The homogenous alternative to biomineralization: Zn- and Mn-rich materials enable sharp organismal "tools" that reduce force requirements.

We measured hardness, modulus of elasticity, and, for the first time, loss tangent, energy of fracture, abrasion resistance, and impact resistance of zinc- and manganese-enriched materials from fangs, stings and other "tools" of an ant, spider, scorpion and nereid worm. The mechanical properties of the Zn- and Mn-materials tended to cluster together between plain and biomineralized "tool" materials, with the hardness reaching, and most abrasion resistance values exceeding, those of calcified salmon teeth and crab claws. Atom probe tomography indicated that Zn was distributed homogeneously on a nanometer scale and likely bound as individual atoms to more than » of the protein residues in ant mandibular teeth. This homogeneity appears to enable sharper, more precisely sculpted "tools" than materials with biomineral inclusions do, and also eliminates interfaces with the inclusions that could be susceptible to fracture. Based on contact mechanics and simplified models, we hypothesize that, relative to plain materials, the higher elastic modulus, hardness and abrasion resistance minimize temporary or permanent tool blunting, resulting in a roughly 2/3 reduction in the force, energy, and muscle mass required to initiate puncture of stiff materials, and even greater force reductions when the cumulative effects of abrasion are considered. We suggest that the sharpness-related force reductions lead to significant energy savings, and can also enable organisms, especially smaller ones, to puncture, cut, and grasp objects that would not be accessible with plain or biomineralized "tools".

Dominant nonresponsiveness in the induction of autoimmunity to liver-specific F antigen.

The liver-specific F antigen, although not an autoimmunogen, can induce the production of autoantibodies in responder strains. The ability to respond is under the control of two genes, one linked to the H-2 locus of mice, the other not. Responders possessing both genes produce high anti-F titers, while the H-2-linked gene alone permits a significant but low antibody response. (Responder X nonresponder) F1 hybrids derived from parents possessing identical F molecules are nonresponders, in contrast with the dominance of responsiveness in Ir gene systems. The presence of the H-2 locus from nonresponders appears involved in the inability to respond. This is discussed in terms of self-tolerance and suppression.

Variations in the responses of C57BL-10J and A-J mice to sheep red blood cells.

In response to repeated injections of sheep red blood cells, C57BL/10J mice produce predominantly 19S antibody in increasingly higher amounts, while A/J mice initially produce 19S antibody and then switch to produce increasing 7S antibody titers. In an F(1) generation all mice responded like the C57BL/10J mice. Backcross data implied genetic control involving at least three loci.

DR-positive maternal engrafted T cells in a severe combined immunodeficiency patient without graft-versus-host disease.

A 2 1/2-year-old male infant with severe combined immunodeficiency was documented by HLA typing and the presence of a female karyotype in the few spontaneously dividing cells to have an intrauterine-derived maternal lymphocyte graft. The presence of DR antigens on the engrafted maternal E rosette-forming T cells was demonstrated by both cytotoxicity and immunofluorescence techniques using both conventional and monoclonal antihuman DR antisera. These DR antigens were of the same allospecificity, DR4, as the mother's peripheral blood B cells. The patient's B cells and monocytes expressed DR alloantigens DR4 and DR3, corresponding to his genotype. Although fresh maternal lymphocytes react strongly in vitro against patient non-T cells, the engrafted maternal T lymphocytes no longer show this activity. Furthermore, clinical evidence suggesting mild graft-versus-host disease was completely resolved by the end of his first year. The presence of the DR-positive maternal cells may reflect the survival of a group of activated suppressor cells mediating graft tolerance of host tissue.

The mechanism of intraocular pressure rise during cyclocryotherapy.

