The growth of the second underpotentially deposited silver layer on Pt(100)

The electrodeposition of Ag on Pt(100)-(1 × 1) in perchlorate electrolyte was studied by means of time-resolved in situ scanning tunnelling microscopy (STM) and cyclic voltammetry. One monolayer of Ag is deposited underpotentially (upd) ca. 500 mV positive of the Ag⁺/Ag equilibrium potential. Several millivolts positive of the equilibrium potential, a second well defined upd layer forms. Its growth was observed to proceed via island formation and coalescence. This process occurs in two separate stages that manifest themselves in voltammetric peaks as well as in the STM images.     

Characterization of apoptosis in intestinal ischaemia-reperfusion injury — a light and electron microscopic study.

Intestinal ischaemia-reperfusion (IR) injury has largely been attributed to cellular necrosis. Apoptosis, a distinct form of cell death has been observed following IR to the brain, heart, adrenals and the kidneys. In order to characterize the role of apoptosis in intestinal IR, small bowel grafts were stored in saline ( n  = 6) or modified University of Wisconsin solution ( n  = 6) at 4 °C for 12 h and reperfused for 6 h in syngeneic rats. Samples of normal, stored and reperfused intestines at 1, 3 and 6 h were analysed by light and electron microscopy. Following reperfusion, there was crypt and villous epithelial apoptosis, loss of crypt and villous structures, and an increase in mucosal inflammatory cell infiltration. Ongoing apoptosis was maximum at 1 h, its degree decreasing with increasing reperfusion intervals. Large numbers of apoptotic bodies dominated the picture from 3 h of reperfusion. This study has demonstrated the induction of apoptosis by intestinal IR injury, which begins within an hour of reperfusion and is probably responsible for the observed crypt and villous loss. This has potential therapeutic implications as, opposed to necrosis, apoptosis is an active process with genetic regulators and biochemical effectors, which can be specifically targeted to prevent or alleviate IR injury.     

GABAergic and glycinergic inputs to the rabbit oculomotor nucleus with special emphasis on the medial rectus subdivision

Contradictory results have been reported about the inhibitory input to the medial rectus subdivision of the oculomotor nucleus of the cat. In the present ultrastructural study, we quantified the GABAergic and glycinergic terminals in the various subdivisions of the rabbit oculomotor nucleus with the use of post-embedding immunocytochemistry combined with retrograde tracing of horseradish peroxidase. The density of the GABAergic input to the medial rectus subdivision was as substantial as that to the other subdivisions and the postsynaptic distribution of the GABAergic and glycinergic innervation did not differ among the different oculomotor subdivisions.     

Respiratory muscle rigidity in a preterm infant after use of fentanyl during Caesarean section

Fentanyl is in many neonatal intensive care units the sedative of choice. One side-effect is, however, the possibility of muscle and/or chest wall rigidity. A pregnant woman with a critical pulmonary valve stenosis had a balloon dilatation at 26 weeks of gestation. She was put on propranolol, but went into a severe cardiac failure. In week 31, she developed pregnancy induced hypertension. Periodically absent diastolic flow in the umbilical cord was demonstrated. A Caesarean section was performed using fentanyl as analgesia. A boy weighing 1440 g, had a 1 min Apgar score of 3 without respiratory movements. Mask ventilation was tried, but chest wall expansion was not achieved despite using high pressures. He was intubated and positive pressure ventilation attempted, with the same result. Despite the use of high pressures up to 60–70 cm H₂O, no chest movement could be achieved. An intravenous line was established in order to give naloxone and pancuronium. Just before the drugs were given, chest wall movements were achieved and the heart rate normalized. Conclusion This is the first report on chest wall rigidity in a neonate after administration of fentanyl to the mother during Caesarean section. Received: 15 August 1997 and in revised form 30 January 1998 / Accepted 3 February 1998     

Duchenne型肌营养不良症105例临床分析及其发病机制的探讨（附4例肌纤维膜冷冻断裂电镜检查）

报告１０５例Ｄｕｃｈｅｎｎｅ型肌营养不良症（ＤＭＤ），其中男１０３例，女２例。年龄４～１９岁，平均６５岁。３２例有阳性家族史。文中对ＤＭＤ的临床表现，血清酶、肌肉病理、组织化学、电镜检查等特点进行了讨论。对其中４例骨骼肌进行肌纤维膜冷冻断裂电镜检查。结果表明，本病肌膜的Ｅ面和Ｐ面的膜蛋白颗粒密度降低，与２例正常骨骼肌相比有显著性差异，支持本病发病机理中的“膜缺陷”学说。     

