Incidence and risk factors for recurrent Clostridioides difficile infection in pediatric at-risk groups in selected Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) hospitals

OBJECTIVES

Incidence and risk factors for recurrent Clostridioides difficile infection (rCDI) are well established in adults, though data are lacking in pediatrics. We aimed to determine incidence of and risk factors for rCDI in pediatrics.

METHODS

This retrospective cohort study of pediatric patients was conducted at 3 tertiary-care hospitals in Canada with laboratory-confirmed CDI between April 1, 2012, and March 31, 2017. rCDI was defined as an episode of CDI occurring 8 weeks or less from diagnostic test date of the primary episode. We used logistic regression to determine and quantify risk factors significantly associated with rCDI.

RESULTS

In total, 286 patients were included in this study. The incidence proportion for rCDI was 12.9%. Among hospitalized patients, the incidence rate was estimated at 2.6 cases of rCDI per 1,000 hospital days at risk (95% confidence interval [CI], 1.7-3.9). Immunocompromised patients had higher incidence of rCDI (17.5%; P = .03) and higher odds of developing rCDI independently of antibiotic treatment given for the primary episode (odds ratio [OR], 2.31; 95% CI, 1.12-5.09). Treatment with vancomycin monotherapy did not show statistically significant protection from rCDI, independently of immunocompromised status (OR, 0.33; 95% CI, 0.05-1.15]).

CONCLUSIONS

The identification of increased risk of rCDI in immunocompromised pediatric patients warrants further research into alternative therapies, prophylaxis, and prevention strategies to prevent recurrent disease burden within these groups. Treatment of the initial episode with vancomycin did not show statistically significant protection from rCDI.

378. Utility of CMV Quantitative PCR in Tissue Biopsy for the Diagnosis of CMV Gastrointestinal Disease among Solid Organ Transplant Recipients

Background

Cytomegalovirus (CMV) infection is an important cause of morbidity after solid organ transplantation (SOT). Rapid and accurate diagnosis of gastrointestinal (GI) CMV disease is central to the early initiation of appropriate therapy. Currently, the diagnosis mainly relies on histopathology on formalin-fixed GI tissue biopsy. CMV diagnosis by quantitative polymerase chain reaction (qPCR) on tissue biopsy is not routinely performed for the diagnosis of tissue invasive disease, but potentially holds many practical advantages over the gold standard including a rapid turnaround time and providing a quantitative objective result.

Methods

We compared the performance of CMV qPCR on fresh GI biopsy with tissue biopsy histopathology for the diagnosis of GI CMV disease.

Results

A total of 62 SOT patients with GI symptoms underwent endoscopic assessment with GI biopsy analyses for both histopathology and tissue CMV qPCR. Twelve patients (19.4%) had proven CMV disease on histopathology. Among them, all had a positive qPCR on biopsy (median value of log 7.7 and 5.4 x107 copies/mL), and all had a positive serum CMV PCR (median value of log 4.5 and 3.4 x104 copies/mL). Of the 49 remaining patients with negative histopathology, 26 (53%) had CMV qPCR positive tissue biopsy specimens with a median log 4.3 and 2.0 x104 copies/mL. Of these 26 patients with histopathology negative/CMV qPCR positive tissue biopsies, 10 had positive serum CMV qPCR. Twenty-four patients were negative for all three tests: histopathology, CMV qPCR on tissue biopsy, and CMV viremia. ROC analysis for optimal threshold value for CMV qPCR on tissue biopsy for diagnosis of confirmed CMV GI disease is 104 824 copies/mL (sensitivity 100%, specificity 82%, area under ROC 0.91).

Conclusion

Our study shows that tissue biopsy CMV qPCR is highly sensitive (sensitivity of 100%) for the diagnosis of CMV GI disease. As such, tissue CMV qPCR may be a useful adjunctive diagnostic tool for the rapid diagnosis of CMV GI disease.