PURPOSE: Intraocular pressure (IOP) spikes that occur during cyclocryotherapy for advanced glaucoma may further injure the already damaged glaucomatous optic nerve and be responsible for visual impairment that may occur after this treatment. The authors investigated the mechanism of pressure rise to see whether it can be avoided and thus prevent further optic nerve injury. The authors postulated that intraocular ice forms during the cryo procedure and causes the pressure changes. METHODS: Intraocular pressure was monitored using a pneumatonometer during 15 cryocycles of four patients with advanced glaucoma and 21 cryocycles of five normal rabbits. A simple thermal model was developed to analyze the relation between volume expansion and pressure rise in the eye. The physical effect of freezing rabbit eye structures was investigated in vitro. RESULTS: The largest pressure spikes observed during the cryocycles in this work were increases of 32 mm Hg for humans and 25 mm Hg for rabbits. The mean value of the IOP immediately before and after the cryo freezing stage was 53 +/- 1 and 68 +/- 2 mm Hg, respectively, for humans and 22 +/- 1 and 32 +/- 1 mm Hg for rabbits. The parameters of the thermal model were determined from the observed IOP spikes. Calculated thaw times were consistent with measured times for return to precryo IOPs. In vitro cryoapplication (rabbit eye) showed the formation of an ice ball internal to the eye. CONCLUSIONS: Volumetric increase of the intraocular content related to the formation of an ice ball in the eye, is the mechanism of pressure spikes during cyclocryotherapy. Because this complication is unavoidable, other cyclodestuctive methods may be more prudent, particularly in patients with advanced glaucoma.

Plasminogen activator activity in tears after excimer laser photorefractive keratectomy.

PURPOSE: To quantify changes of plasminogen activator activity in tear fluid during corneal re-epithelialization after excimer laser photorefractive keratectomy (PRK). METHODS: Tear samples were collected with glass capillaries from 77 eyes of 42 patients immediately before and immediately after PRK treatment and on postoperative days 3 and 5. In 20 patients, the contralateral eye was similarly sampled to serve as control. Plasminogen activator activity in the tear samples was measured by a spectrophotometric method using human plasminogen and chromogenic peptide substrate, D-valyl-L-leucyl-L-lysine-p-nitroanilide (S-2251). RESULTS: In tears of all eyes that underwent PRK, the plasminogen activator activities were lower immediately after PRK than were the preoperative values. For patient eyes with normal wound healing, tear plasminogen activator activities were significantly elevated above the preoperative level on the third postoperative day and then returned to the preoperative level by the fifth postoperative day. In contrast, tear plasminogen activator activities remained low through the third postoperative day in all (six) eyes in which haze developed after 3 to 6 months. The contralateral control eyes showed no appreciable change in plasminogen activator activity over the 5-day period. CONCLUSIONS: Plasminogen activator activity levels measured in tears of excimer laser PRK-treated eyes may serve as a predictor of wound healing. Extended low levels of plasminogen activator activity through the third postoperative day correlate with the development of corneal healing abnormalities (haze). The low plasminogen activator activity could be not only an accompanying sign but also a cause of defective corneal wound healing.

Cytotoxic effector cells against HLA antigens in strong linkage disequilibrium: identification of a strong, new CML determinant.

Three sets of cytotoxic effector cells were generated against the A1, B8, DR3 haplotype using haploidentical individuals in three different families. The three sets of effector cells generated against this haplotype showed excellent reproducibility testing, strong cytotoxicity against their specific targets, low autologous kill, and segregation with the sensitizing haplotype within the family. When tested against a panel of cells bearing all combinations of the A1, B8, DR3 antigens, a hierarchy of contribution of the individual HLA antigens as CML target determinants was seen. A new strong target cell determinant was identified by cytotoxicity with one of the effector cells not explicable in terms of the A1, B8, DR3 antigens or known HLA cross-reactivity. A family study demonstrated that this determinant clearly segregates with HLA. The success of this approach in defining new CML determinants may result from the generation of effector cells across a single haplotype in strong linkage disequilibrium or from the presentation of CML determinants in the context of self.

Frequency of alloantibodies reacting with PHA-activated T lymphocytes, unexplainable by known HLA activities.

Two hundred and three sera obtained from multiparous women were screened to determine the frequency of the appearance of antibodies reactive with PHA-activated T lymphocytes, but not with resting B or T cells from the same donor. The panel of cells on which the sera were tested consisted of lymphocytes from 38 unrelated donors known to be homozygous at the HLA-D locus. Forty-two sera were shown to react uniquely with PHA-activated T cells. The reactivities of these sera could not be explained in terms of the defined HLA-A,-B,-C, or DR antigen specificities on the panel cells, nor on the basis of known cross-reactivities among these antigens. Most of the antisera showed strong cytotoxicity with the activated T cells. Such sera may define antigens presented to the maternal immune system during differentiation and development, which are not expressed on adult T cells unless they are activated.

