PubMed Health⌕ Search

Biomedical subjects

M G Martin

Publications and source records attributed to M G Martin.

At least 19 recordsLinked to original sources
PubMed2005

Epitaxy and magnetic properties of surfactant-mediated growth of bcc cobalt.

High resolution core level photoemission spectroscopy, photoelectron diffraction, and x-ray magnetic circular dicroism (XMCD) have been used to characterize the structural and magnetic properties of bcc-cobalt films grown on GaAs(110) substrates by using Sb as a surfactant. We have unambiguously disentangled the surfactant role played by the Sb which improves the crystallinity and reduces the lattice distortion of the metallic films as well as changes the interdiffusion process at the interface compared to the Co/GaAs(110) system. As a consequence of these combined effects, an improvement on the magnetic response of the grown Co thin films has been observed by XMCD measurements.

Journal Article↗
PubMed2000

The effect of immunosuppression on posttransplant lymphoproliferative disease in pediatric liver transplant patients.

BACKGROUND: Posttransplant lymphoproliferative disease (PTLD) is a serious complication associated with the use of chronic immunosuppression for solid organ transplantation. This study represents a retrospective analysis of UCLA's experience with PTLD in all pediatric liver transplant recipients between 1984-1997. We assessed the clinical presentation, risk factors, incidence density, immunological characteristics, management, and outcome of patients who developed PTLD when receiving either primary cyclosporin A (CsA) or tacrolimus. METHODS: A total of 251 children received primary CsA therapy of which 70 required OKT3 for steroid resistant rejection and 29 required tacrolimus rescue for OKT3 resistance and/or chronic rejection. One hundred forty one children received tacrolimus as primary therapy. Sixty patients who survived for less than 6 months after transplantation were excluded from the study. RESULTS: The total incidence density (ID) rate of PTLD was 1.8+/-0.4 per 100 patient-years (30/392). The overall ID rate of PTLD in the CsA group was 0.93+/-0.2 per 100 patient-years (15/251). Within this group of primary CsA-treated patients, the ID rate of PTLD was 0.49+/-0.1 without OKT3 or tacrolimus, 0.67+/-0.2 with OKT3, and 6.42+/-1.1 with tacrolimus rescue. The overall PTLD ID rate in the primary tacrolimus-treated patients was 4.86+/-1.2 per 100 person-years (15/141). There was a 5-fold increase in the ID rate of PTLD in the primary tacrolimus group when compared to the comparable, primary CsA group (P<0.001). The mean time to PTLD was 5-fold longer (49.7+/-20.7 months) in the CsA group when compared to the CsA/tacrolimus rescue group (9.8+/-3 months, P<0.05) or the tacrolimus primary group (12.6+/-5.1 months, P<0.05). Five patients had monoclonal disease in the CsA group, but only one in the tacrolimus group (P<0.05). Clinical presentations with enlarged lymph nodes, fevers, malaise, anorexia, weight loss, hypoalbuminemia, and gastrointestinal blood loss were common. Mortality was 20%, three patients died in each group. CONCLUSION: The use of primary tacrolimus therapy was associated with a significant 5-fold higher rate of PTLD when compared to those treated with primary cyclosporine. Early diagnosis, decrease and/or discontinuation of potent immunosuppressive agents may contribute to decrease morbidity and mortality of this entity.

Adolescent↗
PubMed2000

Does liver transplantation affect growth pattern in Alagille syndrome?

Alagille syndrome (AGS) is frequently associated with growth failure, which has been attributed to concurrent congenital anomalies, cholestasis, and malabsorption and/or malnutrition. However, the underlying cause of the growth failure is not well understood. Our objective is to analyze the growth pattern in 26 patients with AGS and the possible effect that orthotopic liver transplantation (OLT) may have on this pattern. The standardized height, weight, and growth velocity of 26 pair-matched patients with AGS were compared. Thirteen patients underwent OLT. Repeated-measure ANOVA methods were used for the statistical analysis. The overall mean standardized height (z score) was -2.92 in the OLT group versus -1.88 in the non-OLT group (P =.03). The overall mean standardized weight was -1. 21 in the non-OLT group and -1.67 in the OLT group (P =.23). In 15 patients, birth weight was 2.82 +/- 0.4 kg, for a mean standardized weight of -0.95, and weight at diagnosis was 4.53 +/- 2.12 kg, for a mean standardized weight of -1.56. Bone age was delayed in the 9 patients who underwent bone-age analysis. Growth hormone therapy administered to 2 patients did not improve growth. Patients with AGS had growth failure secondary to other factors in addition to liver disease. Growth failure beginning in the prenatal period supports a genetic basis for this feature. Growth improvement up to normal levels should not be expected as a benefit of OLT in these patients. Growth failure as a primary indication for OLT should be cautiously examined in patients with AGS.

