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Biomedical subjects

D Smith

Publications and source records attributed to D Smith.

At least 451 records · Page 25Linked to original sources
PubMed1997

Resistance to chemotherapeutic antimetabolites: a function of salvage pathway involvement and cellular response to DNA damage.

The inherent or acquired (induced) resistance of certain tumours to cytotoxic drug therapy is a major clinical problem. There are many categories of cytotoxic agent: the antimetabolites, e.g. methotrexate (MTX), N-phosphonacetyl-L-aspartate (PALA), 5-fluorouracil (5-FU), 6-mercaptopurine (6-TG), hydroxyurea (HU) and 1-beta-D-arabinofuranosylcytosine (AraC); the alkylating agents, e.g. the nitrogen mustards and nitrosoureas; the antibiotics, e.g. doxorubicin and mitomycin C; the plant alkaloids, e.g. vincristine and vinblastine; and miscellaneous compounds, such as cisplatin. There are also many mechanisms of drug resistance elucidated principally from in vitro studies. These include mutation of target genes, amplification of target and mutated genes, differences in repair capacity, altered drug transport and differences in nucleoside and nucleobase salvage pathways (Fox et al, 1991). The aim of the present review is to evaluate in detail the mechanisms of response of both normal and tumour cells to three chemotherapeutic antimetabolites, MTX, PALA and 5-FU, which are routinely used in the clinic either alone or in combination to treat some of the commonest solid tumours, e.g. breast, colon, gastric and head and neck. The normal and tumour cell response to these agents will be discussed in relation to the operation of the known alternative 'salvage pathways' of DNA synthesis and current theories of DNA damage response.

Animals↗
PubMed1997

Phagocytic degradation of chylomicron remnants by fibroblasts from subjects with homozygous familial hypercholesterolaemia.

1. Familial hypercholesterolaemia is a common genetic abnormality in man characterized by premature atherogenesis as a consequence of disturbed lipoprotein metabolism. Chylomicrons, which represent intestinally derived lipoproteins, are cleared poorly in familial hypercholesterolaemia which may explain the increased retention of chylomicron remnants in arterial fatty lesions. However, cellular uptake of chylomicron remnants in familial hypercholesterolaemia remains unclear. This study determined the quantitative significance of non-low-density lipoprotein receptor-mediated uptake in fibroblasts from subjects with homozygous familial hypercholesterolaemia. 2. The metabolism of chylomicron remnants was assessed in fibroblasts from subjects with homozygous familial hypercholesterolaemia who lack low-density lipoprotein receptors. Compared with fibroblasts from normolipidaemic subjects, binding and degradation of chylomicron remnants was reduced by about two-thirds. Nevertheless, degradation of chylomicron remnants in cells from subjects with familial hypercholesterolaemia persisted in the absence of functioning low-density lipoprotein receptors. 3. Binding of chylomicron remnants to fibroblasts from subjects with familial hypercholesterolaemia was saturable. Unlabelled chylomicron remnants competed efficiently for binding but unlabelled low-density lipoprotein or a monoclonal antibody specific to the human low-density lipoprotein receptor had little effect on binding or degradation. 4. Polyinosinic acid did not alter binding and degradation of chylomicron remnants by fibroblasts from subjects with familial hypercholesterolaemia, ruling out involvement of the scavenger receptor. Lactoferrin was found to inhibit binding and degradation of chylomicron remnants by fibroblasts from subjects with familial hypercholesterolaemia by approximately 50%, implicating involvement of the alpha 2-macroglobulin receptor. 5. Cytochalasin D blocked degradation of chylomicron remnants at 37 degrees C in fibroblasts from subjects with familial hypercholesterolaemia by more than 80% but had no effect on binding at 4 degrees C, consistent with a phagocytic uptake pathway. Collectively, the data suggest that chylomicron remnants bind to a cell-surface protein which initiates phagocytosis and that lactoferrin interferes with binding to this putative cell-surface protein. Phagocytic uptake of chylomicron remnants provides an additional mechanism whereby cells from subjects with familial hypercholesterolaemia can accumulate lipid.

Adult↗
PubMed1997

T-cell-independent granuloma formation in response to Mycobacterium avium: role of tumour necrosis factor-alpha and interferon-gamma.

