Molecular Recognition of Tyrosine-Containing Polypeptides with Pseudopeptidic Cages Unraveled by Fluorescence and NMR Spectroscopies

The molecular recognition of Tyr-containing peptide copolymers with pseudopeptidic cages has been studied using a combination of fluorescence and NMR spectroscopies. Fluorescence titrations rendered a reasonable estimation of the affinities, despite the presence of dynamic quenching masking the unambiguous detection of the supramolecular complexes. Regarding NMR, the effect of polypeptide (PP) binding on relaxation and diffusion parameters of the cages is much more reliable than the corresponding chemical shift perturbations. To that, purification of the commercial PPs is mandatory to obtain biopolymers with lower polydispersity. Thus, the relaxation/diffusion-filtered 1H spectra of the cages in the absence vs presence of the PPs represent a suitable setup for the fast detection of the noncovalent interactions. Additional key intermolecular NOE cross-peaks supported by molecular models allow the proposal of a structure of the supramolecular species, stabilized by the Tyr encapsulation within the cage cavity and additional attractive polar interactions between the side chains of cage and PP, thus defining a binding epitope with a potential for implementing sequence selectivity. Accordingly, the cages bearing positive/negative residues prefer to bind the peptides having complementary negative/positive side chains close to the target Tyr, suggesting an electrostatic contribution to the interaction. Overall, our results show that both techniques represent a powerful and complementary combination for studying cage-to-PP molecular recognition processes.

Pseudopeptidic Host Adaptation in Peptide Recognition Unveiled by Ion Mobility Mass Spectrometry

The complexation of the glutamic-tyrosine-glutamic tripeptide (EYE) with a series of pseudopeptidic cages has been thoroughly investigated using different analytical techniques. Stoichiometry and affinities of the supramolecular host : guest...

Molecular cages for biological applications

Artificial receptors able to recognise biologically relevant molecules or ions have gained interest in the chemical community because they offer a plethora of posibilities. Molecular cage compounds are polycyclic compounds with a cavity designed for the encapsulation of guest species. Once inside the host cavity, the substrate can be transported through membranes and protected from the action of enzymes or other reactive species, thus offering the possibility of interfering with biological systems. Commonly, enzymes have been an inspiration for chemists in the search and design of defined cavities for different purposes. However, the chemical preparation of molecular cages has struggled with many synthetic challenges but this effort is worthwhile as they are a very promising tool for many applications ranging from sensing, delivery, purification or even promotion of/prevention from chemical modifications. Since the early reports at the end of the 60s, this field has experienced a growing interest; this review summarises the progress in the preparation and study of cage-like compounds highlighting their importance in biological applications.

Modulation of Src Kinase Activity by Selective Substrate Recognition with Pseudopeptidic Cages

The selective recognition of tyrosine residues in peptides is an appealing approach to inhibiting their tyrosine kinase (TK)-mediated phosphorylation. Herein, we describe pseudopeptidic cages that efficiently protect substrates from the action of the Src TK enzyme, precluding the corresponding Tyr phosphorylation. Fluorescence emission titrations show that the most efficient cage inhibitors strongly bind the peptide substrates with a very good correlation between the binding constant and the inhibitory potency. Structural insights and additional control experiments further support the proposed mechanism of selective supramolecular protection of the substrates. Moreover, the approach also works in a completely different kinase-substrate system. These results illustrate the potential of supramolecular complexes for the efficient and selective modulation of TK signaling.

Lymphedema: A General Outline of Its Anatomical Base

The anatomic research of the lymphatic system has been a very controversial subject throughout due to the complexity of the methods for its visualization. More than 30 years ago, together with Prof. Caplan, we began the vascular anatomy research, focusing on the lymphatic anatomy, developing and adapting different techniques of injection. On the third Normal Anatomy Chair of Buenos Aires University, we summarized the lymphatic drainage of the breast and the limbs to interpret the anatomic bases of lymphedema.