Age Determination by Skeleton↗
PubMed1999

The involvement of the gastrointestinal tract in posttransplant lymphoproliferative disease in pediatric liver transplantation.

BACKGROUND: Posttransplant lymphoproliferative disease (PTLD) is a serious complication associated with the use of immunosuppression after transplantation. In a retrospective study the clinical features of PTLD located primarily in the gastrointestinal tract were analyzed. METHODS: Three hundred ninety-two consecutive pediatric patients who underwent orthotopic liver transplantation (OLT) during a 13-year period with a survival of more than 6 months were reviewed. Two immunosuppression protocols were used: cyclosporin A, or tacrolimus-based primary therapy. Twenty-nine randomly selected liver transplant recipients without PTLD were used for comparison of signs and symptoms of gastrointestinal PTLD. RESULTS: Among the 30 patients identified with PTLD, 9 had gastrointestinal PTLD. The overall incidence density of PTLD was 1.8 per 100 patient-years (30/392). Nine patients (30%) had involvement of the gastrointestinal tract, whereas 7 (23%) had the gastrointestinal tract as the only involved site. When compared with a cohort of liver transplant recipients without PTLD, only gastrointestinal bleeding, weight loss, hypoalbuminemia, and protein-losing enteropathy were signs most likely associated with gastrointestinal PTLD. Hypoalbuminemia was the most sensitive sign of gastrointestinal PTLD. The lower tract (ileum and colon) was the most common site of involvement. CONCLUSIONS: gastrointestinal involvement is common and occurs in 30% of all patients with PTLD. It may be the only affected organ in a subgroup of patients. Hypoalbuminemia, gastrointestinal bleeding, and weight loss are features that are characteristic of gastrointestinal PTLD. Patients with aggressive gastrointestinal signs and symptoms should undergo upper and lower gastrointestinal tract endoscopy with biopsy, to establish the diagnosis.

Adolescent↗
PubMed1999

Variable morbidity in alagille syndrome: a review of 43 cases.

BACKGROUND: Alagille syndrome is one of the most common inherited disorders that cause chronic liver disease in children. Early reports suggested a benign course in these patients. Subsequent reports showed significant morbidity and mortality. This study was designed to analyze the long-term clinical course in Alagille syndrome. METHODS: The records of children with Alagille syndrome seen during a 20-year period were reviewed. RESULTS: Forty-three patients were identified. Liver disease was diagnosed before 12 months of age in 95%. The frequencies of renal anomalies (50%) and intracranial hemorrhage (12%) were significant. The high incidence of chronic otitis media (35%) has not been reported previously. One patient had a renal transplant. Vascular compromise as a pathologic mechanism for some characteristics of the syndrome is also suggested by the presence of small bowel stenosis and atresia, tracheal and bronchial stenosis, renal artery stenosis, middle aortic syndrome, and avascular necrosis of the humeral and femoral heads. Twenty (47%) patients underwent liver transplantation. Five of six who underwent Kasai procedure required liver transplantation. Twelve died (28%), five after liver transplantation. One patient died of intracranial bleeding. Sixteen (37%) without liver transplantation and 15 (35%) who underwent liver transplantation are alive. CONCLUSIONS: Some patients with early-onset and more severe liver disease can benefit from liver transplantation. Careful and complete assessment should be made of infants with a cholestatic syndrome, to avoid misdiagnosis and unnecessary Kasai procedures. Our observation of vascular compromise in various organ systems suggests that notch signaling pathway defects affect angiogenesis in Alagille syndrome.

Adolescent↗
PubMed1998

De novo hepatitis C in children after liver transplantation.