We used Mycobacterium avium infection in severe combined immunodeficiency (SCID) mice to examine T-cell-independent mechanisms of inflammatory cell recruitment. SCID mice infected with a virulent strain of M. avium (TMC724) were able to recruit macrophages to sites of mycobacterial replication and formed organized and coherent granulomas in the absence of functional T cells. Phagocyte recruitment was almost totally ablated by neutralization of either tumour necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma) in vivo demonstrating that granuloma formation was dependent on the presence of these cytokines. This was concomitant with a reduction in the in situ cytokine mRNA levels otherwise induced in infected mice, for chemokines, pro-inflammatory and regulatory cytokines, including TNF-alpha, IFN-gamma, macrophage inflammatory protein-1 alpha, interleukin-1 beta (IL-1 beta) and IL-10. Furthermore, in vivo treatment of infected mice with anti-asialo GM-1 antisera, which depletes natural killer (NK) cells, prevented recruitment of inflammatory cells. In vitro studies confirmed that M. avium was able to elicit IFN-gamma from SCID spleen in a dose-dependent manner. These data show for the first time that secretion of IFN-gamma from NK cells can mediate a T-cell-independent pathway of granuloma formation and cellular infiltration in response to mycobacteria.

Animals↗
PubMed1997

First clinical experiences with specific sheep Fab fragments in snake bite. Report of a multicentre study of Vipera berus envenoming.

OBJECTIVES: To evaluate the efficacy and safety of specific, ovine Fab fragments in the treatment of envenoming by the common adder, Vipera berus. DESIGN: Open study with historical controls. SETTING: Multicentre study involving patients (n = 30) with V. berus envenoming, treated in 18 Swedish hospitals during 1991-94. MAIN OUTCOME MEASURES: Initial symptoms, clinical course after treatment, duration of hospital stay and adverse effects of the antivenom were evaluated. Two earlier studied patient groups, given either equine F(ab)2 antivenom (n = 30) or no antivenom (n = 16), were used as controls. RESULTS: Specific ovine Fab fragments influenced favourably the acute symptomatology as well as the long term clinical course. Acute symptoms such as hypotension, shock, vomiting, diarrhoea and CNS-depression resolved quickly. The incidence of extensive swelling involving the trunk and the length of hospital stay were both reduced significantly compared to nontreated patients (23 vs. 88% and 3.5 vs. 6 days). Also the incidence of anaemia was reduced (23 vs. 44%). These results were consistent with those obtained with equine F(ab')2 antivenom, but with ovine Fab there were no immediate anaphylactic reactions or serum sickness. CONCLUSION: Specific Fab fragments produced from sheep immunized with V. berus venom were safe and effective in counteracting the effects of V. berus bite in humans. These results justify further studies of this new treatment for snake envenoming.

Adolescent↗
PubMed1997

Differential distribution of 5HT1D- and 5HT1B-immunoreactivity within the human trigemino-cerebrovascular system: implications for the discovery of new antimigraine drugs.

Sumatriptan, a 5HT1B/1D-receptor agonist, is clinically effective as an antimigraine agent. Its therapeutic action may result partly from vasoconstriction of excessively dilated cranial blood vessels (a 5HT1B-receptor mediated response). The antimigraine activity of sumatriptan may also result from inhibition of the release of vasoactive neuropeptides from trigeminal sensory fibres within the meninges. The identity of the 5HT1B/1D-receptor subtype mediating this effect is unknown. Using 5HT1D- and 5HT1B-receptor-specific antibodies we have demonstrated a differential distribution of these receptor subtypes within the human trigemino-cerebrovascular system. Only 5HT1B-receptor protein was detected on dural arteries. In contrast, only 5HT1D-receptor protein was detected on trigeminal sensory neurones including peripheral and central projections to dural blood vessels and to the medulla. Within the medulla 5HT1D-receptor protein was confined to discrete areas associated with the trigeminal sensory system. These findings have important implications for the design of new antimigraine drugs.

Adult↗
PubMed1997

Effect of vitamin E supplementation on prostaglandin concentrations in aspirin-induced acute gastric injury in aged rats.