Validity of pulsatile ocular blood flow measurements.

The determination of average net pulsatile ocular blood flow form measurements of the intraocular pressure (IOP) pulse is based upon 1) an accurate measurement of IOP and its time variation; 2) a knowledge of the relation between the volume of the living eye and its IOP; 3) a physical model for the flow of blood through the eye: and 4) a concept of steady venous outflow from the eye. Each of these premises needs to be examined. The present analysis assesses the validity of the pneumatic tonometer for measuring the pressure in a flowing column of gas that is directed toward a thin membrane that is in contact with the surface of the cornea. The pressure of this stream of gas exerts a force against the cornea that depresses the corneal surface against the opposing force of the IOP. The balance of these forces and the resultant effect on the tonometer pressure sensor is described by the theories of elasticity, thermodynamics and fluid mechanics. In this treatment, differential equations are solved for the elastic deflections of the cornea subject to the opposing intraocular and tonometer pressures. This permits the pressure in the chamber of the pneumatic tonometer to be related through first principles to the IOP. The response of the tonometer pressure sensor to a range of IOPs (5-60 mmHg) is obtained, as well as the dynamical response of the tonometer to IOP oscillations. The conclusion is that the pneumatic tonometer provides a high fidelity, noninvasive measure of the IOP and its time variation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effect of latanoprost on pulsatile ocular blood flow in normal eyes.

PURPOSE: To determine the effect of an acute dose of 0.005% latanoprost on intraocular pressure and pulsatile ocular blood flow in normal eyes. METHODS: Nineteen volunteers received a single dose (two drops) of latanoprost 0.005% in one eye and placebo in the fellow control eye, randomized and masked to the observer. Intraocular pressure, perfusion pressure, pulsatile ocular blood flow, and systemic circulatory parameters were measured before and 8 hours after dosing. RESULTS: The mean (+/- SE) intraocular pressure, perfusion pressure, and pulsatile ocular blood flow before treatment were 17 +/- 1 mm Hg, 46 +/- 3 mm Hg, and 13 +/- 1 microl per second, respectively, in both the treated and control eyes. The mean intraocular pressure reduction was 4.9 and 2.1 mm Hg (28% and 12%) in the treated and fellow eye, respectively. The mean perfusion pressure increase was 5.6 and 2.8 mm Hg (12% and 6%) in the treated and fellow eye, respectively. The mean pulsatile ocular blood flow increase was 2.7 and 0.2 microl per second (20% and 1%) in the treated and fellow eye, respectively. The treated eye change in pulsatile ocular blood flow was not correlated to the change in perfusion pressure. Simultaneous reduction of intraocular pressure and increase or no significant change in pulsatile ocular blood flow occurred in 15 of 19 (79%) of the treated eyes. The systemic blood pressure and pulse rates remained in normal ranges over the 8-hour period. CONCLUSION: In this study, topical latanoprost significantly reduces intraocular pressure and increases ocular blood flow in normal eyes 8 hours after dosing. These effects of latanoprost may be beneficial in the management of glaucoma patients.

Reproducibility of topographic measures of the glaucomatous optic nerve head.

AIMS/BACKGROUND: Laser scanning tomography provides an assessment of three dimensional optic disc topography. For the clinical purpose of follow up of glaucoma patients, the repeatability of the various measured variables is essential. In the present study, the reproducibility of morphometric variables calculated by the topographic scanning system, TopSS (Laser Diagnostic Technology, San Diego, CA) was investigated. METHODS: Two independent measurements (30 minutes apart) each consisting of three complete images of the optic disc were performed on 16 eyes of 16 glaucoma patients using a TopSS. The instrument calculates 14 morphometric variables for the characterisation of the optic disc. RESULTS: From the two tailed paired tests, all variables were seen to have good reproducibility. However, correlation and regression analyses showed that only the three variables, volume below, half depth area, and average cup depth, are acceptably reproducible. CONCLUSION: The TopSS provides three variables which describe the physiological shape of the optic disc that have high reproducibility. These three variables might be useful for following the progression of optic disc changes in glaucoma patients.