BACKGROUND: We describe the incidence, results of interferon therapy, and outcome of hepatitis C virus (HCV) hepatitis occurring de novo after pediatric orthotopic liver transplantation (OLT). METHODS AND RESULTS: Of children undergoing OLT between 1984 and September 1996, 321 children survived for more than 1 year. Of these, 13 (4.0%) developed previously undiagnosed HCV disease, as suggested by HCV antibody testing and HCV polymerase chain reaction and confirmed by liver biopsy. Of the 117 children who received transplants before HCV screening of blood products or donors, 10.2% developed de novo HCV disease. The mean age at diagnosis of HCV hepatitis was 13.2+/-5.0 years, and the mean time to diagnosis after OLT was 8.1 years (range, 4-11 years). The mean alanine aminotransferase (ALT) level at diagnosis was 108 IU/ml, and the liver biopsy specimen showed chronic active or chronic persistent hepatitis in 11 children, cirrhosis in 1 child, and nonspecific changes in 1 child. Twelve children were treated with interferon-2alpha; children who weighed > or =20 kg received 3 x 10(6) units every other day, and those who weighed <20 kg received 1.5 x 10(6) units every other day. Four patients developed rapidly progressive liver failure while receiving interferon therapy and required urgent re-transplantation. Three of the four children again developed histologic evidence of recurrent HCV 4-6 months after the second OLT, and all three subsequently died of HCV-induced liver failure. One patient remains alive and well with no evidence of HCV recurrence and a negative HCV RNA. Of the remaining eight children treated with interferon, only two have had a sustained response (normal ALT) and one is now HCV RNA negative. HCV RNA levels did not correlate with outcome or disease severity. HCV antibody levels were unreliable, with two patients having negative HCV antibody but a positive HCV RNA at diagnosis. Six patients were able to be genotyped: four were la and two were 1b. CONCLUSION: Overall mortality for de novo HCV hepatitis was 23%. Seventy-five percent of children who received a second transplant for HCV hepatitis had early histologic recurrence that led to liver failure and death. Interferon therapy resulted in a sustained improvement in ALT in only 15% of children. The time to onset and progression of clinical disease both in the original graft and the retransplant graft were accelerated compared with nonimmunosuppressed individuals.

Adolescent↗
PubMed1998

Triggering of the lesser toes at a previously undescribed distal pulley system.

We have treated five patients with metatarsalgia and triggering of the lesser toes. This paper describes a mechanism of triggering that involves a previously undescribed flexor pulley system in the toes that is very similar to the pulley system in the fingers. The specific anatomy of the toe flexor pulleys is described based upon the dissections of 50 fresh-frozen cadaver toes. These pulleys were composed of transverse to obliquely oriented fibrous bands within the flexor sheaths from the metatarsal heads to the distal phalanges. We found a system of pulleys in the lesser toes and the great toe, analogous to that found in the hand. Trigger toe is a rare entity and is only briefly described in the literature. We believe it is more common than is now recognized and may be an important underdiagnosed cause of metatarsalgia. The diagnosis is made when active plantarflexion causes the toes to catch in flexion and the patient is then unable to extend them. Nonsurgical therapy consisting of steroid injection, NSAIDs, or changing footwear may be effective, otherwise surgical release of the A1 pulley may be required.

Adult↗
PubMed1995

Effect of follicular components on meiotic arrest and resumption in horse oocytes.

Two experiments were conducted to evaluate the effect of follicular components on the maintenance of meiotic arrest in horse oocytes. In Expt 1, oocytes were incubated for 24 h with follicular fluid, or with granulosa cells suspended either in medium or in follicular fluid at 25 x 10(6) cells ml-1. None of the treatments resulted in significant maintenance of the germinal vesicle stage over that of non-suppressive control. Culture with follicular fluid plus granulosa cells resulted in a significantly higher proportion of oocytes at metaphase I compared with controls. In Expt 2, oocytes were divided into those originally having compact or expanded cumuli. Oocytes were cultured with sheets of mural granulosa or sections of follicle wall, or after injection into intact dissected follicles. After incubation, half of the oocytes from each suppressive treatment were matured for 24 h. All three suppressive treatments were effective in maintaining oocytes at the germinal vesicle stage (no significant difference from control oocytes fixed directly after removal from the follicle). However, no treatment maintained normal viability of oocytes, as significantly fewer oocytes were at metaphase II after all the suppression-maturation treatments compared with the maturation control. The highest rate of post-suppression maturation was found in the mural granulosa treatment. Within this treatment, the proportion of oocytes in metaphase II was significantly higher for oocytes with expanded than for oocytes with compact cumuli (31% versus 11%, respectively; P < 0.05). Suppression by injection into an intact follicle was associated with a lack of progression to metaphase II during subsequent maturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

In vitro maturation of horse oocytes: characterization of chromatin configuration using fluorescence microscopy.