Retromer-dependent neurotransmitter receptor trafficking to synapses is altered by the Parkinson's disease VPS35 mutation p.D620N

Vacuolar protein sorting 35 (VPS35) is a core component of the retromer complex, crucial to endosomal protein sorting and intracellular trafficking. We recently linked a mutation in VPS35 (p.D620N) to familial parkinsonism. Here, we characterize human VPS35 and retromer function in mature murine neuronal cultures and investigate neuron-specific consequences of the p.D620N mutation. We find VPS35 localizes to dendritic spines and is involved in the trafficking of excitatory AMPA-type glutamate receptors (AMPARs). Fundamental neuronal processes, including excitatory synaptic transmission, AMPAR surface expression and synaptic recycling are altered by VPS35 overexpression. VPS35 p.D620N acts as a loss-of-function mutation with respect to VPS35 activity regulating synaptic transmission and AMPAR recycling in mouse cortical neurons and dopamine neuron-like cells produced from induced pluripotent stem cells of human p.D620N carriers. Such perturbations to synaptic function likely produce chronic pathophysiological stress upon neuronal circuits that may contribute to neurodegeneration in this, and other, forms of parkinsonism.

Cellular mechanisms against ischemia reperfusion injury induced by the use of anesthetic pharmacological agents

Ischemia-reperfusion (IR) cycle in the myocardium is associated with activation of an injurious cascade, thus leading to new myocardial challenges, which account for up to 50% of infarct size. Some evidence implicates reactive oxygen species (ROS) as a probable cause of myocardial injury in prooxidant clinical settings. Damage occurs during both ischemia and post-ischemic reperfusion in animal and human models. The mechanisms that contribute to this damage include the increase in cellular calcium (Ca(2+)) concentration and induction of ROS sources during reperfusion. Pharmacological preconditioning, which includes pharmacological strategies that counteract the ROS burst and Ca(2+) overload followed to IR cycle in the myocardium, could be effective in limiting injury. Currently widespread evidence supports the use of anesthetics agents as an important cardioprotective strategy that act at various levels such as metabotropic receptors, ion channels or mitochondrial level. Their administration before a prolonged ischemic episode is known as anesthetic preconditioning, whereas when given at the very onset of reperfusion, is termed anesthetic postconditioning. Both types of anesthetic conditioning reduce, albeit not to the same degree, the extent of myocardial injury. This review focuses on cellular and pathophysiological concepts on the myocardial damage induced by IR and how anesthetic pharmacological agents commonly used could attenuate the functional and structural effects induced by oxidative stress in cardiac tissue.

Ca2+Permeability of the (α4)3(β2)2Stoichiometry Greatly Exceeds That of (α4)2(β2)3Human Acetylcholine Receptors

Human alpha4beta2 nicotinic acetylcholine receptors (AChRs) expressed in Xenopus laevis oocytes or transfected cell lines are present as a mixture of two stoichiometries, (alpha4)2(beta2)3 and (alpha4)3(beta2)2, which differ depending on whether a beta2 or alpha4 subunit occupies the accessory subunit position corresponding to beta1 subunits of muscle AChRs. Pure populations of each stoichiometry can be expressed in oocytes by combining a linked pair of alpha4 and beta2 with free beta2 to produce the (alpha4)2(beta2)3 stoichiometry or with free alpha4 to produce the (alpha4)3(beta2)2 stoichiometry. We show that the (alpha4)3(beta2)2 stoichiometry and the (alpha4)2(beta2)2beta3 and (alpha4)2(beta2)2alpha5 subtypes in which beta3 or alpha5occupy the accessory positions have much higher permeability to Ca2+ than does (alpha4)2(beta2)3 and suggest that this could be physiologically significant in triggering signaling cascades if this stoichiometry or these subtypes were found in vivo. We show that Ca2+ permeability is determined by charged amino acids at the extracellular end of the M2 transmembrane domain, which could form a ring of amino acids at the outer end of the cation channel. Alpha4, alpha5, and beta3 subunits all have a homologous glutamate in M2 that contributes to high Ca2+ permeability, whereas beta2 has a lysine at this position. Subunit combinations or single amino acids changes at this ring that have all negative charges or a mixture of positive and negative charged amino acids are permeable to Ca2+. All positive charges in the ring prevent Ca2+ permeability. Increasing the proportion of negative charges is associated with increasing permeability to Ca2+.

[Anticholinesterases in the treatment of Alzheimer's disease]

INTRODUCTION

Among the numerous pathophysiological theories that attempt to explain the development of Alzheimer's disease (AD) there are two facts that stand out above the rest: on the one hand, the formation of neurofibrillary tangles inside cells and, on the other, the extra-cellular deposition of beta-amyloid protein. These two mechanisms lead to neurodegeneration and the death of cells by means of a process called 'apoptosis' or 'programmed cell death'. In the early stages of this neurodegenerative process it is more pronounced in cholinergic-type brain centres. This led to the formulation of the so-called cholinergic theory of Alzheimer, which provides the rationale behind the use of the drugs that are currently available to treat this disease, namely, acetylcholine esterase (AChE) inhibitors (rivastigmine, donepezil and galanthamine).