Nonsteroidal antiinflammatory drugs (NSAIDs), such as aspirin, frequently cause gastric mucosal injury in the elderly. Impairment of prostaglandin synthesis is a crucial step by which aspirin attenuates mucosal defense capacity. Vitamin E has been shown to decrease prostanoid concentrations, which implies an ulceropermissive effect of vitamin E. To assess the effect of vitamin E on aspirin-induced gastric injury and mucosal prostanoid concentrations, 20 male rats aged 20 mo were divided into two groups and fed diets containing either 30 (physiologic requirement) or 500 mg all-rac-alpha-tocopheryl acetate/kg. After 6 wk, all rats received two intragastric doses of aspirin (1.4 mumol/kg body wt). A third group of six animals fed the high-vitamin E diet received a vehicle solution without aspirin. Mucosal samples for vitamin E and prostaglandin E2, 6-keto-prostaglandin F1 alpha, and thromboxane A2 measurements were collected. The prevalence and degree of mucosal lesions were not significantly different among all groups. Rats fed the high-vitamin E diet had significantly higher mucosal vitamin E concentrations than rats fed the low-vitamin E diet. Mucosal concentrations of all three prostanoids were 95% lower in aspirin-treated rats than in controls (P = 0.0001 in all instances). The high-vitamin E diet group had significantly lower mucosal 6-keto-prostaglandin F1 alpha concentrations (P = 0.02) than the low-vitamin E diet group, indicating decreased prostacyclin formation, whereas concentrations of prostaglandin E2 and thromboxane A2 were similar in the aspirin-treated groups. Aspirin markedly reduced mucosal prostanoid concentrations in rats, without apparent effects on gastric injury, whereas vitamin E supplementation significantly reduced mucosal 6-keto-prostaglandin F(1 alpha) concentrations. Nevertheless, vitamin E supplementation did not result in more gastric injury in aspirin-treated rats than in controls.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

An outcome analysis of 100 women after explantation of silicone gel breast implants.

A prospective outcome analysis was conducted on 100 consecutive women who requested explantation of their silicone gel breast implants from January 6, 1992 (the moratorium), through 1995. Eighteen patients were referred by rheumatologists with a diagnosis of autoimmune or rheumatic disease. Six had autoimmune disease (systemic lupus, 2 patients; rheumatoid arthritis, 2 patients; multiple sclerosis, 1 patient; and Raynaud's disease, 1 patient). Twelve had rheumatic disease (fibromyalgia, 10 patients; inflammatory arthritis, 2 patients). All of these 18 patients had developed symptoms of their disease after they had received implants. All 100 patients were extensively evaluated pre- and postoperatively by interviews, clinical assessment, and by assay of the following laboratory tests: rheumatoid factor, ESR, ANA, and anti-Ro/SSA, -La/SSP, -Sm, -RNP, -double-stranded deoxyribonucleic acid, -Scl-70, -centromere, and -cardiolipin. Patients were also evaluated by a questionnaire that was sent at a mean time of 2.7 years postexplantation (range, 1-5 years), which had a 75% response rate. Reasons for implants were augmentation, 75%; lifting, 11%; reconstruction, 12%; and congenital aplasia, 2%. The mean age at first implant was 28.9 years (range, 13-55 years) and at explantation was 41.5 years (range, 25-65 years). The mean duration of implantation was 12.0 years (range, 1-27 years). Thirty-six percent of the patients had undergone at least one closed capsulotomy and 54% at least one open capsulotomy. The mean reasons for explantation were suspected silicone-related health problems, 76%; suspected rupture, 59%; breast firmness, 36%; breast pain, 36%; and musculoskeletal pain, 23%. Before explantation 75% of the questionnaire respondees had lost some sensitivity in their nipples following their breast augmentation. In 36% of those 75 patients, that loss was almost complete. Loss of sensitivity was related to capsular contracture and to pain (p < 0.05). Following explantation there was significant improvement in nipple sensitivity in 38% of breasts in the 75 respondees. A total of 186 implants were removed. Fifty-seven percent had failed by rupturing or leaking. Only 3.2% demonstrated extravasation extracapsularly. Twenty-five percent of the capsules were calcified, demonstrating visible plaques of calcification on their inner surface. Forty-two percent were colonized by bacteria. The prevalence of class III-IV capsular contracture was 61% and it was related to implant location, duration in situ, and capsular calcification (p < 0.05), but not to capsular colonization or implant integrity (p > 0.05). Only 43 of the 100 patients elected to have saline implants inserted. Of the others, 56% felt that the shell of the saline implant could be associated with medical problems. The others felt that breast size was of minor importance to them at this time. There were few complications from the explantation procedure. Two "masses" were discovered-one was an occult carcinoma, the other a galactocele. There was one wound infection, which responded to antibiotics. Three patients developed decreased sensitivity and 3 developed increased breast pain. From the patient questionnaires, in those women who did not have saline implants inserted, 15% felt that their breast appearance was improved after explantation, 36% were "pleased," 33% were disappointed, and 13% felt "mutilated". In women who did have saline implants inserted, 18% felt that their breast appearance was now improved, 60% were "pleased," and 14% were disappointed, mainly because of wrinkling. At a mean time of 2.7 years (range, 1-5 years) after explantation, 45% of the 75 questionnaire respondees felt that their implants had caused permanent health problems and 56% felt that they had not been given adequate informed consent by their original surgeon (particularly regarding implant rupture and a possible relationship to medical disease). (ABSTRACT TRUNCATED)

Adolescent↗
PubMed1997

Motor complications of chronic levodopa therapy in Parkinson's disease.

