Myogenic and flow-dependent control mechanisms in the coronary microcirculation

Summary We have recently gained evidence that segmental coronary microvascular diameters, and therefore resistances, are controlled by myogenic and endothelial responses to pressure and flow. Furthermore, intact heart studies are demonstrating that these mechanisms may interact importantly with the metabolic mechanisms primarily governing coronary blood flow. Further studies utilizing measurement of segmental coronary microvascular diameters in isolated microvessels and in the beating heart may elucidate the nature of these interactions. Clinical studies may determine whether reversal of endothelial impairment in the diseased coronary microcirculation contributes to autoregulatory vasodilatation, increases resting myocardial perfusion, and increases the threshold for myocardial ischemia during exercise.     

Drive decay theory of self-stimulation: Refractory periods and axon diameters in hypothalamic reward loci

In seven rats with low-threshold self-stimulation loci the diameter of the lateral hypothalamic myelinated axons were measured by light and electron microscopy (Experiment 1). In addition, the electron microscopic study of the axon diameters was continued in 8 loci after an experiment of confirming earlier demonstration of the 0.5 to 0.6 msec long absolute refractory period of the hypothalamic reward system (Experiment 2). Most axon diameters ranged between 0.6 to 1.3 micra. 96.5 and 98.4 per cent of the examined 3251 axons had diameters less than 2 and 3 micra, respectively. In 5 self-stimulation loci we did not observe any axons ranging between 3 to 6 micra in diameter. Measurements of both the axon diameters and the refractory times in the fornix and anterior commissure (Experiment 3) suggest that the absolute refractory period of 0.8 to 1.1 msec measured by Deutsch [5] can only belong to the axons in the lateral hypothalamic self-stimulation loci, but the other period of 0.5 to 0.6 msec would require myelinated axons of about 5 to 6 micra in diameter. Consequently, the findings support the view that the improvement of excitability occurring after the end of a post-stimulatory delay period of 0.5 to 0.6 msec is due to the onset of synaptic activation instead of recovery from axonal refractory state.     

Tooth dimensions and body size in a Pygmy population

Abstract

Background: The relationship between tooth size and stature has been analysed extensively at the interspecies level but has received less attention at the intraspecies level. The relationship between these two parameters does not seem to be the same among modern human populations.

Aim: The aim of this study is to analyse the relationship between tooth dimensions and body measurements in the Baka Pygmies.

Subjects and methods: Height, weight, and tooth dimensions were obtained for 45 adult Baka females and 17 males from Le Bosquet (Cameroon). Correlations were obtained between the variables and compared to results for other human populations.

Results: The Baka population is distinctive in the small number of significant correlations. Only two buccolingual diameters among Baka females show any significant correlation with height. The lack of significant correlations between tooth dimensions and body dimensions among the Baka means that changes in body size are accompanied by random variations in tooth dimensions.

Conclusion: The absence of correlations may be accounted for by the impact of environmental effects on the somatic growth of the Baka producing a Pygmy phenotype adapted to live in the forest. It is worth noting that many correlations become significant when sexes are pooled.     

Number and distribution of taste buds in the oral cavity of hatchling chicks

The location and number of taste buds were mapped in palatal epithelia of one-day old chicks and bud widths measured. Bud counts additionally were recorded for the tongue, and floor of the lower beak. An average of 316 taste buds was observed in the oral cavity of which 69%, 29% and 2% were distributed across oral epithelium in the upper beak (palate), lower beak and posteroventrolateral region of the anterior tongue, respectively. In each oral region, salivary gland ducts lying adjacent as well as gland ductules penetrating through the buds were prevalent. This relation may provide the bio-fluid milieu for receptor stimulation during feeding. Widths of palatal buds were bimodally distributed, peaking at diameters between 40-49 and 60-69 microns. The taste bud-rich oral epithelium in these one-day old chicks is consonant with their precocial nature. The topographic distribution of taste buds appears to be in register with those regions of epithelium contacted by food which is transported anteroposteriorly through the oral cavity by the chicken's prehensile tongue.     