DEVELOPMENT AND CONCLUSIONS

We review the possible pharmacological approaches that could help to prevent or delay cell death, and which act on the mechanisms involved in the production of neurofibrillary tangles or the deposition of beta-amyloid protein. We also review the main characteristics of cholinergic neurotransmission, which will help us to understand the therapeutic approaches that have been applied in an attempt to enhance deficient cholinergic neurotransmission. One of the most notable of these is the amount of attention recently being paid to the enzyme AChE, which increases the bioavailability of the neurotransmitter in the cholinergic synapses by preventing the hydrolysis of acetylcholine; these are the only drugs currently available for the symptomatic treatment of this disease.

Copper overload affects copper and iron metabolism in Hep-G2 cells

Divalent metal transporter #1 (DMT1) is responsible for intestinal nonheme Fe apical uptake. However, DMT1 appears to have an additional function in Cu transport in intestinal cells. Because the liver has an essential role in body Cu homeostasis, we examined the potential involvement of Cu in the regulation of DMT1 expression and activity in Hep-G2 cells. Cells exposed to 10 microM Cu exhibited a 22-fold increase in Cu content and a twofold decrease in Fe content compared with cells maintained in 0.4 microM Cu. (64)Cu uptake in Cu-deficient Hep-G2 cells showed a twofold decrease in K(m) compared with cells grown in 10 microM Cu. The decreased K(m) may represent an adaptive response to Cu deficiency. Cells treated with >50 microM Cu, showed an eightfold increase in cytosolic metallothionein. DMT1 protein decreased (35%), suggesting that intracellular Cu caused a reduction of DMT1 protein levels. Our data indicate that, as a result of Cu overload, Hep-G2 cells reduced their Fe content and their DMT1 protein levels. These findings strongly suggest a relationship between Cu and Fe homeostasis in Hep-G2 cells in which Cu accumulation downregulates DMT1 activity.

Metallothionein is crucial for safe intracellular copper storage and cell survival at normal and supra-physiological exposure levels

MTs (metallothioneins) increase the resistance of cells to exposure to high Cu (copper) levels. Characterization of the MT-Cu complex suggests that MT has an important role in the cellular storage and/or delivery of Cu ions to cuproenzymes. In this work we investigate how these properties contribute to Cu homoeostasis by evaluating the uptake, accumulation and efflux of Cu in wild-type and MT I/II null rat fibroblast cell lines. We also assessed changes in the expression of Cu metabolism-related genes in response to Cu exposure. At sub-physiological Cu levels (0.4 microM), the metal content was not dependent on MT; however, when extracellular Cu was increased to physiological levels (10 microM), MTs were required for the cell's ability to accumulate the metal. The subcellular localization of the accumulated metal in the cytoplasm was MT-dependent. Following supra-physiological Cu exposure (>50 microM), MT null cells had a decreased capacity for Cu storage and an elevated sensitivity to a minor increment in intracellular metal levels, suggesting that intracellular Cu toxicity is due not to the metal content but to the interactions of the metal with cellular components. Moreover, MT null cells failed to show increased levels of mRNAs encoding MT I, SOD1 (superoxide dismutase 1) and Ccs1 (Cu chaperone for SOD) in response to Cu exposure. These results support a role for MT in the storage of Cu in a safe compartment and in sequestering an intracellular excess of Cu in response to supra-physiological Cu exposure. Gene expression analysis suggests the necessity of having MT as part of the signalling pathway that induces gene expression in response to Cu.

Copper exposure modifies the content and distribution of trace metals in mammalian cultured cells

With this work, we have determined the cellular content of Cu, Fe and Zn in different cell lines, by using total reflection X-ray fluorescence spectrometry (TXRF). In addition, we examined whether cellular exposure to 100 micromoles l(-1) of Cu-His modifies the intracellular content and distribution of these trace metals. Our results indicate that all the cell lines displayed the same pattern of relative intracellular abundance of trace metals (Cu<Fe<Zn). This pattern shifted to Fe<Zn<Cu, when extracellular copper concentration was increased. In HepG2 and Caco2 cells, copper exposure increased intracellular copper content while Fe and Zn decreased. Regarding cellular distribution of trace metals, they decreased in the cytosol fraction of HepG2 cells, after exposure to copper. Therefore, our results indicate that cellular adaptation to copper involves a new balance in the relative abundance of trace metals and induces changes in the cellular distribution of Cu, Zn and Fe.