Peritoneal morphology in children treated by continuous ambulatory peritoneal dialysis

Fifty peritoneal biopsies (PB) from 35 patients with end-stage renal disease, treated by continuous ambulatory peritoneal dialysis (CAPD) and aged 2 months to 18 years, were examined by light microscopy (n=50) and/or scanning electron microscopy. PB were performed during surgical procedures immediately before the start of, during, or after the cessation of CAPD treatment. PB from 15 children without renal disease undergoing laparatomy were examined similarly. Before the start of CAPD, a scarcity and shortening of the mesothelial microvilli was observed by scanning electron microscopy. During and after CAPD, variable alterations of mesothelium, interstitium and capillaries were found. The mesothelial layer was absent in all 5 PB obtained during episodes of active peritonitis. In patients treated by CAPD for longer than 6 months, mesothelial denudation was observed more frequently (6/11) than in children treated for shorter periods (1/7) (P<0.08). Fibrosis of the peritoneal membrane was present in about 50% of patients during or after the cessation of CAPD without impairment of peritoneal function. No correlation was found between the presence of fibrosis and the frequency of peritonitis or the duration of CAPD treatment.     

人乳头瘤病毒感染超微结构观察

本文对5例典型尖锐湿疣标本及10例可疑人乳头瘤病毒感染标本进行透射电子显微镜观察。结果典型尖锐湿疣标本中仅1例于细胞核内见到人乳头瘤病毒,排列规则呈结晶状。其余14例标本的细胞内均见不同程度的由病毒感染所引起的非特异性病理变化。本文对人孔头瘤病毒及受感染细胞的超微结构进行了初步探讨。     

Ultrastructural distribution of NADPH-diaphorase in the normal hippocampus and after long-term potentiation

Summary The distribution of the enzyme nitric oxide synthase (NOS) was investigated at the ultrastructural level in synaptic structures of the hippocampal formation in relation to long-term potentiation (LTP), based on the histochemical NADPH-diaphorase (NADPH-d) staining with the tetrazolium salt BSPT. BSPT-formazan, the osmiophilic reaction product, was found to be selectively distributed and predominantly attached to membranes of the endoplasmic reticulum. In synaptic regions mainly the presynaptic sides showed labeling. Although several groups have demonstrated a principal involvement of NO in the LTP-mechanism, we found only a low, statistically insignificant increase in NADPH-d stained presynaptic areas of the dentate gyrus, where LTP was evoked. Postsynaptic elements also did not show any noticeable differences. Based on the present results, the predominantly presynaptic localization of NOS should be preferably considered in models describing a functional role of NO in LTP formation, despite the fact that we failed to reveal any indications for an LTP-related change in synaptically located NADPH-d.     

ONCOCYTES OF THE THYROID: A NEUTRAL RED DYE UPTAKE STUDY

Oncocytosis and oncocytomas have attracted attention because on the one hand there have been reports of the favourable prognosis and generally benign nature of oncocytic tumours, while on the other hand, Hurthle cell change in thyroid neoplasms have been reported to be correlated with aggressive biological behaviour and a significantly worse clinical course. Presently, there appear to be two schools of thought on the significance of oncocytosis: (i) a process where there is redifferentiation of cells with involvement in the pathogenesis of cancer; and (ii) a compensatory process for ‘functional exhaustion’ of the cell. Many aspects of oncocytosis seem unclear. In this study, transmission electron microscopy is used to demonstrate the presence of thyroid oncocytes in the hemithyroidectomy specimen of a patient with focal lymphocytic thyroiditis. Tissue sections from this specimen did not display preferential uptake of neutral red dye, a distinctive characteristic of M-phase cancer cells which was previously reported. The findings seem to suggest that oncocytes are not cells with distinctive proliferative potentials. If that were the case, then oncogenesis or cancer cell progression and oncocytosis may not be convergent processes.