Transport in regional science: The “death of distance” is premature

Transport costs have always been an important dimension in regional science. It is therefore remarkable that regional science and transport economics have developed in a rather unconnected way. Although being distinct, the routes of the two were parallel, and there are signs that the two fields will get closer to each other. This paper further discusses long run trends in transport costs and the potential spatial consequences. The main conclusion is that although in terms of money and time, the performance of transport has improved enormously, many economic activities have not become footloose to the extent as expressed by the notion of death of distance. One of the reasons discussed is the role of transaction costs, some being clearly related with distance.JEL Classification: R0, R4The authors thank the guest-editors and an anonymous referee for helpful comments.     

Job mobility, residential mobility and commuting: A theoretical analysis using search theory

The decision to move job and the decision to move residence are closely related dynamic discrete choices, as both moves involve a change of commuting distance. This suggests that labour and residential mobility are mutually dependent and should be simultaneously analysed, based on a theory which incorporates these dynamic decisions explicitly. In the present paper, we base our analysis on search theory and choose the point of departure that individuals maximise utility by moving through different labour market and housing market states, while taking into consideration that moving from one state to another is costly. Based on these assumptions, a search model is constructed and the optimality conditions are derived.  One of main conclusions based on the search model is that the effect of factors which cause housing market imperfections (viz. the residential moving costs and the residence arrival rate) have ambiguous effects on he job acceptance and job search behaviour of employed individuals. For some interesting cases however, the effect of the residential moving costs on the job acceptance behaviour can be derived. In contrast, the effect of housing market imperfections on the labour market behaviour of nonemployed persons is determined. We find for example that housing policies which discourage nonemployed persons to move residence (e.g. housing subsidies) also decrease the probability of becoming employed and may therefore unintentionally increase the number of nonemployed persons. Received: December 1997/Accepted: March 1999     

Benefits and costs of transport

Abstract. This article aims to bring together insights from a broad body of recent literature concerned with the nature, the measurement and policy implications of benefits and costs of transport. It is argued that, for various reasons, transport cannot be treated as an'ordinary'economic sector, and the policy implications of a number of the sector's peculiarities are addressed. Explicit attention is given to spatial aspects and network elements, internal and external benefits and costs, and efficiency aspects and equity considerations in policy making.     

Prevalence of malaria in Dakar, Senegal. Comparative study of the plasmodial indices in pregnant and non-pregnant women

One hundred ASA I orthopaedic surgical patients (four randomized groups) were anaesthetized using continuous propofol and intermittent fentanyl (TIVA), with controlled ventilation via a tracheal tube in groups 1 and 2, and a laryngeal mask airway (LMA) in groups 3 and 4. Neuromuscular blockers were used in groups 1 and 3 only. There were no significant differences between groups in total anaesthetic requirements, as assessed by cardiovascular variables and movement. Coughing interfered with surgery and made controlled ventilation difficult to manage. In contrast, movement not associated with coughing did not impair surgery or ventilation. Patients in group 2 (tracheal tube, no neuromuscular blocker) required more interventions for coughing than the other groups, while patients in group 4 (LMA, no neuromuscular blocker) needed more boluses for movement than groups 1 and 3. Groups 1 and 2 (tracheal tube) had significantly higher heart rates and mean arterial pressures than groups 3 and 4 for varying periods up to 5 min after insertion of the airway management device. There was no correlation between mean arterial pressure and plasma concentrations of catecholamines related to insertion of either the tracheal tube or LMA. The LMA was found to be a highly effective device for controlled ventilation in TIVA and easier to manage than the tracheal tube in the absence of neuromuscular blockers.     

The choice of the method for the surgical treatment of bladder exstrophy

129 children with exstrophy of the bladder underwent primary surgical reconstruction according to G. A. Bairov. Morphofunctional findings in these children gave grounds for determination of three degrees of the bladder congenital defects. 39 patients had defect of the 1st degree, 53 of the 2nd and 37 of the 3d degree. The results of plastic reconstruction of the bladder with local tissue support the validity of such procedure only for patients with the congenital defect degree I. For degree II the benefit is relative. In degree III plastic surgery in contraindicated.     

Uncoupling of stem cell inhibition from monocyte chemoattraction in MIP-1alpha by mutagenesis of the proteoglycan binding site

We have studied the role of proteoglycans in the function of Macrophage Inflammatory Protein-1 alpha (MIP-1alpha), a member of the proteoglycan binding chemokine family. Sequence and peptide analysis has identified a basic region within MIP-1alpha which appears to be the major determinant of proteoglycan binding and we have now produced a mutant of MIP-1alpha lacking the basic charges on two of the amino acids within this proteoglycan binding site. This mutant (Hep Mut) appears to have lost the ability to bind to proteoglycans. Bioassay of Hep Mut indicates that it has retained stem cell inhibitory properties but has a compromised activity as a monocyte chemoattractant, thus suggesting uncoupling of these two properties of MIP-1alpha. Receptor studies have indicated that the inactivity of Hep Mut on human monocytes correlates with its inability to bind to CCR1, a cloned human MIP-1alpha receptor. In addition, studies using proteoglycan deficient cells transfected with CCR1 have indicated that the proteoglycan binding site in MIP-1alpha is a site that is also involved in the docking of MIP-1alpha to the monocyte receptor. The site for interaction with the stem cell receptor must therefore be distinct, suggesting that MIP-1alpha utilizes different receptors for these two different biological processes.     