Tau-like proteins associated with centrosomes in cultured cells

The subcellular association of tau-like proteins with centrosomes in cultured cell lines and its effects in nucleating microtubule assembly were analyzed using biochemical and immunocytochemical approaches. Tau proteins, major components of microtubules, appear to be tightly associated with actin filaments in a variety of cell lines, while in pathological conditions of neurons, they are part of paired helical filaments found in Alzheimer's disease. Different studies suggest that, in addition to tau interactions with the components of the cytoskeletal network, tau polypeptides appear to be associated with highly structured cellular elements, in both interphase and mitotic cells. An in-depth analysis of tau subcellular distribution us- ing different polyclonal and monoclonal antibodies showed colocalization of tau-like components with centrosomes in interphase cells of the human Huh-7 hepatoma, in SW-13 adenocarcinoma, and in normal human fibroblasts. Tau associated with centrosomes in mitotic Huh-7 cells was also identified. However, antibodies against the tau binding repeats did not stain centrosomes. A set of different tau isoforms was also identified by Western blot analysis on isolated centrosomal preparations from Huh-7 cells, obtained by differential centrifugation through sucrose gradients. Microtubule nucleation in vitro over isolated centrosomes was inhibited by both the polyclonal antibody against native tau and an antibody to the N-terminal tau sequence, as revealed by immunofluorescence analysis and assembly kinetics experiments. The antibody TRS1.2 against the fragment containing the first binding repeat on tau did not affect nucleation. These studies allowed us to characterize tau association with the isolated centrosomal preparation and its involvement in microtubule assembly nucleated over centrosomes, thus suggesting possible structural and functional roles for these interactions.

Extracellular matrix regulates the amount of the beta-amyloid precursor protein and its amyloidogenic fragments

We have studied the influence of the extracellular matrix (ECM) on the amount of beta-amyloid precursor protein (APP) and C-terminal amyloid-bearing fragments in 313 fibroblasts. After incubation with ECM components, the cellular APP content of 3T3 cells changed. Besides, different substrata including collagen, fibronectin, laminin, vitronectin, and heparin, determined changes in the amount of a C-terminal 22 kDa-fragment. The regulation of amyloidogenic fragments by the ECM was transient; in fact, when 3T3 cells were plated on tissue culture dishes coated with collagen or vitronectin, maximal levels of the 22 kDa fragment were observed 12 h after plating; in the presence of fibronectin, the maximum level of the amyloidogenic fragment was obtained 36 h after plating. These results indicate that the ECM modulates in a transient way the generation of APP-derived polypeptides containing the amyloid-beta-peptide (A beta). The ECM does not have a generalized effect on 3T3 fibroblasts, because no significant differences in cell attachment, growth rate, whole-cell polypeptide pattern beta 1 integrin and alpha-tubulin levels were observed on cells grown on various matrix proteins. Laminin, collagen, and heparin also influence the level of an amyloidogenic fragment of 35 kDa in Neuro 2A neuronal cells, without a significant change in the neuronal marker acetylcholinesterase. In this case, however, a long-lasting response to ECM molecules was observed. These observations provide evidence that ECM molecules influence APP biogenesis, including the generation of amyloidogenic fragments containing the A beta peptide. Our studies might prove significant to understand the localized increment of beta-amyloid deposition in selected areas of the brain of Alzheimer's patients.

Functional organization of tau proteins during neuronal differentiation and development

Tau proteins play major regulatory roles in the organization and integrity of the cytoskeletal network. In neurons, a specific axonal compartmentalization of tau has been shown. However, recent studies demonstrate that tau displays a widespread distribution in a variety of non-neuronal cell types. These proteins have been found in human fibroblasts and in several transformed cell lines. The heterogeneous family of tau is formed by a set of molecular species that share common peptide sequences. There is a single gene that contains several exons encoding for the six different tau isoforms in mammalian brain. Alternative splicing of a common RNA transcript as well as post-translational modifications contribute to its heterogeneity. Tau isoforms generated by splicing differ from one another by having either three or four repeats in their C-terminal half, and a variable number of inserts in their N-terminal moiety. These repeats have been shown to constitute microtubule-binding motifs. In this review some relevant aspects of tau function and its regulation are analyzed. Three major topics are discussed. The first one focuses on the tau roles in regulating the interactions between microtubules with actin filaments and with intermediate filament systems. Another problem deals with the question of whether tau isoforms segregate into functionally different subsets of microtubules in axonal processes, or tau associates with these polymers in a random fashion. The third question that emerges is the involvement of tau and tau-like proteins in morphogenetic events. The regulation of the interactions of DMAP-85, a recently discovered tau-like protein, with the cytoskeleton during development of Drosophila melanogaster is analyzed.

