A comparison of the insulinotropic and the insulin-inhibitory actions of gut peptides on newborn and adult rat islet cells

The objective of this study was to examine the release of insulin from cultured islet cells, taken from the pancreas of newborn and adult rats, in response to gastric inhibitory polypeptide (GIP), cholecystokinin-8 (CCK-8), calcitonin gene-related peptide (CGRP), and pancreastatin. GIP (10(-9)-10(-7) M) potentiated glucose-stimulated release of insulin in a dose-dependent fashion from both newborn and adult islet cells. CCK-8 (greater than 10(-8) M) also increased glucose-stimulated release of insulin from newborn islet cells, however its effect was not significant and not as strong as that observed with adult islet cells. Culture of newborn islet cells for 3 weeks with media containing high concentrations of glucose (16.7 mM) enhanced insulin release in response to CCK-8. CGRP did not affect the release of insulin from newborn islet cells, whereas at 10(-10) M, it reduced the release of insulin from adult islet cells by 66 +/- 4%. Pancreastatin (10(-9)-10(-8) M) did not affect the release of insulin from newborn islet cells when cells were incubated with 4.2 mM glucose, whereas it stimulated the release of insulin from adult islet cells in a dose-dependent fashion. When incubated with 16.7 mM glucose, pancreastatin inhibited the release of insulin from both newborn and adult islet cells. These results indicate that newborn islet cells experience developmental changes which render them responsive to enteric peptides.     

Short-term synaptic plasticity, simulation of nerve terminal dynamics, and the effects of protein kinase C activation in rat hippocampus

Phorbol esters are hypothesised to produce a protein kinase C (PKC)-dependent increase in the probability of transmitter release via two mechanisms: facilitation of vesicle fusion or increases in synaptic vesicle number and replenishment. We used a combination of electrophysiology and computer simulation to distinguish these possibilities. We constructed a stochastic model of the presynaptic contacts between a pair of hippocampal pyramidal cells that used biologically realistic processes and was constrained by electrophysiological data. The model reproduced faithfully several forms of short-term synaptic plasticity, including short-term synaptic depression (STD), and allowed us to manipulate several experimentally inaccessible processes. Simulation of an increase in the size of the readily releasable vesicle pool and the time of vesicle replenishment decreased STD, whereas simulation of a facilitation of vesicle fusion downstream of Ca²⁺ influx enhanced STD. Because activation of protein kinase C with phorbol ester enhanced STD of EPSCs in rat hippocampal slice cultures, we conclude that an increase in the sensitivity of the release process for Ca²⁺ underlies the potentiation of neurotransmitter release by PKC.     

Organizational and market factors associated with Medicare dependence in inpatient rehabilitation hospitals.

Rehabilitation hospitals in the USA have been excluded from the Medicare Prospective Payment System (PPS) system since 1982, and have received cost-based reimbursement. However, the 1997 Balanced Budget Act mandated a PPS for inpatient rehabilitation, to be implemented by the end of 2002. This study assesses rehabilitation hospitals' dependency on Medicare. Findings show that not-for-profit hospitals, facilities with fewer services, facilities with lower staffing levels, and hospitals with lower operating expenses and profits, have a higher proportion of their inpatient revenue coming from Medicare. These facilities may be vulnerable to the new PPS payment system.     

一项对原发进行性多发性硬化症患者认知功能的纵向研究

有关多发性硬化症患者认知功能的纵向研究很少，并且上述研究的结果也不明确，迄今尚无专门关于原发进行性多发性硬化症（PPMS）病例系列的连续神经心理学资料。横断面分析揭示，PPMS患者的认知功能与磁共振成像（MRI）参数之间显著相关。本研究持续2年时间对来源于5个欧洲中心的99例PPMS患者的认知功能和MRI改变进行探讨。采用简易可重复问卷（一种推理能力测试）和抑郁量表每隔12个月对患者进行评估，同时在每个时间点对T1低信号负荷、T2损伤负荷和部分脑体积的MRI参数进行测算。基线和2年时患者的平均认知功能得分间无显著差异。然而，1／3患者的单独测试得分表现出绝对的认知功能下降。研究结果提示，纳入研究时的初始认知状态是2年后认知能力的一个可靠预测指标。认知功能改变和MRI改变间仅有少数几项指标显著相关，值得一提的是T1低信号负荷与2项注意力测试任务相关（r=-0．266，P=0．017；r=-0．303，P=0．012），可能是由多种因素造成认知功能和MRI参数间的这种弱相关。     

A biometrical genetic approach to chromosome analysis inDrosophila: Detection of epistatic interactions in geotaxis

Chromosome analysis has been widely used as a first step in eclucidating the genetic architecture of several behaviors ofDrosophila melanogaster. These chromosome studies have generally used incomplete designs or fairly simple statistical analyses. Here I reanalyze two data sets on geotaxis from Pyle (1978) and Ksander (1966) using a biometrical genetic design. Results from the biometrical genetic reanalysis suggest that individual differences in geotaxis might be due to genes on all three major chromosomes which show extensive epistatic interactions.     

Inward rectification in response to FMRFamide in Aplysia neuron L2: summation with transient K current

The response of Aplysia abdominal ganglion neuron L2 to the molluscan neuroactive peptide Phe-Met-Arg-Phe-NH2 (FMRFamide) was studied in voltage-clamp experiments. In all of the experiments, focal application of the peptide to the soma activated an inward rectifier current and reduced the apparent amplitude of the transient K current, IA. In a few cells, Na and K currents were activated in addition to these effects. Voltage-jump experiments were performed to study the ionic dependence, kinetics, and voltage dependence of the inward rectifier. Inward rectification increased exponentially during hyperpolarizing pulses and recovered exponentially on return to the resting potential. The reversal potential was variable, but was near -40 mV at the beginning of experiments. Inward rectification was insensitive to changes in external Na, Ca, or K concentration, but lowering the external Cl concentration had complicated effects on current amplitude. When KCl microelectrodes were used, perfusion with low-Cl external saline increased the amplitude of the peptide-dependent inward rectifier and shifted its reversal potential to a more positive voltage. With KAc microelectrodes, perfusion with low-Cl saline reduced the amplitude of the current. Inward rectification increased when a KAc microelectrode was withdrawn and replaced with a low-resistance KCl electrode, even when there was no measurable change in reversal potential. These results suggest that the FMRFamide-dependent inward rectifier is a Cl current that, like the current described by Chesnoy-Marchais (1982, 1983), is modulated by intracellular Cl. FMRFamide reduced the apparent amplitude of IA without affecting the voltage dependence of IA activation or inactivation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dorsal sympathectomy for hyperhidrosis--the posterior paravertebral approach

Definitive therapy for hyperhidrosis is sympathectomy. The authors have used a posterior approach to perform 36 dorsal sympathectomies for upper extremity hyperhidrosis in 18 patients (12 female, 6 male). All 18 patients suffered from excessive sweating of the upper extremity (17 palmar, 1 axillary) that caused significant psychological and occupational problems. Eleven patients (61.1%) had lower extremity involvement as well. For all 18 patients conservative medical treatment had failed. Bilateral operations were performed, via a posterior extrapleural approach, through the bed of the third rib. All 36 limbs were relieved of excess sweating. There were no deaths and only two minor wound complications. In no patient did Horner's syndrome develop. Long-term follow-up did not reveal any recurrence of hyperhidrosis. Two patients did complain of compensatory hyperhidrosis of the lower extremities. Dorsal sympathectomy was effective in all of the patients with upper extremity hyperhidrosis in this series. The posterior approach is technically simple, allows simultaneous bilateral operations, and is associated with only infrequent minor complications.