Disclosures

All Authors: No reported disclosures.

n-type Ge/Si antennas for THz sensing

Ge-on-Si plasmonics holds the promise for compact and low-cost solutions in the manipulation of THz radiation. We discuss here the plasmonic properties of doped Ge bow-tie antennas made with a low-point cost CMOS mainstream technology. These antennas display resonances between 500 and 700 GHz, probed by THz time domain spectroscopy. We show surface functionalization of the antennas with a thin layer of α-lipoic acid that red-shifts the antenna resonances by about 20 GHz. Moreover, we show that antennas protected with a silicon nitride cap layer exhibit a comparable red-shift when covered with the biolayer. This suggests that the electromagnetic fields at the hotspot extend well beyond the cap layer, enabling the possibility to use the antennas with an improved protection of the plasmonic material in conjunction with microfluidics.

Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides

The waveguide losses from a range of surface plasmon and double metal waveguides for Ge/Si_1-xGe_x THz quantum cascade laser gain media are investigated at 4.79 THz (62.6 μm wavelength). Double metal waveguides demonstrate lower losses than surface plasmonic guiding with minimum losses for a 10 μm thick active gain region with silver metal of 21 cm^-1 at 300 K reducing to 14.5 cm^-1 at 10 K. Losses for silicon foundry compatible metals including Al and Cu are also provided for comparison and to provide a guide for gain requirements to enable lasers to be fabricated in commercial silicon foundries. To allow these losses to be calculated for a range of designs, the complex refractive index of a range of nominally undoped Si_1-xGe_x with x = 0.7, 0.8 and 0.9 and doped Ge heterolayers were extracted from Fourier transform infrared spectroscopy measurements between 0.1 and 10 THz and from 300 K down to 10 K. The results demonstrate losses comparable to similar designs of GaAs/AlGaAs quantum cascade laser plasmon waveguides indicating that a gain threshold of 15.1 cm^-1 and 23.8 cm^-1 are required to produce a 4.79 THz Ge/SiGe THz laser at 10 K and 300 K, respectively, for 2 mm long double metal waveguide quantum cascade lasers with facet coatings.

High conductivity of ultrathin nanoribbons of SrRuO3 on SrTiO3 probed by infrared spectroscopy

SrRuO3 (SRO) is a perovskite increasingly used in oxide-based electronics both for its intrinsic metallicity, which remains unaltered in thin films and for the ease of deposition on dielectric perovskites like SrTiO3, (STO) to implement SRO/STO microcapacitors and other devices. In order to test the reliability of SRO/STO also as high-current on-chip conductor, when the SRO dimensions are pushed to the nanoscale, here we have measured the electrodynamic properties of arrays of nanoribbons, fabricated by lithography starting from an ultrathin film of SRO deposited on a STO substrate. The nanoribbons are 6 or 4 nm thick, 400, 200 and 100 nm wide and 5 mm long. The measurements have been performed by infrared spectroscopy, a non-contact weakly perturbing technique which also allows one to separately determine the carrier density and their scattering rate or mobility. Far-infrared reflectivity spectra have been analyzed by Rigorous Coupled-Wave Analysis (RCWA) and by an Effective Medium Theory, obtaining consistent results. With the radiation polarized along the nanoribbons, we obtain a carrier density similar to that of a flat film used as reference, which in turn is similar to that of bulk SRO. Moreover, in the nanoribbons the carrier scattering rate is even smaller than in the unpatterned film by about a factor of 2. This shows that the transport properties of SRO deposited on STO remain at least unaltered down to nanometric dimensions, with interesting perspectives for implementing on-chip nano-interconnects in an oxide-based electronics. When excited in the perpendicular direction, the nanoribbons appear instead virtually transparent to the radiation field, as predicted by RCWA.