An escalating dose regime of recombinant interferon-alpha 2A in the treatment of chronic hepatitis C

Interferon-alpha (IFN-alpha) has proven useful in the treatment of chronic hepatitis C, but a relapse in response is frequently observed. The possible benefit of daily administration of recombinant IFN-alpha 2A at an escalating (from 1.5 to 9 MU) regime depending on the evolution of serum aminotransferase (ALT) levels was evaluated in 31 adult patients with chronic hepatitis C. At the end of the first month with 1.5 MU of rIFN-alpha 2A, 9/31 (29%) had normal ALT values. Then, 22 patients were given 3 MU daily and at the second month 4 patients (18%) normalized ALT values. The 18 non-responders received 6 MU and 4 of them (22%) normalized ALT values (1 patient dropped out). Finally, the remaining 13 non-responders were given 9 MU and in 4 (30%) ALT fell to normal ranges. Three non-responders to 1.5 MU normalized ALT values when the dose of rIFN-alpha 2A was increased (n = 2, 3 MU; n = 1, 9 MU). The overall response achieved was 68%. Within 3 months after cessation of treatment, 12/20 (60%) responder patients had a relapse in ALT levels. Therefore, although daily administration of rIFN-alpha 2A does not improve the results obtained with a thrice-weekly schedule, a proportion of non-responders could benefit from an escalating dose to a high amount (63 MU/week) of rIFN-alpha 2A.

Treatment of chronic hepatitis C by continuous subcutaneous infusion of interferon-alpha

The effectiveness of a daily continuous infusion of interferon-alpha was evaluated in 12 patients (10 males, 2 females; mean age of 33 years, range 19-62) with biopsy-proven chronic active hepatitis C. Nine million units (MU) of recombinant interferon-alpha 2A (rIFN-alpha 2A) were administered by continuous subcutaneous infusion with a portable syringe pump, Graseby model MS 16A, for 24 h over 28 days. A significant decrease (P less than 0.01) in median serum alanine aminotransferase (ALT) levels was observed after the first week of treatment (96 IU/L, range 58-263) with respect to the pre-treatment values (188 IU/L, range 119-670). ALT became normal in four patients only by the fourth week. When IFN was interrupted, an increase in ALT was observed in all patients (1.5 to 5 times the pre-treatment values). The maximum decrease in ALT coincided with a significant increase in serum levels of the enzyme 2',5'-oligoadenylate (2-5A) synthetase (two to fourteen times the pretreatment values) and these parameters were inverse-correlated (r = -0.598, P less than 0.05). 2-5A synthetase levels returned to pre-treatment values after discontinuing IFN administration. Hepatitis C virus (HCV) RNA (as detected by the polymerase chain reaction using oligonucleotide primers of the NS5 region) was positive in all cases, remaining so during the treatment period. IgM antibody to HCV (as tested by ELISA) was present in 10/12 cases at baseline without changes throughout the study. No irreversible side effects were noted during therapy, which needed to modify the schedule.(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic lupus erythematosus in patients with end-stage renal disease: long-term follow-up on the prognosis of patients and the evolution of lupus activity

We studied the clinical course of 59 lupus patients with end-stage renal disease (ESRD) to determine their long-term prognosis and delineate the evolution of their lupus activity. The study population was predominantly female (86%) and young (mean age, 27.4 years), and they were observed for a mean of 6.5 years from the inception of dialysis. At the time dialysis was initiated, only 21 patients (35.6%) had clinically active systemic lupus erythematosus (SLE). The remaining patients progressed to ESRD despite the absence of clinical lupus activity. Lupus activity was clinically apparent in 55.4% of patients in the first year, 6.5% in the fifth, and none in the tenth year. In 45% of patients, lupus activity was clinically inactive at entry to ESRD and remained inactive throughout the observation period. Serological activity declined proportionally, but to a lesser extent than clinical activity. Cumulative patient survival was 81.1% and 74.6% at the fifth and tenth year, respectively, from the inception of dialysis treatment; similarly it was 78% at the fifth and tenth year after the transplantation. Graft survival was 60.4% at the fifth and 45.5% at the tenth year. No one had recurrence of clinical lupus nephritis in the graft for up to 16 years of follow-up. Fourteen patients died from either infectious or cardiovascular complications, but none from SLE per se. This long-term study with a large number of lupus patients confirms our previous findings that the progression of renal disease to ESRD may be mediated by nonimmunologic mechanisms, as well as immunologic insults.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertension in kidney transplant recipients. Effect on long-term renal allograft survival

