Freeze-etch and histochemical evidence for cycling in crayfish photoreceptor membranes

Freeze-etched rhabdoms and adjacent cytoplasmic cytoplasmic organelles from crayfish compound eyes have been studied for evidence of photoreceptor membrane cycling. The protoplasmic leaflet face (PF) of split photoreceptor membrane of the microvilli is richly particulate. The particles (92 +/- 16 A in diameter in surface fractures; 70 +/- 9 A in cross fractures; density about 8000/mum2) probably indicate rhodopsin molecule localization. Closely similar particles appear in membranes of pinocytotic vesicles, multivesicular bodies (MVB) and secondary lysosomes. In contrast other retinular cell membranes like plasma membrane remote from the rhabdom are quite distinct (60 +/- 23 A particle diameter, density ca 1000/mum2.) Histochemical tests for acid phosphatase demonstrate its presence in well-developed (but not early stage) MVBs, mixed lamellar vesicular bodies (LVB) and lamellar bodies. Density of PF particles decreases from 8000 in MVB to roughly 4500/mum2 in LVB indicating a degradative sequence from rhabdom to lamellar bodies. Membrane leaflet orientations show that primary endocytosis from microvilli must be followed by secondary endocytosis of fused coated vesicles to form MVB. Morphological evidence for photoreceptor membrane resynthesis has not been found yet in crayfish but some has been obtained in other crustaceans.     

The role of expressive writing in ego identity formation.

Conducted 2 studies with 114 college students to assess the relationship between expressive writing and ego identity development. In both studies, poetry writers were more likely than students not writing poetry to be in the identity achievement status. Poetry writers were less frequently found in the foreclosure status (Study 1) and identity diffusion status (Study 2). No differences in identity development were found between students keeping personal journals and those who had not kept journals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the thermal expansion and crystallography of cubic (C) and monoclinic (B) forms of Gd2O3 in the temperature range 20 to 900°C

Thermal expansion coefficients of B-form (monoclinic) and C-form (cubic) Gd₂O₃ have been measured in the temperature range 20 to 900° C, by X-ray diffractometry. The thermal expansion coefficients of both cubic and monoclinic material are linear in the temperature range studied. The expansion of monoclinic material is, however, very anisotropic, and the minor axis of the thermal expansion ellipsoid is not parallel to the edge of the primitive cell to which Gd₂O₃ has been assigned. It is noted that the anisotropy in expansion behaviour of this material indicates that anisotropic growth probably occurs during irradiation.     

Mating tactics of male Cape ground squirrels, Xerus inauris: consequences of year-round breeding

The purpose of this study was to determine the advantage of a three-dimensional (3D) single-shot fast-spin-echo (SSFSE) sequence to obtain MR cholangiopancreatography (MRCP) with a .5-T MR unit by comparison with a two-dimensional (2D) SSFSE sequence. MRCP with 2D-SSFSE and with 3D-SSFSE with 128 echo train lengths was performed on 15 volunteers and 38 patients with pancreatobiliary disease using a .5-T MR unit. For maximum intensity projection (MIP) reconstruction, the section thickness of source images was 4 mm in the 2D-SSFSE and 3 mm in the 3D-SSFSE. 3D volume data in 3D-SSFSE were obtained using repeated short breath-hold of 2 seconds for every repetition time throughout the examination. The image quality, duct conspicuity, signal-intensity ratio (SIR), and contrast-to-noise ratio (CNR) were evaluated. In 23 of the patients who underwent both MRCP and direct cholangiopancreatography (endoscopic retrograde cholangiopancreatography [ERCP]/percutaneous transhepatic cholangiography [PTC]), a comparison between these two modalities was also conducted. The image quality of the MIP image with 3D-SSFSE (49 of 53, 92.5% graded excellent or good) was superior to that with 2D-SSFSE (31 of 53, 58.4%). Duct conspicuity, SIR, and CNR were significantly higher with 3D-SSFSE than with 2D-SSFSE. 3D-SSFSE also showed a stronger relationship with the ERCP/PTC findings compared to 2D-SSFSE. 3D-SSFSE provided satisfactory quality, SIR, and CNR of MRCP images, even when a .5-T MR unit was used, because the breath-hold technique used during 3D data sampling minimized all types of motion effects.     