Low loss Ge-on-Si waveguides operating in the 8-14 µm atmospheric transmission window

Germanium-on-silicon waveguides were modeled, fabricated and characterized at wavelengths ranging from 7.5 to 11 µm. Measured waveguide losses are below 5 dB/cm for both TE and TM polarization and reach values of ∼ 1 dB/cm for ≥ 10 µm wavelengths for the TE polarization. This work demonstrates experimentally for the first time that Ge-on-Si is a viable waveguide platform for sensing in the molecular fingerprint spectral region. Detailed modeling and analysis is presented to identify the various loss contributions, showing that with practical techniques losses below 1 dB/cm could be achieved across the full measurement range.

Orbital dependent coherence temperature and optical anisotropy of V2O3 quasiparticles

We report on an orbital and temperature dependent study of the onset of coherent quasiparticles in V₂O₃ single crystal. By using polarized infrared spectroscopy we demonstrate that the electronic coherence temperature is strongly orbital dependent, being about 400 K for [Formula: see text] orbitals and 500 K for the [Formula: see text]. This suggests that V₂O₃ low energy electrodynamics can be described in terms of two electron liquids differently renormalized by electronic correlations.

Protein clustering in chemically stressed HeLa cells studied by infrared nanospectroscopy

Photo-Thermal Induced Resonance (PTIR) nanospectroscopy, tuned towards amide-I absorption, was used to study the distribution of proteic material in 34 different HeLa cells, of which 18 were chemically stressed by oxidative stress with Na₃AsO₃. The cell nucleus was found to provide a weaker amide-I signal than the surrounding cytoplasm, while the strongest PTIR signal comes from the perinuclear region. AFM topography shows that the cells exposed to oxidative stress undergo a volume reduction with respect to the control cells, through an accumulation of the proteic material around and above the nucleus. This is confirmed by the PTIR maps of the cytoplasm, where the pixels providing a high amide-I signal were identified with a space resolution of ∼300 × 300 nm. By analyzing their distribution with two different statistical procedures we found that the probability to find protein clusters smaller than 0.6 μm in the cytoplasm of stressed HeLa cells is higher by 35% than in the control cells. These results indicate that it is possible to study proteic clustering within single cells by label-free optical nanospectroscopy.

Mapping the amide I absorption in single bacteria and mammalian cells with resonant infrared nanospectroscopy

Infrared (IR) nanospectroscopy performed in conjunction with atomic force microscopy (AFM) is a novel, label-free spectroscopic technique that meets the increasing request for nano-imaging tools with chemical specificity in the field of life sciences. In the novel resonant version of AFM-IR, a mid-IR wavelength-tunable quantum cascade laser illuminates the sample below an AFM tip working in contact mode, and the repetition rate of the mid-IR pulses matches the cantilever mechanical resonance frequency. The AFM-IR signal is the amplitude of the cantilever oscillations driven by the thermal expansion of the sample after absorption of mid-IR radiation. Using purposely nanofabricated polymer samples, here we demonstrate that the AFM-IR signal increases linearly with the sample thickness t for t > 50 nm, as expected from the thermal expansion model of the sample volume below the AFM tip. We then show the capability of the apparatus to derive information on the protein distribution in single cells through mapping of the AFM-IR signal related to the amide-I mid-IR absorption band at 1660 cm(-1). In Escherichia Coli bacteria we see how the topography changes, observed when the cell hosts a protein over-expression plasmid, are correlated with the amide I signal intensity. In human HeLa cells we obtain evidence that the protein distribution in the cytoplasm and in the nucleus is uneven, with a lateral resolution better than 100 nm.

Pressure-dependent relaxation in the photoexcited mott insulator ET-F2TCNQ: influence of hopping and correlations on quasiparticle recombination rates

We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET-F(2)TCNQ as a function of external pressure, which is used to tune the electronic structure. At each pressure value, we first fit the static optical properties and extract the electronic bandwidth t and the intersite correlation energy V. We then measure the recombination times as a function of pressure, and we correlate them with the corresponding microscopic parameters. We find that the recombination times scale differently than for metals and semiconductors. A fit to our data based on the time-dependent extended Hubbard Hamiltonian suggests that the competition between local recombination and delocalization of the Mott-Hubbard exciton dictates the efficiency of the recombination.

