Influence of contrast on the responses of marmoset lateral geniculate cells to drifting gratings

The responses of lateral geniculate nucleus (LGN) cells in the common marmoset (Callithrix jacchus) to drifting luminance or cone isolating gratings of different spatial frequencies and contrasts were measured. The response noise, defined as the variability of the responses to single sweeps in the complex plane, was independent of stimulus contrast and spatial frequency but increased with increasing overall responsiveness of the cell. The signal-to-noise ratio of parvocellular (PC) cells was smaller than of magnocellular (MC) cells. At each contrast, the response amplitude as a function of spatial frequency could be described with a difference of Gaussians model. With this model, the sizes and the peak sensitivities of the receptive field centers and surrounds were estimated. It was found that receptive field center and surround sizes of LGN cells decrease slightly with increasing contrast. Further, the peak sensitivity decreases with increasing contrast. The two factors are involved in a decrease in responsivity (the response per unit contrast) with increasing contrast which is compatible to response saturation for low spatial frequency stimuli. PC cells did not saturate as much to luminance stimuli although some saturation was found with cone isolating gratings. We found that the response phase lag of both PC and MC cells decreased with increasing contrast, which cannot be explained on the basis of linear response behavior. Apparently the phase of LGN cell responses to drifting gratings is altered in comparison with the retinal inputs by additional nonlinearities.     

人Fas配体蛋白在大肠杆菌中的融合表达与应用

目的：在大肠杆菌中融合表达人Fas配体蛋白。方法：应用RT-PCR技术，从激活的人外周血淋巴细胞中提取总RNA，扩增Fas配体cDNA，克隆入PCR2.1载体，测序验证后，克隆入带有组氨酸盒的表达载体pQE-31，在大肠杆菌中表达，经亲和层析柱纯化后，用SDS-PAGE和Western blot鉴定表达产物。结果：表达的融合蛋白为人Fas配体，其相对分子质量（Mr)为40000。；经透析复性后，具有诱导Jurkat细胞凋亡的作用，用该蛋白分子免疫BALB/c小鼠制备抗血清，以间接ELISA检测了部分自身免疫病与肿瘤患者血清中可溶性的F 苛的含量。结果与进口试剂盒的灵敏性相似。结论：获得FasL单克隆抗体，深入研究FasL的应用提供了材料。     

Oncology service correspondence: Do we communicate?

The aim of this study is to assess the content of letters sent from a hospital oncology service regarding the initial assessment of new referrals and the requirements of hospital specialists and General Practitioners (GPs) regarding oncology service correspondence. The content of letters regarding the initial consultation of 204 consecutive new oncology patients was analysed. General Practitioners and referring specialists were sent a 13‐point survey to gauge their preferences for the information contained in oncology correspondence pertaining to the initial assessment of an oncology patient. Seventy‐two percent of the patients had a letter written following their initial oncology assessment. The GP received a copy of 81% of the letters (58% of the study sample). The diagnosis was recorded in all our letters, and the proposed treatment plan was addressed in 84% of our letters. Both GPs and specialists required information on examination and investigation findings, diagnosis, treatment options, proposed management plan, and what the patient was told. The GPs required further information on current medication, likely side‐effects of the proposed management, and clarification of when to contact the oncologist. The majority of the respondents were in favour of a structured letter.     

PNEUMOPERITONEUM DUE TO PCI IN A PATIENT WITH A STRANGULATED FEMORAL HERNIA

SUMMARY Although pneumatosis cystoides intestinalis (PCI) is a well-recognised condition, an individual surgeon is unlikely to encounter it often. The collected experience of two surgical units in Glasgow teaching hospitals over a 15-year period consisted of five patients.¹ Surgical and radiological trainees may therefore have little or no exposure to the diagnostic difficulties this condition can cause. We report an illustrative case.     

The spleen in Hodgkin disease: diagnostic value of CT

Findings of CT of the spleen were compared with those of histologic examination in 35 patients who had Hodgkin disease. CT provides a simple way to calculate splenic size. This index is also of value in the assessment of the histologic state of the spleen. An accuracy rate of 91%, specificity of 94%, and a sensitivity of 89% in diagnosing splenic localization of lymphoma was found in this study.     

Gallbladder bile: an experimental study in dogs using MR imaging and proton MR spectroscopy

Magnetic resonance (MR) imaging, proton MR spectroscopy, and biochemical analysis were performed to investigate MR signal intensity (SI) differences between concentrated and dilute gallbladder bile of seven fasting and five sincalide-treated dogs. MR images revealed high SI from bile of fasting dogs and low to medium SI in sincalide-treated dogs when spin-echo (SE) pulse sequences with repetition rates of 0.5 and 2.0 sec were used. Proton MR spectra were similar for fasting and sincalide-treated dogs. In fasting dogs, water content in the bile was slightly lower, and cholesterol, phospholipid, and bile acid concentrations were higher. More than 90% of proton signals in all Fourier transform free induction decay spectra emanated from water molecules, and no lipid proton resonances were detected in Fourier transform SE spectra after tau delays of 7 msec. These results indicate that the differences in SI are caused by alterations in relaxation times of water protons, possibly resulting from the interactions of water protons and macromolecules.     

Uterine MR imaging: effects of hormonal stimulation

Magnetic resonance (MR) imaging characteristics of the uterine corpus were evaluated in 40 women divided into five physiologic categories (nine premenarchal, 13 reproductive age not taking hormones, seven reproductive age taking oral contraceptives, six reproductive age taking gonadotropin releasing hormone analog, and five postmenopausal). Images were generated using a 0.35-T magnet and a double spin-echo technique. On both T1-weighted and T2-weighted images, premenarchal and postmenopausal uteri were small and relatively featureless. Uteri on T2-weighted images in reproductive age women not taking exogenous hormones showed variations in endometrial and myometrial width, signal intensity, and T1 and T2 values during the menstrual cycle. Oral contraceptives and gonadotropin releasing hormone analogs caused endometrial atrophy and alterations in myometrial signal intensity and T1 and T2 values. A detailed gynecologic history is therefore essential in the evaluation of uterine anatomy in patients undergoing pelvic MR imaging.     

Neurological symptoms among dental assistants: a cross-sectional study

Background  

Dental assistants help the dentist in preparing material for filling teeth. Amalgam was the filling material mostly commonly used in Norway before 1980, and declined to about 5% of all fillings in 2005. Amalgam is usually an alloy of silver, copper, tin and mercury. Copper amalgam, giving particularly high exposure to mercury was used in Norway until 1994. Metallic mercury is neurotoxic. Few studies of the health of dental assistants exist, despite their exposure to mercury. There are questions about the existence of possible chronic neurological symptoms today within this working group, due to this exposure. The aim of this study was to compare the occurrence of neurological symptoms among dental assistants likely to be exposed to mercury from work with dental filling material, compared to similar health personnel with no such exposure.