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Biomedical subjects

C S Jenkins

Publications and source records attributed to C S Jenkins.

At least 19 recordsLinked to original sources
PubMed1988

Psychopathology of chronic haemodialysis: is it a behavioural cognitive continuum?

Neuropsychiatric complications of chronic renal haemodialysis cover a wide gamut of clinical syndromes. These pictures can be diagnostically classified as non-psychotic and psychotic-like syndromes. On the basis of a review of the literature, some nosological precisions are formulated, and a hypothesized cognitive-behavioural psychopathological continuum is presented. The hypothesis postulates that a central cognitive disturbance, due to multiple organic aetiopathogenic factors, results in a step-wise decline, initially disguised as an affective, neurotic or personality disorder, and further deteriorating into the well-known "dialysis dementia", with a variety of other clinical presentations in between. Additional research in the biological and psychosocial areas is needed to verify different aspects of these conditions, their validity in the context of the authors' hypothesis, and their relevance to the overall "quality of life" of chronic haemodialysis patients.

Cognition Disorders↗
PubMed1986

Fibronectin synthesis and degradation in human fibroblasts with aging.

Fibronectin was measured in early and late passaged human skin fibroblasts utilizing immunoprecipitation and polyacrylamide gel electrophoresis. A progressive increase in the rate of fibronectin and total cellular protein synthesis per cell was observed by late passaged human diploid fibroblasts. The absolute protein concentration increased in the late passaged fibroblasts. There was no significant difference in the [3H]leucine incorporation into fibronectin or total cellular protein/mg protein. The turnover of fibronectin and total cellular protein did not differ between early and late passaged fibroblasts. The transport of fibronectin to the cell membrane was similar in late passaged fibroblasts. The increased fibronectin synthesis in senescent fibroblasts appeared to correlate with the general increase in rate of protein synthesis/cell.

Cell Survival↗
PubMed1985

Platelet cytoskeleton alpha-actinin in normal and thrombasthenic platelets: distribution and immunologic characterization.

The subcellular localization of alpha-actinin (Mr 100,000) in human skeletal muscle is restricted to the Z line, in which it is believed to anchor actin filaments. Recently, this protein was identified in normal and thrombasthenic human platelets by its antigenic cross-reaction with antibodies to chicken gizzard alpha-actinin. In our study, the biochemical interaction between purified platelet alpha-actinin and striated muscle F-actin was examined by electron microscopy of negatively stained preparations. Like its muscle counterpart, platelet alpha-actinin promotes the cross-linking and bundling of actin filaments. Antibodies prepared to human platelet alpha-actinin cross-reacted with chicken gizzard alpha-actinin as shown by immunoelectrophoresis and the western blotting technique. Immunoblots prepared with normal and thrombasthenic platelets with antibodies to human platelet alpha-actinin revealed that this protein is susceptible to proteolysis. Extracts of freshly drawn platelets showed a protein band of 100 K. When the platelet extracts were incubated at 37 degrees C for various times, the immunoblots showed protein bands of 100 and 80 K. The proportion of the 80 K protein band increased with incubation time. This proteolysis can be prevented by chelating agents such as EDTA or the protease inhibitor leupeptin. Indirect immunofluorescent studies of human skin fibroblasts with antibodies to chicken gizzard actin and human skeletal muscle, chicken gizzard, and platelet alpha-actinin revealed the staining pattern characteristic of each protein. The distribution of alpha-actinin in normal and thrombasthenic platelets was assessed by ferritin-labeled immunoelectron microscopy. Ferritin particles were found in the cytoplasm immediately below the membrane and in some granules. There was no labeling associated with the mitochondria.

Actinin↗
PubMed1979

Spontaneous platelet aggregation in cerebrovascular disease II. Further characterisation of the platelet defect.

