by fat body varies as a function of peptidoglycan inducer concentration. These data are consistent with the hypothesis that, $\text{in}$$\text{vivo}$, bacteria must be phagocytized and partially degraded (processed) by hemocytes to generate a signal (peptidoglycan) that subsequently induces antibacterial protein synthesis by fat body.     

Exogenous estradiol and sexual receptivity in photoinhibited female Lemur catta.

Nine Lemur catta females whose ovarian cycles had been inhibited by exposure to long daylength (18L:6D) for 220 days were implanted with Silastic tubules (4.0 cm×0.132 in. i.d.) containing estradiol-17β (E₂) while caged continuously with a male. Radioimmunoassay demonstrated a transitory peak (261.8 pg/ml ± 2.42 SEM) in mean plasma E₂ concentration $\text{4-}\text{1}\text{2}$ hr after insertion of implants that was followed by relatively constant hormone titers (approximately 100 pg/ml) until removal of implants. Five females received an ejaculation after a decline in plasma E₂ concentration. These data demonstrate that a consistent, predictable and reproducible plasma estradiol hormone profile follows insertion of E₂ implants. These data also lend support to the hypothesis that declining estradiol titers activate sexual receptivity in L. catta.     

Kinin formation in hereditary angioedema plasma: evidence against kinin derivation from C2 and in support of “spontaneous” formation of bradykinin

Hereditary angioedema (HAE) is due to a functional deficiency of the inhibitor of the activated first component of complement ($\text{C}\text{1}$ INH). This abnormality is thought to be responsible for the generation of a kininlike peptide in HAE plasma that is derived from the second component of complement (C2). Specifically, a combination of C2 cleavage by $\text{C}\text{1s}$ and C2 fragment cleavage by plasmin has been reported to generate a kinin that is distinguishable from bradykinin. We have attempted to generate this peptide by activating the classical complement pathway by incubation of plasma with immune complexes and then adding plasmin or by incubating purified $\text{C}\text{1s}$ with C4 and C2 and then adding either plasmin or trypsin. We performed a total of 13 experiments, and in no case was a kininlike molecule generated as assessed by contraction of the estrus rat uterus. However, incubation of EDTA-treated HAE plasma at 37 °C for time intervals up to 1 hr progressively generated a smooth muscle-contracting activity. This activity was resistant to tryptic digestion but was destroyed after incubation with carboxypeptidase B, an inhibition profile consistent with that of bradykinin. We therefore propose that bradykinin alone, or in combination with other factors heretofore unrecognized, might be responsible for the swelling that is characteristic of hereditary angioedema.     

Maturation of transplantation antigens in Ambystomamexicanum

Both juvenile (14–16 week) and adult (18 month) $\text{Ambystoma}$$\text{mexicanum}$ reject skin allografts from adult $\text{Ambystoma}$ more speedily than they reject such grafts from juvenile axolotls. Donor-specific histocompatibility antigen, prepared from splenocytes, is more effective in inhibiting adult host splenocyte migration when the antigen is prepared from spleen cells from adult, rather than from juvenile $\text{Ambystoma}$. The thymus is fully developed in juvenile $\text{Ambystoma}$, suggesting that the delayed kinetics of rejection of juvenile allografts reflects immaturity in the expression of histocompatibility antigens to donor skin cells.     

Comparative studies on haemagglutinins and haemolysins in an annelid and a primitive crustacean

Biological properties of haemagglutinins and haemolysins in the annelid $\text{Eisenia}$$\text{foetida}$ and in the primitive crustacean $\text{Triops}$$\text{cancriformis}$ were investigated using rabbit erythrocytes. A great variability has been found within each species: while some animals possess agglutinins, others have lysins, or both, or none. The agglutinins seem to be protein or protein-like substances and are heat-labile; on the other hand, the lytic factors are not proteins and are very heat stable. Agglutinins of both these species investigated show greater discrimination than lysins between erythrocytes of different vertebrates and in some circumstances the agglutinins adhere to the erythrocytes without visible clumping. Lysins do not remain on target erythrocytes after reacting, and their activity is inhibited by agglutinins.