To examine the effects of hypertension on renal graft function, we studied the clinical course of 144 kidney transplant recipients who had functioning grafts for three to 13 years. The patients were divided into three groups: normotensive (n = 32), controlled hypertensive (n = 49) and uncontrolled hypertensive group (n = 63). In addition to the difference in their blood pressure status, the three groups had significantly different levels of serum creatinine at entry to the study (mean +/- SE in mg/dL: 1.41 +/- 0.02, 8.89 +/- 0.02 and 2.30 +/- 0.03, respectively, P = .0002). Cumulative graft survival (CGS) at ten years for normotensive patients was 81%, whereas it was 58% for controlled hypertensive patients and 50% for uncontrolled hypertensive patients. The difference of CGS between normotensive and hypertensive patients was significant (P = .01), whereas the difference between the two hypertensive groups, controlled v. uncontrolled, was not. If serum creatinine levels at entry to the study were adjusted and the CGS of hypertensive patients was compared to normotensive patients with comparable levels of serum creatinine, the differences in CGS between the two groups were no longer significant. Regression analyses for potential prognostic factors revealed that serum creatinine levels were of more primary importance as a prognostic variable than blood pressure status. We conclude that hypertension is an important risk factor for renal graft survival, but control of hypertension alone does not appear to improve it. Graft survival appears to be influenced more by the severity of graft dysfunction at entry to the study irrespective of blood pressure control.

Kidney transplantation in insulin dependent diabetic patients: improved survival and rehabilitation

Between 1977 and 1986, 50 insulin-dependent diabetic patients received a kidney transplant, 19 from living related donors and 31 from cadaveric donors. Cumulative patient survival was 81% and graft survival was 64% and 33% for living related and cadaveric donor kidneys, respectively, at five years. These results are comparable to that of nondiabetic patients. While physical performance and visual acuity significantly improved after a successful kidney transplantation, neuropathies and angiopathies might not improve. Physical performance improved even in those patients whose nerve conduction time had deteriorated. These findings suggest that kidney transplantation is an effective means of improving survival and rehabilitation of diabetic patients with end-stage renal disease.

[Liaison psychiatry: a new perspective on mental health in Latin America]

The situation of Mental Health in Latin America is analyzed. Urgently creating a system able at handling the psychiatric disease increase in the years to come is a conclusion this paper strongly aims at. The beginning of Psychiatry is reviewed, and the importance of Psychiatry at the General Hospital is outlined as well as its rapprochement toward the community, which led to a better control and prevention in the field of Mental Health. A definition of Psychiatry is proposed, as a branch of Medicine which stands in between mental hospitals and communities. Active teamwork, coupled with the physician's work and the tasks other members of the health personnel are engaged in, has led to a more integrated approach onto the ill thus benefiting not only patients but also the whole community.

Photosynthetic Gas Exchange Characteristics of Wheat Flag Leaf Blades and Sheaths during Grain Filling: The Case of a Spring Crop Grown under Mediterranean Climate Conditions

The rate of net CO(2) assimilation (A), the stomatal (g(s)) and residual (g(r)) conductances to CO(2), the intercellular CO(2) concentration, the CO(2) compensation points at 21% O(2) (Gamma(21)) and at 2% O(2) (Gamma(2)), and the amounts of dry matter, nitrogen, and carbohydrates were determined, from anthesis through grain filling, in the flag leaf blade and sheath of spring wheat (Triticum aestivum L. cv Kolibri). The nitrogen content and the rate of net CO(2) assimilation declined slowly until the onset of senescence in both organs, about 3 weeks after anthesis. During senescence the reduction of A in both organs was not primarily caused by a decrease in g(s); the main factor is the decrease in g(r). From values of Gamma(21) and Gamma(2) it is suggested that the rate of respiration in the light contributing to the CO(2) compensation point is higher in sheaths than in blades irrespective of the O(2) level considered. The role of sheaths storing and later transporting assimilates to the developing grains seems to be more important for shoot yield than that of sheaths functioning as photosynthetic organs after the onset of senescence occurs. It is suggested that accumulation of carbohydrates in leaves might somehow trigger senescence in the flag leaf blade and sheath simultaneously.