A group of 186 patients with Transient Ischaemic Attacks (TIA) or cerebral infarction (CI) was found to demonstrate in vitro Spontaneous Platelet Aggregation (SPA) in 39% of those studied. Of the 176 normal subjects studied the incidence on in vitro SPA was found to be 5%. Further investigation of the phenomenon of SPA revealed that: 1. it is associated with ADP-hyperaggregability, i. e. the threshold concentration to induce second wave aggregation is decreased; 2. it is dependant on the increase in pH which occurs in platelet-rich plasma stirring in an aggregometer while concurrent ADP-hyperaggregability is independant of this change in pH; 3. it is associated with malondialdehyde production and the release of endogenous 5-hydroxytryptamine; and that 4. in addition Km and Vmax values for [14c]-5HT incorporation are normal; and that 5. no gross abnormalities of the platelet membrane glycoproteins were apparent although occasionally glycoprotein III was found to be increased. This study demonstrates abnormal platelet behaviour in patients with TIA and CI where the enzyme system involved in thromboxane production is sufficiently stimulated, by stirring alone, to induce aggregation of platelets and the release reaction. Acetylsalicylic acid abolishes SPA and prolongs the bleeding time with similar characteristics as has been described for normal individuals. Plasma beta-thromboglobulin levels are significantly increased in the patients studied. However, no correlation was established with the incidence of in vitro SPA.

Adenosine Diphosphate↗
PubMed1979

Acquired factor XII Deficiency in a patient with nephrotic syndrome.

A patient with nephrotic syndrome and an acquired factor XII deficiency associated with a factor XII-like procoagulant activity in the urine was investigated. The urinary protein with procoagulant activity was isolated and comparative investigations revealed similar properties to plasma factor XII. It is suggested that the acquired coagulation defect may result from an insufficient biosynthetic capacity to compensate for the loss of factor XII in the urine.

Adult↗
PubMed1979

Studies on the mechanism of ristocetin-induced platelet aggregation: binding of factor VIII to platelets.

The effect of ristocetin on the binding of [125I]factor VIII to platelets was studied. High and low affinity F.VIII binding sites exist on platelets. The high affinity sites bind 13 times more F.VIII than the low affinity sites. Ristocetin increased the binding of F.VIII to both types of binding sites by increasing the affinity of F.VIII for the platelet and increasing the total number of platelet binding sites. Chymotrypsin-treated platelets were not aggregated by ristocetin and F.VIII: these platelets have less of the major platelet membrane glycoproteins and bind much less [125I]F.VIII than do buffer-treated platelets with and without ristocetin.

Antigens↗
PubMed1979

Studies on the mechanism of ristocetin-induced platelet agglutination: binding of ristocetin to platelets.

Ristocetin was trace-labeled with [3H] by the reductive methylation method. It was shown to agglutinate human platelets in the presence of VIIIR:WF in a manner indistinguishable from unlabeled ristocetin. The binding of the labeled ristocetin to normal and enzyme-modified human platelets was studied both in the presence and absence of VIIIR:WF and at nonagglutinating and agglutinating concentrations of ristocetin. Virtually no difference in [3H]ristocetin binding was seen whether VIIIR:WF was present or not. Platelets treated with chymotrypsin, which destroys their ability to agglutinate to VIIIR:WF and ristocetin, did not bind less ristocetin than did control platelets. A pronounced, direct relationship was found between [3H]ristocetin bound by normal platelets and total ristocetin concentration. This implies that at the higher (agglutinating) concentrations of ristocetin either more binding sites are exposed or, more probably, aggregation of ristocetin occurs.

Alkylation↗
PubMed1978

Antithrombin-III transfusion in disseminated intravascular coagulation.

Three patients with a severe bleeding disorder and disseminated intravascular coagulation were effectively treated with human antithrombin-III concentrates. This treatment, followed by administration of prothrombin complex and platelet suspensions, resulted in a normal haemostasis, which was maintained during clinical investigations and surgery.

Adult↗
PubMed1978

Spontaneous platelet aggregation in cerebrovascular disease.

50 patients from a group of 130 patients with transient ischaemic attacks or cerebral infarction were found to demonstrate in vitro spontaneous platelet aggregation (SPA) while 80 normal subjects tested never showed this phenomenon. The following additional findings point towards a possible platelet abnormality: 1. Platelets from 10 patients with SPA when isolated and resuspended in normal plasma still demonstrated SPA while isolated normal platelets resuspended in patient's plasma did not. 2. Platelets demonstrating SPA showed an increased aggregation tendency upon incubation with ADP while normal platelets developed the expected refractory state. SPA was found to be dependant upon the presence of divalent cations and could further be inhibited by phentolamine and adenosine. Aspirin effectively abolished SPA in 50 patients and relieved the clinical symptoms of patients with recurrent complaints of transient blindness and paraesthesia.