We report on motor complications of chronic levodopa therapy among 811 levodopa-responsive patients with idiopathic Parkinson's disease (PD), stratified by duration after diagnosis. Predictable "offs" were noted in 20.2% of patients in the first 5 years, in 58.3% after 15 years. Unpredictable or sudden offs and early morning dystonia were less common. Longer duration was associated with greater percentages of patients with off periods or dyskinesias (up to 70% after 15 years), although patients with 6-15 years' duration saw relatively little increase in frequency of those complications, and a minority of patients (approximately 30%) with duration into the second decade did not experience off periods or dyskinesia. Across groups, mean Hoehn and Yahr stage and daily levodopa dosage progressively increase (and mean Schwab and England disability ratings decrease), but more conservatively than in prior reports in the postlevodopa era. We note that with advancing PD duration, levodopa complications are more common, but in many cases there appear to be relatively stable periods in terms of levodopa dosage and disease severity, and a minority of patients will be relatively free of motor complications into the second decade of their disease.

Adult↗
PubMed1997

Binding of malignant lymphoid cells to the white matter of the human central nervous system: role of different CD44 isoforms, beta 1, beta 2 and beta 7 integrins, and L-selectin.

Spreading of reactive and malignant lymphoid cells into the brain parenchyma requires regulated adhesion of the lymphoid cells to the parenchymal cells and/or extracellular matrix of the central nervous system. A multifunctional adhesion molecule CD44 partially mediates binding of lymphocytes to the white matter by interacting with hyaluronate. To analyze which forms of CD44 and what other adhesion molecules mediate this binding. Namalwa cells were transfected to express either standard (CD44st) or variant isoforms of CD44 containing exons v6-v10, v7-v10, and v8-v10. The binding of CD44st and CD44v6-v10 transfectants to human cerebellar white matter was tested and it was about 1.7- and 2-fold greater without and with PMA activation, respectively, compared with vector-transfected control cells. Hyaluronidase digestion of tissue sections decreased binding of CD44 expressing cells to the level of vector-transfected cells. Hermes-1, a monoclonal antibody recognizing the hyaluronate binding site of CD44, inhibited white matter adhesion of CD44v6-v10 and activated CD44st cells and binding of soluble hyaluronate to the CD44 transfectants. Transfectants also expressed beta 1, beta 2 and beta 7 integrins and L-selectin, but antibodies against these molecules did not inhibit adhesion to the white matter. These results suggest: (a) Addition of exons v6-v10 to the membrane proximal region of CD44 does not affect lymphoid cell adhesion to the white matter. (b) The only ligand of CD44 in the central nervous system (CNS) white matter is hyaluronate. (c) Additional adhesion mechanisms other than the ones analyzed above must exist.

Burkitt Lymphoma↗
PubMed1997

Fertility awareness in women attending a fertility clinic.

Eighty women attending for consultation at a tertiary referral fertility unit over a 3-month period were surveyed for their knowledge of fertility awareness and how they used this information to enhance their chances of conception. It was hypothesized that less than 50% of the subjects had an adequate understanding of when the fertile time occurred in their menstrual cycle. A questionnaire was completed anonymously by each subject and these were scored in 3 categories for fertility awareness by 2 independent Natural Family Planning teachers. Scores ranged from 0 for women who had no concept of fertility awareness, to 6 for women who were highly aware. The results showed that 26% (N = 21) of subjects had a score of 4 or greater which was considered as having an adequate understanding. The hypothesis was accepted, giving reason for concern about the effectiveness of consumer education at all levels of fertility investigation.

Adult↗
PubMed1997

Detection of group B rotaviruses in fecal samples from diarrheic calves and adult cows and characterization of their VP7 genes.