Intrinsic linewidth of the plasmonic resonance in a micrometric metal mesh

The intrinsic linewidth and angular dispersion of Surface Plasmon Polariton resonance of a micrometric metal mesh have been measured with a collimated mid-infrared beam, provided by an External Cavity tunable Quantum Cascade Laser. We show that the use of a collimated beam yields an observed resonance linewidth γ = 12 cm(-1) at the resonance frequency ν0 = 1658 cm(-1), better by an order of magnitude than with a non-collimated beam. The extremely narrow plasmon resonance attained by our mesh is then exploited to reconstruct, by varying the QCL angle of incidence θ, the angular intensity distribution f(θ) of a globar at the focal plane of a conventional imaging setup. We thus show that f(θ) is better reproduced by a Gaussian distribution than by a uniform one, in agreement with ray-tracing simulation.

Polaron physics and crossover transition in magnetite probed by pressure-dependent infrared spectroscopy

The optical properties of magnetite at room temperature were studied by infrared reflectivity measurements as a function of pressure up to 8 GPa. The optical conductivity spectrum consists of a Drude term, two sharp phonon modes, a far-infrared band at around 600 cm(-1) and a pronounced mid-infrared absorption band. With increasing pressure both absorption bands shift to lower frequencies and the phonon modes harden in a linear fashion. Based on the shape of the MIR band, the temperature dependence of the dc transport data, and the occurrence of the far-infrared band in the optical conductivity spectrum, the polaronic coupling strength in magnetite at room temperature should be classified as intermediate. For the lower energy phonon mode an abrupt increase of the linear pressure coefficient occurs at around 6 GPa, which could be attributed to minor alterations of the charge distribution among the different Fe sites.

2,5-diketopiperazines as neuroprotective agents

2,5-diketopiperazines are the simplest cyclic peptides found in nature, commonly biosynthesized from amino acids by different organisms, and represent a promising class of biologically active natural products. Their peculiar heterocyclic structure confers high stability against the proteolysis and constitutes a structural requirement for the active intestinal absorption. Furthermore, the diketopiperazine-based motif is considered as a novel brain shuttle for the delivery of drugs with limited ability to cross the blood-brain barrier (BBB) and can be proposed as an ideal candidate for the rational development of new therapeutic agents. Although these cyclic peptides have been known since the beginning of the 20th century, only recently have they attracted substantial interest with respect to the wide spectrum of their biological properties, including antitumor, antiviral, antifungal, antibacterial and antihyperglycemic activities. In addition to these, the most challenging function of the diketopiperazine derivatives is related with their remarkable neuroprotective and nootropic activity. The aim of the present paper is to provide an overview of the two major classes of diketopiperazines, the TRH-related and the unsaturated derivatives both characterized by a significant ability to protect against neurotoxicity in several experimental models. The neuroprotective profile of these compounds suggests that they may have a future utility in the therapy of neuronal degeneration in vivo, potentially through several different mechanisms.

GPE and GPE analogues as promising neuroprotective agents

The tripeptide glycine-proline-glutamate (GPE) is the naturally cleaved N-terminal tripeptide of insulin-like growth factor-1 (IGF-1) in brain tissues by an acid protease. Although GPE does not bind to IGF-1 receptors and its mode of action is not clear, in vitro studies have demonstrated its ability to stimulate acetylcholine and dopamine release, as well as to protect neurones from diverse induced brain injures. More importantly, GPE has been shown to have potent neuroprotective effects in numerous animal models of hypoxic-ischemic brain injury and neurodegenerative diseases such as Parkinson's, Alzheimer's and Huntington's diseases. As a consequence, GPE was suggested to be a potential target for the rational design of neuroprotective agents. Unfortunately, the use of GPE as a therapeutic agent is limited because of its unfavorable biochemical and pharmacokinetic properties. This review will focus on structural modifications performed on the GPE molecule in order to obtain bioactive analogues with increased pharmacokinetic profile useful for the treatment of central nervous system (CNS) injures and neurodegenerative disorders.