Transthoracic Doppler echocardiography of normally originating coronary arteries in children

Transthoracic Doppler color flow and spectral velocity patterns of normal coronary arteries in children have not been well studied. We designed this study to evaluate coronary artery flow velocity characteristics in normal and hypertrophied hearts. Sixty-eight children with optimal two-dimensional echocardiographic images of the left coronary artery (LCA) and right coronary artery (RCA) were prospectively studied. The heart was normal in 45 children, and 23 had left and/or right ventricular hypertrophy assessed by echocardiography (mean age 5.8 versus 5.2 years, p = NS). Color flow signals were detected in the LCA in 63(92%) of the 68 children studied, and pulsed Doppler spectral waveforms were recorded in 47 (69%). The latter were recorded in 26 (58%) of 45 normal children and in 21 (91%) of 23 children with left ventricular hypertrophy. Diastolic RCA flow signals were detected mostly in those with right ventricular hypertrophy (10 of 10). Higher levels of LCA maximum diastolic velocity (42 +/- 23 versus 24 +/- 6 cm/sec, p = 0.0004), increased diastolic flow (16 +/- 15 versus 6 +/- 4 ml/min, p = 0.01), and delayed time to peak diastolic velocity expressed as a percentage of diastolic spectral duration (38% +/- 14% versus 20% +/- 8%, p = 0.0001) were observed in children with left ventricular hypertrophy than in those in normal children. A strong correlation was present between Doppler-derived LCA flow and left ventricular mass/m2 (r = 0.7, p = 0.001). In normal hearts, LCA spectral velocity pattern did not change with increasing age, but the time velocity integral became progressively larger, resulting in a strong correlation with weight (p < 0.001, r = 0.78). This study demonstrates (1) LCA flow signals can be detected and quantitated in the majority of children with and those without left ventricular hypertrophy. (2) Left ventricular hypertrophy is associated with increased LCA flow, higher diastolic velocity, and delayed peak diastolic velocity. (3) RCA flow signals are mostly detected when there is right ventricular hypertrophy. Studies on larger groups of patients are needed to further confirm our observations and to enhance understanding of coronary artery flow reserve.     

Plastics in automobiles at SITEV '81

In the March 1981 edition of Materials in Engineering (P149) D. Charlesworth ‘Potential use for plastics in Automobiles’, reviewed in terms of materials properties and processing methods the advantages and limitations of plastics in comparison with metals. In order to convince car makers of the potential of plastics, materials suppliers and component manufacturers develop prototype parts which are publicly displayed, often for the first time, at motor shows. The most important of these shows is the International Exhibition of Suppliers to the Vehicle Industry (SITEV). SITEV '81 took place in Geneva and the more significant new applications of plastics to automobile components are reviewed and their likelihood of adaption by the automotive industry assessed in this article by Dr. N.A. Waterman who is a consultant on materials selection to the plastics and automotive industries.     

The response of human tumour blood flow to a fractionated course of thermoradiotherapy

The response of human tumour blood flow to a fractionated course of thermoradiotherapy was documented in four superficial but bulky tumours (three adenocarcinomas, one melanoma). Blood flow was measured 15, 30, 45, and 60 min after the onset of heating. These measurements were made at the same intra-tumour point during each heat fraction by use of a modified thermal clearance technique in which a correction was made for the heat dissipated by thermal conduction. This point was at least 2 cm beneath the surface in the central portion of the tumour. Extracellular pH was measured within 1 cm of this point prior to the first heat fraction and 2-3 weeks later. Hyperthermia was administered for 60 min, twice a week for 4 weeks by use of a 16-channel 915 MHz microwave applicator. Each patient also received a radiation dose of 40 Gy fractionated at 2 Gy/fx, five times a week (adenocarcinomas) or 4 Gy/fx, twice a week (melanoma). Blood flow remained relatively constant during heating after steady state conditions were attained. However, an overall decrease in tumour blood flow was observed in each patient over the course of thermoradiotherapy. In each case, a relatively small decrease in blood flow occurred between most heat fractions which resulted in an overall decrease which ranged from 50-100%. However, there was a tendency for blood flow to increase following the initial heat fraction at points where the steady state temperature was approximately 41 degrees C or less. Extracellular pH increased in two of three patients and decreased in the other.