Adenosine↗
PubMed1977

A comparative study of the effect of modification of the surface of human platelets on the receptors for aggregated immunoglobulins and for ristocentin-von Willebrand factor.

The receptors for aggregated immunoglobulin G (IgG) (an Fc receptor) and for ristocetin-von Willebrand factor on human platelets were studied by means of various modifications of the platelet surface. The expression of these receptors was measured by the agglutination of platelets to ristocetin in the presence of von Willebrand factor, which is part of the factor VIII complex, and by the binding of aggregated IgG coupled to 3H-labelled diazobenzene. Treatment of platelets with chymotrypsin, trypsin, papain and pronase which removed protein and glycoprotein from the platelet under conditions where the release reaction was inhibited caused loss of the expression of the receptor for ristocetin-von Willebrand factor and an enhancement of that for aggregated IgG. Induction of membrane changes with ADP and of the release reaction with the ionophore A23187 abolished agglutination to ristocentin-von Willebrand factor but did not alter the receptor for aggregated IgC. Possible contributions of unspecific membrane changes, produced by protease treatment of platelets, to the modification of receptor expression were eliminated by the use of formaldehyde-treated platelets. Trypsin, papain and pronase destroyed the ability of these platelets to agglutinate to ristocetin-von Willebrand factor but produced no change in the binding of aggregated IgC. Therefore, the receptor for ristocetin-von Willebrand factor is truly sensitive to proteolysis while the Fc receptor is not, but is partially masked by protease-sensitive material.

Adenosine Diphosphate↗
PubMed1977

Isolation of the membrane glycoproteins of human blood platelets by lectin affinity chromatography.

The major platelet membrane glycoproteins have been solubilized in 1.0% sodium deoxycholate and subjected to affinity chromatography on the lectins from Lens culinaris, wheat germ and Abrus precatorius. Polyacrylamide gel electrophoresis in the presence and absence of a reducing agent together with the differential binding of the lectins to the glycoproteins permitted the distinction of at least seven separate glycoprotein entities. A new nomenclature for the glycoproteins is proposed to accomodate the additional data. Using combinations of lectin columns, glycoproteins Ia and Ib could be prepared in a pure state and IIb and IIIa could be greatly purified. The binding of lectins to glycoprotein Ib has been strongly implicated as a necessary step in the aggregation response of platelets to lectins.

Blood Platelets↗
PubMed1976

Platelet membrane glycoproteins implicated in ristocetin-induced aggregation. Studies of the proteins on platelets from patients with Bernard-Soulier syndrome and von Willebrand's disease.

The antibiotic ristocetin only aggregates platelets in the presence of plasma von Willebrand factor. Platelets from patients with Bernard-Soulier syndrome do not aggregate upon addition of ristocetin although, in contrast to von Willebrand's disease, plasma levels of factor VIII complex (factor VIII clotting activity, von Willebrand factor activity, and von Willebrand antigen) are normal. The membrane surface of normal platelets was modified and compared to the surface of platelets from a patient with Bernard-Soulier syndrome in an attempt to identify the receptor involved in von Willebrand factor-ristocetin-induced aggregation. After the incubation of washed normal platelets with a preparation of ristocetin previously shown to contain a proteolytic contaminant, the aggregation response is significantly decreased on addition or normal plasma. Analaysis by gel electrophoresis of such platelets when stained for carbohydrate revealed a decrease in the relative amounts of membrane glycopro-eins. Chymotrypsin-treated normal platelets had less membrane glycoproteins in addition to giving a reduced aggregation response in ristocetin-induced aggregation. Staining of gels for protein and carbohydrate indicated that there was an extensive change in the surface of Bernard-Soulier platelets, whereas those from patients with von Willebrand's disease appeared the same as normal. Platelets from patients were labeled by the lactoperoxidase iodination technique. Not only was the relative intensity of staining of platelet-specific proteins and glycoproteins changed in Bernard-Soulier platelets, but the iodination of the glycoproteins on the membrane surface relative to other membrane constituents was lower. In contrast, platelets from patients with von Willebrand's disease showed a normal exposure of membrane components. These data suggest therefore that membrane glycoproteins may play a functional role in ristocetin-induced aggregation.

Binding Sites↗