Vibrational spectrum of solid picene (C22H14)

Recently, Mitsuhashi et al observed superconductivity with a transition temperature up to 18 K in potassium doped picene (C(22)H(14)), a polycyclic aromatic hydrocarbon compound (Mitsuhashi et al 2010 Nature 464 76). Theoretical analysis indicates the importance of electron-phonon coupling in the superconducting mechanisms of these systems, with different emphasis on inter- and intra-molecular vibrations, depending on the approximations used. Here we present a combined experimental and ab initio study of the Raman and infrared spectrum of undoped solid picene, which allows us to unambiguously assign the vibrational modes. This combined study enables the identification of the modes which couple strongly to electrons and hence can play an important role in the superconducting properties of the doped samples.

Far infrared properties of the rare-earth scandate DyScO3

We present reflectance measurements in the infrared region on a single crystal the rare-earth scandate DyScO(3). Measurements performed between room temperature and 10 K allow us to determine the frequency of the infrared-active phonons, never investigated experimentally, and to get information on their temperature dependence. A comparison with the phonon peak frequency resulting from ab initio computations is also provided. We finally report detailed data on the frequency dependence of the complex refractive index of DyScO(3) in the terahertz region, which is important in the analysis of terahertz measurements on thin films deposited on DyScO(3).

Removal of endocrine disrupting compounds from wastewater treatment plant effluents by means of advanced oxidation

Municipal sewage and WWTP effluents are considered to be a major source of pollution, regarding the occurrence of endocrine disrupting compounds (EDCs) in the environment. Although removal potential of many EDCs by conventional WWTPs is recognised, literature data are not easily comparable. Besides, in order to reach very low concentrations, a further treatment might be sometimes required. Positive results can be achieved by tertiary chemical oxidation; nevertheless, technical-economic suitability is still to be fully demonstrated. In this work, two estrogen-like susbstances were considered: nonylphenol (NP) (and its parent compounds) and bisphenol A (BPA). The experimental work was conducted at Verona (Northern Italy) WWTP (370,000 p.e.): after a 15 days sampling campaign, which was carried out in order to calculate mass balance of target compounds, chemical oxidation tests were performed on effluent by means of UV/H(2)O(2) process and ozonation. Technical-economic feasibility of these solutions is discussed.

Magnetic-order-induced crystal symmetry lowering in ACr2O4 ferrimagnetic spinels

We demonstrate that the onset of complex spin orders in ACr2O4 spinels with magnetic and Jahn-Teller active A=Fe and Cu ions lowers the lattice symmetry. This is clearly indicated by the emergence of anisotropic lattice dynamics-i.e., by the pronounced phonon splittings-even when experiments probing static distortions fail. The crystal symmetry in the magnetic phase is reduced from tetragonal to orthorhombic for both compounds. The conical spin ordering in FeCr2O4 is also manifested in the hardening of the phonon frequencies. In contrast, the multiferroic CoCr2O4 with no orbital degrees of freedom shows tiny deviations from cubic structure even in its ground state.

Optical properties across the insulator to metal transitions in vanadium oxide compounds

We review the optical properties of three vanadium oxide compounds V(2)O(3), VO(2) and V(3)O(5), belonging to the so-called Magnéli phase. Their electrodynamics across a metal to insulator transition is investigated as a function of both temperature and pressure. We analyse thoroughly the optical results, with a special emphasis on the infrared spectral weight. This allows us to discuss the nature of the mechanisms driving the phase transitions in the three compounds, pointing out the role of electron-electron and electron-phonon interactions in the various cases.