Tears of the meniscus as revealed by magnetic resonance imaging.

Forty-four patients who were examined by magnetic resonance imaging and arthroscopy to detect tears of the meniscus of the knee were studied. Twenty-eight patients (Group I) had had no previous operations on the knee. Sixteen patients (Group II) had had a previous operation on the knee that had been performed after a meniscal injury. In Group I, the percentage of correct diagnoses by magnetic resonance imaging was 45 per cent. If the false-negative results are excluded, the rate of accuracy was 65 per cent. Similarly poor results were found in Group II: a rate of accuracy of 49 per cent and, if we eliminate the false-negative results, the rate of accuracy was only 55 per cent.

Pressure-volume relation for the living human eye.

PURPOSE: The pressure-volume relation for an eye is the mathematical equation that relates changes in intraocular pressure to changes in intraocular volume. This relation is useful for calculating outflow facility from tonography and pulsatile ocular blood flow from intraocular pressure pulsations. The present work develops a new relation by culling together all the published direct manometric rigidity measurements on living human eyes. METHODS: A total of 182 data items taken from 21 eyes are available in the 1958-62 literature of Ytteborg, Prijot, Eisenlohr, Langham and Maumenee. The approach was (i) to perform an error analysis based on the various experimental conditions, (ii) to assume general mathematical forms for the relation, (iii) to use least-squares analysis and statistical measures to find the optimal data representation, and (iv) to introduce the total volume of the eye into the formulation. RESULTS: A new formula for the pressure-volume relation for the living human eye is derived relating DeltaV, the change in volume, to P, the corresponding intraocular pressure: DeltaV = V (C + C(0) x ln P + C( 1) x P), where V is the volume of the eye, C, C(0) and C(1) are numerical parameters. This equation gives the most statistically significant fit to the experimental data. CONCLUSION: The new equation for the pressure-volume relation derived from all the currently available ocular rigidity data on the living human eye gives a larger volume increment for a given increment of pressure than Friedenwald's equation based on measurements performed on cadaver eyes.

Arthroscopic Assessment and Treatment of Dancers' Knee Injuries.

In brief: The author saw 16 dancers with a history of dance-related knee injuries that had defied conservative treatment. Arthroscopic examination revealed 15 meniscal tears and four cases of chondromalacia patellae. The meniscal tears were treated by partial arthroscopic meniscectomy and the chondromalacia patellae by shaving, drilling, and debridement of the patella. After surgery the results were rated by means of a physical examination and a patient questionnaire. The results were generally excellent, with 13 of the 16 dancers returning to a preoperative level of dance activity. However, the author stresses the importance of preventing injury by using correct dance technique, wearing knee pads during practice, and avoiding excessively hard floor surfaces.

Arthroscopically-assisted semitendinosus and gracilis tendon graft for anterior and posterior cruciate ligament deficiency.

A simple, reliable, arthroscopically-assisted procedure is presented in which a doubled and suture woven semitendinosus and gracilis free tendon graft is used in the anterior or posterior cruciate ligament deficient knee. A ligament guide system is used for isocentric placement of tibial and femoral drill holes. The procedure is performed using a button and staple technique that allows accurate placement of the ligament substitution and facilitates early ambulation. At an average follow-up of 2.5 years, good and excellent results have been demonstrated in 97% of 74 knees in which this technique was used, with only a 3% risk of graft failure.

Identification of an antigen shared by mouse liver and lung.

In response to multiple injections of liver extract from Balb/c mice, DBA/1 mice produce antibodies against a component of the liver preparation which is not F-antigen, but which is able to precipitate in gel diffusion tests. This antigen is also found in extracts of Balb/c lung, but not in a variety of other organs tested. Liver extracts from all of the inbred strains studied contain the antigen, except extracts from DBA/1 mice. Furthermore, this antigen was not found in the liver or lungs of other vertebrates tested. The antigen has been designated antigen-L1.