Tyrosine phosphorylation of the Kv1.3 potassium channel

Kv1.3, a voltage-dependent potassium channel cloned from mammalian brain and T lymphocytes, contains multiple tyrosine residues that are putative targets for tyrosine kinases. We have examined the tyrosine phosphorylation of Kv1.3, expressed transiently in human embryonic kidney (or HEK) 293 cells, by endogenous and coexpressed tyrosine kinases. Tyrosine phosphorylation is measured by a strategy of immunoprecipitation followed by. Western blot analysis, using antibodies that specifically recognize Kv1.3 and phosphotyrosine. Coexpression of the constitutively active tyrosine kinase v-src, together with Kv1.3, causes a large increase in the tyrosine phosphorylation of the channel protein. This phosphorylation of Kv1.3 can be reversed by treatment with alkaline phosphatase before Western blot analysis. Coexpression with a receptor tyrosine kinase, the human epidermal growth factor receptor, also causes an increase in tyrosine phosphorylation of Kv1.3. The effects of endogenous tyrosine kinases were examined by treating Kv1.3-transfected cells with the specific membrane-permeant tyrosine phosphatase inhibitor pervanadate. Pervanadate treatment causes a time- and concentration-dependent increase in the tyrosine phosphorylation of Kv1.3. This increased tyrosine phosphorylation of Kv1.3 is accompanied by a time-dependent decrease in Kv1.3 current, measured by patch-clamp analysis with cell-attached membrane patches. The pervanadate-induced suppression of current and much of the channel tyrosine phosphorylation are eliminated by mutation of a specific tyrosine residue, at position 449 of Kv1.3, to phenylalanine. Thus, there is a continual phosphorylation and dephosphorylation of Kv1.3 by endogenous kinases and phosphatases, and perturbation of this constitutive phosphorylation/dephosphorylation cycle can profoundly influence channel activity.     

Correlation between pharmacokinetic parameters of rifampicin and its biologically active metabolite as related to estimation of the relative bioavailability of the antibiotic

In the bioavailability studies with drugs biotransformed to biologically active metabolities only the concentrations of the parent drug (PD) are usually taken into account even when the pharmacokinetic data on the metabolite(s) (M) are available. However, such data may be useful as an alternative source for the bioavailability determination. Moreover, the clinical outcomes often depend on both the PD and M concentrations. The aim of the study performed with two rifampicin formulations, tablets and dragee, was to correlate the pharmacokinetic parameters of the PD and 25-O-deacetylrifampicin, a microbiologically active M of rifampicin, and to examine whether the bioavailability parameters based on the PD and M concentrations were compatible. The serum concentrations of the PD and M were determined in 8 healthy volunteers by HPLC. Despite different patterns of the PD and M pharmacokinetic profiles the PD peak concentration (Cmax) and especially the AUC correlated with Cmax or the AUC of the M (r = 0.76 and 0.92 respectively). Moreover, the extent of the absorption expressed as the AUC ratio for the PD correlated with the AUC ratio for the M (r = 0.86). However, neither the time to reach the maximum (tmax), nor the Cmax/AUC ratio, a measure of the absorption rate, based on the PD pharmacokinetic data correlated with the respective parameters calculated with using the M concentrations. Thus, only the estimates of the extent of the absorption and not of the absorption rate based on the PD and M data may be considered as compatible.     

Efficacy of silicone punctal plugs as adjuncts to topical pharmacotherapy of glaucoma--a pilot study. Punctal Plugs in Glaucoma Study Group

BACKGROUND: The concept of enhancing the ocular hypotensive effects of topical antiglaucoma medications by impeding lacrimal drainage of medication has been insufficiently studied. This investigation sought to evaluate the effect of bilateral inferior punctal occlusion using silicone punctal plugs on the ocular hypotensive effect of topically applied timolol. METHODS: A randomized, double-masked, cross-over clinical trial was conducted, comparing the ocular hypotensive effect of timolol maleate 0.25 percent, both with and without occlusion of the inferior punctum with the Freeman silicone punctal plug. Following a 2-week washout of topical medication, 17 subjects with early primary open-angle glaucoma or ocular hypertension received one drop of timolol 0.25 percent in each eye with or without punctal plugs in place. Blood pressure, resting pulse rate, and intraocular pressure were measured both before timolol instillation and at intervals of 1, 2, 4, 8, and 12 hours following drop instillation. Following a 2-week washout period, the subjects were evaluated with the alternative treatment. RESULTS: There was no statistically significant difference (p = 0.648) in IOP levels between treatment groups. CONCLUSIONS: This pilot suggests that need for a longer-term study with larger numbers of subjects to evaluate the potential role of silicone punctal plugs to enhance the ocular bioavailability of topically applied antiglaucoma medications.