Far-infrared absorption and the metal-to-insulator transition in hole-doped cuprates

By studying the optical conductivity of Bi(2)Sr(2-x)La(x)CuO(6) and Y(0.97)Ca(0.03)Ba(2)Cu(3)O(6), we show that the metal-to-insulator transition in these hole-doped cuprates is driven by the opening of a small gap at low T in the far infrared. Its width is consistent with the observations of angle-resolved photoemission spectroscopy in other cuprates, along the nodal line of the k space. The gap forms as the Drude term turns into a far-infrared absorption, whose peak frequency can be approximately predicted on the basis of a Mott-like transition. Another band in the midinfrared softens with doping but is less sensitive to the metal-to-insulator transition.

Evidence of a pressure-induced metallization process in monoclinic VO2

Raman and combined infrared transmission and reflectivity measurements were carried out at room temperature (RT) on monoclinic VO2 over the 0-19 GPa and 0-14 GPa pressure ranges. Both lattice dynamics and optical gap show a remarkable stability up to P* approximately 10 GPa whereas subtle modifications of V ion arrangements within the monoclinic lattice, together with the onset of a metallization process via band gap filling, are observed for P >P*. Differently from P=0, where the VO2 metallic phase is found only in conjunction with the rutile structure above 340 K, a new RT metallic phase within a monoclinic structure appears accessible in the high pressure regime.

Pressure dependence of the charge-density-wave gap in rare-earth tritellurides

We investigate the pressure dependence of the optical properties of CeTe3, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the midinfrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice compression removes the perfect nesting condition of the Fermi surface and therefore diminishes the impact of the CDW transition on the electronic properties of RTe3.

Low-energy electrodynamics of superconducting diamond

Heavily boron-doped, diamond films can become superconducting with critical temperatures Tc well above 4 K. Here we first measure the reflectivity of such a film down to 5 cm(-1), by also using coherent synchrotron radiation. We thus determine the optical gap 2Delta, the field penetration depth lambda, the range of action of the Ferrell-Glover-Tinkham sum rule, and the electron-phonon spectral function alpha2F(omega). We conclude that diamond behaves as a dirty BCS superconductor.

Twenty-five novel HLA-B alleles

Twenty-five novel HLA-B alleles are described in this paper: B*0729, B*1309, B*1814, B*1815, B*2724, B*2725, B*3539, B*3926, B*4037, B*4040, B*4042, B*4043, B*4044, B*4204, B*440203, B*4428, B*4429, B*4430, B*4505, B*5308, B*5309, B*5510, B*5511, B*570102, and B*5709. Most of the variants are single nucleotide substitutions. Two involve variants at the Bw4/Bw6 epitope. Two alleles carry substitutions of conserved amino acids.

Seventeen novel HLA-A alleles

This paper describes 17 novel HLA-A alleles: A*0244, A*0251, A*0254, A*0309, A*1111, A*2432, A*2434, A*2504, A*2618, A*2905, A*2906, A*3106, A*3107, A*3207, A*6820, A*7407, and A*7408. Most substitutions are found in other alleles.

Novel HLA-B alleles formed by an inter-locus recombination with HLA-C, HLA-B*0713 and B*6702

This paper describes two novel HLA-B locus alleles. B*0713 appears to have resulted from an interlocus recombinational event which inserted a sequence from an HLA-C allele into B*0702. This event altered a significant portion of the alpha-1 domain alpha helix. B*6702 shares much of its exon 2 sequence with B*0713 but is identical in exon 3 to several HLA-B locus alleles including B*67012.

A comparison among different methods for evaluating the biomass activity in activated sludge systems: preliminary results

In order to improve activated sludge plant operation (achieving higher efficiency and cost savings) beside influent and effluent characteristics and working parameters (e.g. dissolved oxygen, total and volatile suspended solids, pH, recirculation flow rate, etc.), the biomass activity should be monitored, the bacteria being responsible for the pollutant degradation. Since conventional cultivation based methods are inadequate to quantify environmental microorganisms (due to scarce number of cultivable microorganisms and time-consuming procedures) several "non-conventional" techniques were applied in this study, in order to compare the obtainable information and their routine feasibility. Different measurements (VSS concentration, Oxygen Uptake Rate, microbial counts by cultural and biomolecular methods--MPN-PCR, ATP content, dehydrogenase activity, microbial cell viability and enzymatic activity) were carried out on mixed liquor samples, taken from a municipal activated sludge plant (440,000 p. e.). The preliminary results of the research are presented in this paper.