Invasive trichophyton rubrum infection in an immunocompromised host. Case report and review of the literature

Typically confined within the keratinized, epithelial layer of the skin and hence categorized among the dermatophytoses, Trichophyton rubrum infections usually present as superficial, scaling eruptions. In certain clinical settings, however, such as in immunosuppressed hosts, deep local invasion, multivisceral dissemination, and even death due to T. rubrum granulomas have been described. A case of multiple, subcutaneous, neutrophilic abscesses due to T. rubrum in an immunosuppressed renal allograft recipient is described. The pathogenesis, diagnosis, and immunology of invasive T. rubrum infections in immunocompromised hosts are reviewed.

Ontogenetic changes in photosynthetic capacity and dry matter production of flag wheat leaves during the grain filling period

The relationships between photosynthetic capacity and dry matter accumulation during the grain filling period have been studied in flag leaves of Triticum aestivum L., cv. Kolibri grown in Mediterranean field conditions. Particular importance has been given to assimilate accumulation in relation to the onset of senescence. During grain filling, the time course of specific dry weight (SDW) was similar in the blade and in the sheath. Variations in SDW were about six times larger in the sheath than in the blade. Minimum blade SDW values occurred during heading and at anthesis. Maximum blade SDW values were observed two weeks after anthesis. After this, SDW values decreased sharply. The dry matter increase per grain in the period from two weeks after anthesis to the end, was only about 25% of final grain dry weight. The importance of environmental constraints on maximum SDW values are discussed. Maximum SDW values occurred at the beginning of the period of rapid decline in blade net CO2 assimilation rate and leaf nitrogen content, that is, at the beginning of senescence. On the other hand, the stomatal resistance to CO2 and the development of senescence are not apparently related. The maximum blade dry weight increase (considering a value of zero at heading) was about 60 mg dry weight per g fresh weight. The possible relationships between dry matter accumulation and senescence onset are discussed.

Focal segmental glomerulosclerosis in renal transplants

This is a study of the incidence and clinicopathological significance of focal segmental glomerulosclerosis (FSG) in 154 renal allografts (22 biopsies, 128 nephrectomies and four necropsies) from 137 cadaveric and 17 living-related donors. FSG was identified in 18 grafts (11.7%) from 16 patients: six as recurrent FSG in four patients (two developed FSG in two consecutive transplants) and 12 as de novo FSG. The incidence of recurrent FSG in patients who had FSG as their original kidney disease was 30.8% whereas that of de novo FSG in patients who had renal diseases other than FSG was 8.7%. Histologically, recurrent FSG was characterized by mild degrees of obliterative arteriopathy of rejection and preferential involvement of the juxtamedullary glomeruli. Whereas, in de novo FSG, the occlusive vascular changes of rejection were severe and the glomeruli in the outer cortical region were mostly involved. Clinically, however, the differences between them were less clear, although nephrotic syndrome tends to occur more often and earlier in patients with recurrent FSG. Obliterative arteriopathy of chronic rejection and consequent glomerular ischemia appeared to be of major importance in the pathogenesis of de novo FSG in renal allografts.

Percutaneous transluminal dilation in renal transplant arterial stenosis

Twelve hypertensive patients underwent percutaneous transluminal dilation (PTD) for relief of arterial stenosis complicating renal allotransplantation. Two patients underwent repeat PTD for recurrent stenosis and hypertension. Six patients had end to end anastomosis of the donor renal artery to the recipient hypogastric artery; four of six PTDs were successful. Six patients had end to side anastomosis of the donor renal artery to the recipient external iliac artery; seven of eight PTDs, including one of two repeat PTDs, were successful. Prior to PTD, all patients were using several antihypertensive medications. Following successful PTD, the mean blood pressure dropped from 184 +/- 15/118 +/- 9 to 133 +/- 13/89 +/- 11 mm Hg (P < 0.001) and remained at that level for up to 15 months (average followup 9 months) with decreased or no antihypertensive medications. Since surgical correction of arterial stenosis occurring after renal transplantation is difficult and may endanger the graft, PTD should be the first interventional therapy.