Brain arterial dilatation and the risk of Alzheimer's disease

IntroductionWe tested the hypothesis that brain arterial dilatation increases the risk of Alzheimer's dementia (AD).MethodsWe studied dementia-free participants in the Washington Heights-Inwood Columbia Aging Project who had a brain MRI and post-MRI dementia adjudication. We measured the axial T2-proton density diameters of the intracranial carotids and basilar diameters and used Cox models to obtain AD hazard ratios and 95% intervals.ResultsOf 953 participants (mean age 77 ± 7 y, women 64%, 71% nonwhite) followed on average for 3 ± 3 years, 76 (8%) developed AD. In a model adjusted for demographics, vascular risks, apolipoprotein E (APOE)-ε4, and white matter hyperintensities, larger carotid diameters increased the risk of AD, defined categorically as ≥ 90th percentile (HR 4.34, 1.70–11.11) or continuously (HR 1.44 per SD, 1.07–1.94).DiscussionUnderstanding the pathophysiology of the association between AD and brain arterial dilatation may reveal new clues to the vascular contributions to AD.     

Pharmaceutical strategies to extend pulmonary exposure of inhaled medicines

Pulmonary administration route has been extensively exploited for the treatment of local lung diseases such as asthma, chronic obstructive pulmonary diseases and respiratory infections, and systemic diseases such as diabetes. Most inhaled medicines could be cleared rapidly from the lungs and their therapeutic effects are transit. The inhaled medicines with extended pulmonary exposure may not only improve the patient compliance by reducing the frequency of drug administration, but also enhance the clinical benefits to the patients with improved therapeutic outcomes. This article systematically reviews the physical and chemical strategies to extend the pulmonary exposure of the inhaled medicines. It starts with an introduction of various physiological and pathophysiological barriers for designing inhaled medicines with extended lung exposure, which is followed by recent advances in various strategies to overcome these barriers. Finally, the applications of the inhaled medicines with extended lung exposure for the treatment of various diseases and the safety concerns associated to various strategies to extend the pulmonary exposure of the inhaled medicines are summarized.     

不同管径TiO2纳米管对小鼠C2C12成肌细胞增殖分化影响的实验研究

目的:研究不同管径TiO₂纳米管对于小鼠C2C12成肌细胞增殖、铺展、黏附和分化的影响。方法:通过阳极氧化的方法,用10、15、20 V电压制备3组不同管径的TiO₂纳米管,扫描电镜(scanning electron microscope,SEM)测得3组管径分别为25、50、100 nm。在各组样品表面接种C2C12成肌细胞,用CCK-8法检测细胞增殖情况,SEM观察细胞形态,实时定量聚合酶链反应(real-time quantitative polymerase chain reaction,RT-qPCR)观察不同管径TiO₂纳米管对于小鼠C2C12成肌细胞分化相关基因表达的影响。结果:不同管径TiO₂纳米管均促进了C2C12成肌细胞的增殖,其中50 nm管径组效果最佳,100 nm管径组效果减弱。50 nm和100 nm管径组能伸展出更多的伪足和伪板,促进了细胞的黏附和铺展。50 nm管径组在3 d和7 d时均上调了Myog、Myh3和Myod1这类成肌相关基因的表达。结论:50 nm管径的TiO₂纳米管能促进小鼠C2C12成肌细胞的增殖、铺展、黏附和分化。     

Standards for ultrasound guidance of suprapubic bladder aspiration

 We performed a prospective study of 40 infants with suspected urinary tract infection to determine standards for ultrasound guidance of suprapubic bladder aspiration (SBA). Only transverse bladder diameter showed a significant correlation with bladder volume (r = 0.83, P<0.001). Urine was obtained in 36 patients (90%). The mean transverse diameter was 4.4 ± 0.8 cm (range 3–6.1 cm). In the 4 patients (10%) in whom urine was not obtained, the transverse diameter was 3.2 ± 0.2 cm (range 2.9–3.5 cm). Our findings indicate that a SBA is more likely to be successful when the transverse diameter is above 3.5 cm, whereas when the diameter is lower than 3 cm the procedure is less likely to be successful. Received September 9, 1996; received in revised form and accepted February 20, 1997