Prediction of the interaction effects Ar+ laser-brain tumours by study of the photoacoustic spectroscopy of cerebral oncotypes

A preliminary definition of light absorption spectra of brain neoplasm represents a correct approach to the laser therapy of cerebral tumours. The goal should be the identification of those oncotypes more sensive to the laser energy, allowing consequently a dosage of the energy proportional to the light absorption coefficient, reducing any side effects. With this purpose the coefficients of light-absorption of 63 different brain tumours have been analyzed and defined by means of photocoustic spectrometry. The study has been focused at wavelength of the Ar+ laser (4,600-6,000 A). The results show a close relationship between histology, degree of vascularization and/or pigmentation and light absorption: the more immature and/or pigmented oncotypes show the highest coefficients of optical absorption. In the laser therapy of these neoplasms it will be sufficient to use low powers and short exposure time.

Evaluation of the Ar+ laser thermal effect in rabbit brain tissue by means of optical absorption coefficients. Photoacoustic measurements

In predicting Ar+ laser-neural tissue interaction a determination of the optical absorption properties of brain parenchyma appears indispensable. In this study a determination of absorption spectra of different areas of rabbit brain at the wavelength of an Ar+ laser beam is made. The areas considered in the study are frontal and occipital gray and white substance, thalamus, basal ganglia, cerebellar cortex and choroid plexus. Specimens of these areas measuring 2 X 3 X 3 mm were obtained from coronal sections 1 cm thick of 20 rabbit brains. The analysis of optical properties was made by means of a photoacoustic spectrometer which appears the only suitable technique for testing the optical absorption properties of biological materials. The absorption coefficient results were similar in magnitude and constant in all the areas examined, measuring approximately 50 cm-1. The prediction of lack of any selective effect for the different areas is confirmed by the sizes of lesions made in cerebral specimens of the same areas of the contralateral hemisphere by means of Ar+ laser: the lesions increase in size in proportion to the increase in output power and exposure time, independently of the areas considered. Also the histological examination of the areas shows the same morphology to be independent of the variations of both output power and exposure time. The only differences were the presence for short exposure time and low output power of a carbonized layer inner to the layer of coagulative necrosis.

[Thermal effects of Nd:YAG and Co2 lasers on biological tissues]

The surgical use of CO2 c.w. laser as a knife and of Nd:YAG laser as photocoagulator is generally explained in terms of the different absorption coefficients of the water contained in high amount in the living tissues at the operating wavelengths of the two sources (alphaCO2 congruent to 10(2) cm(-1), alpha Nd congruent to 1cm(-1)). This approach can be shown to be incorrect once spectrophotometric measurements carried out on a mucous membrane and blood give the values gammaCO2 = 200 cm(-1) and gamma Nd = 10 cm(-1) for the effective absorption coefficient (the effective coefficient is gamma = alpha + beta where beta is the internal light scattering coefficient). It is worth noting that gammaCO2 congruent to alpha CO2 but gammaNd congruent to 10alphaNd. Then we have calculated the temperature distribution on tissues irradiated either by Co2 or by Nd laser. In the Co2 irradiation two energy transfer mechanisms are present: the surface optical absorption and the thermal diffusion in the bulk of the tissue. Under Nd irradiation the optical absorption of internally scattered radiation must also be taken into account. The calculation model is based on the classical heat equation, but assuming a "source" given by the expression S (r,z; t) = alpha [IB (r,z; t)+IS (r,z;t)], where IB and IS are respectively the direct and scattered components of a beam propagating along a z direction perpendicular to the tissue surface. The general expression of the temperature increases deltaT (r,z;t) have been obtained for both laser sources. The calculation show that even a few watts CO2 laser can induce a surface temperature rise of about 60 degrees C with negligible bulk effects, depending only on the thermal conductivity and on the irradiation time (knife effect). On the contrary a 40 w Nd:YAG laser induces a 50 degrees C temperature rise in the whole thickness of the tissue becoming in this way unable to "cut" even though it coagulates a region much larger than the beam dimensions.