Kidney transplant nephrotic syndrome: relationship between allograft histopathology and natural course

We analyzed clinical and pathologic data from 36 recipients of 38 renal allografts who developed nephrotic syndrome following transplantation. Three groups were identified on the basis of histologic changes in the graft, and each group had a distinct clinical course. Nine grafts (23.7%) had recurrent glomerulonephritis (GN) (5 membrano-proliferative, 4 focal glomerulosclerosis) and developed nephrotic syndrome at 5.1 months (mean) posttransplant. Renal function deteriorated rapidly, with a 2-year graft survival of 29.7%. Four grafts (10.5%) with de novo GN (3 epimembranous, 1 minimal change) developed nephrotic syndrome at 32 months posttransplant, and all functioned for more than 3 years. Twenty-five grafts (65.8%) had allograft glomerulopathy with the onset of nephrotic syndrome at 9.1 months posttransplant and a 2-year graft survival of 66.6%. The differences in duratin of graft function between grafts with allograft glomerulopathy and recurrent GN (P < 0.01) and in graft survival rates at 2 years among the three groups (P < 0.05) are statistically significant. This analysis indicates that allograft glomerulopathy is the most common cause of kidney transplant nephrotic syndrome. Membranoproliferative GN and focal glomerulosclerosis may recur soon after transplantation and rapidly progress to renal failure in marked contrast to grafts with either de novo epimembranous nephropathy or minimal glomerular change, lesions that are compatible with prolonged graft function.

Percutaneous transluminal angioplasty in renal transplant arterial stenosis for relief of hypertension

Seven hypertensive patients underwent percutaneous transluminal angioplasty (PTA) for relief of arterial stenosis complicating renal allotransplantation. Four had end-to-end anastomosis of the donor renal artery to the recipient hypogastric artery; all PTA's were successful. Three patients had end-to-side anastomosis of the donor renal artery to the recipient external iliac artery; 2/3 PTA's were successful. Prior to PTA, all patients were using several antihypertension medications. Following successful PTA, the mean blood pressure fell from 190 +/- 10/120 +/- 5 to 132 +/- 16/86 +/- 9 mm Hg (p less than 0.01) and remained at that level for up to six months (average follow-up 2.85 months) with decreased or no antihypertension medications. Since surgical correction of arterial stenosis is difficult and may endanger the transplant kidney, PTA should be attempted first.

Association between Streptococcus faecalis urinary infections and graft rejection in kidney transplantation

In the first month after transplantation 50% of 193 consecutive renal transplant recipients had bacteriuria. The most common organisms isolated were Streptococcus faecalis (34), Escherichia coli (28), Pseudomonas spp. (11), and staphylococcus (9). There was a significant correlation between infection with Str. faecalis and graft failure at one, three, and twelve months. This observation suggests that urinary infection with Str. faecalis may be associated with graft failure which is probably the result of immunological factors.

Anaerobic bacteriuria in renal transplantation

Renal allograft recipients were studied prospectively utilizing improved culture techniques to investigate anaerobic bacteriuria. The study population was compared with a population of patients with chronic renal insufficiency and end stage renal disease. The over-all incidence of anaerobic urinary tract infection was 7.5 per cent while the over-all incidence of aerobic urinary tract infection was 23.5 per cent. Patients with cadaver renal transplants during the early postoperative period had the highest incidnece of both anaerobic (42.9 per cent) and aerobic (71.4 per cent) urinary tract infection of all groups. The potential association between significant anaerobic bacteriuria during the first postoperative month and poor prognosis for cadaver renal allografts merits further investigation.

Renal allograft fracture: clinicopathological study of 21 cases

Experience with renal allograft fracture occurring in 21 of 246 transplants performed over a 29-month period is reviewed. Clinical manifestations included pain and tenderness at the graft site, fever, and falling hematocrit. The fracture occurred without exception in the course of an acute rejection episode. Diagnosis was made from two days to seven weeks following transplantation; in 13 patients (62%) diagnosis was made within two weeks of surgery. Severe damage to the kidney necessitated nephrectomy in all but two transplants. Of those not removed at initial exploration only one regained function to permit a dialysis-free existance for several months. Histologic examination of the fractured kidneys revealed the pathogenesis to be acute rejection in 13 (62%), accelerated acute rejection in four (19%), and a combination of these processes in four (19%). Conclusions from this study are that fractures of renal allografts: (1) are more frequent than commonly realized; (2) are primarily due to the swelling of acute rejection; (3) are often characterized by sudden onset of pain in the region of the graft accompanied by fever and falling hematocrit; (4) should be treated by prompt surgical intervention to control hemorrhage, to perform nephrectomy if indicated, and to evacuate the hematoma in order to reduce the possibility of secondary infection.