Groups A, B, and C rotaviruses have been identified in cattle. Group B rotaviruses are associated with sporadic cases of diarrhea in calves and adult cows. From diagnostic submissions to our laboratory, 90 fecal samples from cases of calf diarrhea, 81 fecal samples from cases of adult cow diarrhea (winter dysentery), and 20 fecal samples from case control normal adult cows were tested for group B rotaviruses by polyacrylamide gel electrophoresis (PAGE), and reverse transcription (RT)-PCR (targeting 279 bp of the VP7 gene). In addition, 53 fecal samples from diarrheic adult cows were tested for group B rotaviruses by immune electron microscopy (IEM). By RT-PCR, five samples from calves were group B rotavirus positive (5.6%). Fifteen samples from adult cows with diarrhea were group B rotavirus positive (18.5%), and none of the control fecal samples from normal cows were positive for group B rotaviruses. By PAGE, one calf sample (RT-PCR positive) was group B rotavirus positive (short electropherotype), but none of the adult cow samples were positive for group B rotaviruses. By IEM, 5 (9.4%) of the 53 fecal samples from diarrheic adult cows were group B positive (all were also RT-PCR positive). The VP7 genes of three strains (WD653 from an adult cow and the ATI and Mebus calf strains) were sequenced. The VP7 genes from the three bovine strains showed high (over 90%) nucleotide and deduced amino acid homologies, but lower homologies (48 to 61%) were seen between these genes and the genes from rodent (IDIR) and human (ADRV) group B rotaviruses. Although there were some differences of degree, all inoculated gnotobiotic calves (n = 6) showed abnormal feces between 1 and 3 days after inoculation with each of three strains of group B bovine rotaviruses, and group B rotaviruse, were detected in the feces for up to 2 weeks by RT-PCR but for shorter periods by PAGE or IEM.

Animals↗
PubMed1997

Dilated duct pattern at mammography.

PURPOSE: To determine the importance of a dilated duct pattern at mammography. MATERIALS AND METHODS: Mammograms obtained in 46 women with histopathologically proved, asymmetrically dilated ducts were retrospectively studied. The laterality and location of the asymmetrically dilated duct, the presence of branching, and associated findings such as microcalcifications, nipple discharge, and interval change were evaluated. RESULTS: Eleven patients (24%) had malignant results (ductal carcinoma in situ or invasive ductal carcinoma). Among these, six (54%) had suspicious microcalcifications. Nonsubareolar location and interval change are significant (P = .04) variables associated with malignancy. CONCLUSION: Mammographic asymmetrically dilated ducts in a nonsubareolar area that are associated with interval change, suspicious microcalcifications, or both warrant biopsy.

Adult↗
PubMed1997

A highly sensitive assay for quantitation of apolipoprotein B48 using an antibody to human apolipoprotein B and enhanced chemiluminescence.

We describe a method for the rapid quantification of serum apolipoprotein B48 using a commercially available anti-apolipoprotein (apo)B antiserum and compare it to analytical sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) with coomassie blue R250 staining. The method described here eliminates the need for de-lipidation of samples and only requires a one-step overnight ultracentrifugation. Western-blotting and enhanced chemiluminescence (ECL) visualization of proteins was approximately 10 times more sensitive than coomassie staining and generally took no longer to complete than staining/destaining of SDS-PAGE gels. The sensitivity of the antiserum/ECL technique enabled quantitation of fasting apolipoprotein B48 which could not be resolved by SDS-PAGE and Coomassie staining.

Apolipoprotein B-48↗
PubMed1997

Treatment of advanced breast cancer with sterically stabilized liposomal doxorubicin: results of a multicenter phase II trial.

PURPOSE: A multicenter phase II study to determine the activity and toxicity of Caelyx (Doxil; Sequus Pharmaceuticals Inc, Menlo Park, CA) in patients with metastatic breast cancer. PATIENTS AND METHODS: Seventy-one patients with stage IV breast cancer were treated with Caelyx at doses of 45 to 60 mg/m2 every 3 to 4 weeks for a maximum of six cycles. Twenty-eight patients had received prior chemotherapy with a nonanthracycline regimen. Fifty-two patients had disease at multiple sites. Hepatic and pulmonary disease were the predominant metastatic site in 50 patients. Response was assessable in 64 cases. RESULTS: Sixteen patients achieved a partial response and a complete response (overall response rate, 31%; (95% confidence interval, 20% to 43%). Twenty patients (31%) had stable disease on treatment. Neutropenia > or = grade 3 occurred in 10% of cycles (27% of patients) and mucositis > or = grade 3 in 10% of cycles (32% of patients). Significant alopecia was rare and routine prophylactic antiemetics were not required. At doses of 60 mg/m2 every 3 weeks, seven of 13 patients had > or = grade 3 skin toxicity; overall, this toxicity complicated 25% of treatment cycles. The incidence of > or = grade 3 skin toxicity was greatly reduced at doses of 45 mg/m2 every 4 weeks, occurring in five of 32 patients and affecting only 5% of 126 treatment cycles. CONCLUSION: Caelyx is an active agent in advanced breast cancer with a safety profile that differs markedly from nonliposomal doxorubicin. A regimen of 45 mg/m2 every 4 weeks was well tolerated in this cohort of women with advanced poor-prognosis breast cancer. The mild myelosuppression seen with this regimen would favor its use in combination chemotherapy.

Antibiotics, Antineoplastic↗