[Selective posterior radiculotomy in the treatment of spasticity: immediate and long-term results]

Immediate and late results of a series of 44 patients suffering from spastic syndromes, operated on from January 1973 to December 1976 by selective posterior rootlet section, have been analyzed and reported. The operation consisted of a selective section of the dorsomedial part of the rootlets constituting each posterior root and was performed usually from L1 to S1 bilaterally. Thirty patients improved markedly after the operation and there were no immediate or late complications. The procedure caused no sensory disorders. The indications and contraindications to the operation are discussed.

Chronic paleocerebellar stimulation in dystonia and athetosis. Report of two cases

Two patients suffering from dystonia and athetosis have been treated by means of chronic electrical stimulation of the paleocerebellum and were followed for over two and a half years. One of the patients showed signs of slight improvement, while no improvement at all was observed in the other patient. Some observations and problems are discussed.

Bilateral cervical posterior rhizotomy: effects on dystonia and athetosis, on respiration and other autonomic functions

Bilateral cervical posterior rhizotomy of C1 through C4, C5 or C6 was performed in 16 patients affected by dystonia and athetosis resulting from infantile cerebral palsy. The majority showed decreased muscle spasms and athetoid movements, with some improvements in their posture and voluntary mobility. 5 patients suffered from uneven and irregular breathing associated with lethargy immediately postoperatively, and 4 also showed reduced diaphragmatic activity; all 4 of these patients developed pneumonia, transitory in 3, but fatal to the other. Urinary retention lasting for a maximum of 3 months occurred in 4 of the 5 patients. The authors suggest that the lesion of ascending reticular fibers in the cervical posterior roots could have been responsible for the observations.

[Clinical study of dantrolene sodium in the treatment of spastic and dystonic syndromes]

Dantrolene sodium has been given to 45 patients suffering from dyskinetic syndromes: 33 were suffering from spastic syndromes, either secondary to cerebral lesions at birth, or to other cerebral lesions, or to cord lesions; 9 were affected by infantile dystonic syndromes; 1 by dystonia muscolorum deformans and the last 2 patients were suffering from parkinsonism. The best dosage schedule was individual and ranged from 50 mg to 300 mg a day. In this range, the majority of the spastic patients showed reduction of spasticity, unrelated with the site of pathology: a slight one in 12 patients, a moderate one in 9 and a marked one in 2. On the contrary, slight improvement has been noticed in only two of the patients suffering from dystonic syndromes. In no case side effects has been noticed. In all patients who underwent slight or moderate improvement only, we tried to obtain better results on spasticity by growing the dosage schedules; but we have always noticed side effects, that is weakness or drowsiness and, sometimes, urinary uncontinence. Moreover 2 patients showed evidence of transitory metabolic side effects. Therefore our experience shows that dantrolene sodium is an useful drug into the therapy of spasticity, even if often a slight of moderate improvement only is achieved. Slow increase in dosage schedule, repeated laboratory controls and alternate periods of treatment and suspended treatment should be observed.

[Diagnostic and therapeutic problems in dystonia musculorum deformans]

Taking as starging point three patients who unsuccessfully underwent both medical treatment and different neurosurgical interventions, the Authors discuss the problem of the dystonia musculorum deformans nosographic arrangement and its present therapeutical possibilities. They believe that the dystonia musculorum deformans must be considered, rather than as a syndrome, as a real disease, to be distinguished in particular from the various infantile dystonic syndromes and from spasmodic torticollis. In fact in these last morbid forms, at least from a neurosurgical standpoint, the therapeutical possiblities are not so uncertain as those of the dystonia musculorum deformans.