The chromatin configuration of resting horse oocytes and the time course of in vitro oocyte maturation was characterized using a fluorescent, DNA-specific label. Oocytes were classified as having either compact (CP) or expanded (EX) cumuli at the time of collection. Centrifugation of oocytes was effective in allowing visualization of the germinal vesicle. Two main chromatin configurations were found in oocytes known to have a germinal vesicle: condensed chromatin (CC), in which the chromatin formed a dense mass surrounding the nucleolus; and fluorescing nucleus (FN), in which the entire nucleus, containing diffuse or spotty chromatin, was visible. The proportion of CC to FN was higher for oocytes with EX cumuli. At time 0, 78% of CP oocytes and 73% of EX oocytes were in the germinal vesicle stage. Significantly more EX than CP oocytes were in metaphase I or II at time 0. In both CP and EX groups, maturation had not begun after 8 h of incubation. Maximal maturation occurred after 24 h for oocytes in the EX group, whereas CP oocytes continued to mature between 24 and 32 h. The percentage of EX oocytes in metaphase I did not change between 24 and 32 h, indicating a possible arrest of some EX oocytes at metaphase I. There was no difference in the percentage of oocytes at metaphase II between the CP and EX groups after 32 h of incubation.

Animals↗
PubMed1992

Autonomous proliferation of colon cancer cells that coexpress transforming growth factor alpha and its receptor. Variable effects of receptor-blocking antibody.

Four human colon adenocarcinoma cell lines, SNU-C1, SNU-C4, SNU-C5, and NCI-H716, that are capable of proliferating autonomously in serum-free medium containing no added peptide growth factors were identified. All four cell lines show epidermal growth factor (EGF) receptors (EGFRs), express transforming growth factor alpha (TGF-alpha) messenger RNA, and release anti-TGF-alpha-immunoreactive molecules. The blocking anti-EGFR monoclonal antibody (mAb) 225 blocks autonomous proliferation of SNU-C1 and SNU-C4 cells. In both of these cell lines, the inhibitory effect of mAb 225 is reversible by the addition of EGF, TGF-alpha, or conditioned medium from any of the four cell lines. In contrast, autonomous proliferation of SNU-C5 and NCI-H716 cells is not inhibited by mAb 225 and is not affected by exogenous EGF, TGF-alpha, or conditioned medium. Together, these data confirm the previous finding that anti-EGFR antibodies can inhibit the proliferation of some carcinoma cell lines that coexpress TGF-alpha and EGFR. However, here it is shown that the mechanisms of autonomous proliferation of colon carcinoma cell lines are heterogeneous and not always sensitive to antibody disruption of TGF-alpha/EGFR autocrine interactions.

Adenocarcinoma↗
PubMed1989

Development of calcium channels in gastric smooth muscle.

We used [3H]nitrendipine to characterize dihydropyridine sensitive calcium channels on cells isolated from neonatal (1 d) and weanling (11 wk) rabbit gastric fundic and antral smooth muscle. Incubating with and without nifedipine 20 microM, specific binding was 56 +/- 4% of total binding at 0.1 nM [3H]nitrendipine. Specific binding was saturable, reversible, achieved equilibrium by 10 min at 4 degrees C, and was linearly related to cell concentration. The affinity constant for [3H]nitrendipine was higher in weanling fundus (kd = 243 +/- 121 pM) versus antrum (kd = 771 +/- 190 pM), p less than 0.05. There were no age-related changes in affinity. In the antrum, the number of binding sites (Bmax) increased from 6,000 +/- 266/cell in neonates to 27,500 +/- 8,440/cell in weanlings (p less than 0.05). In the fundus Bmax was 7,750 +/- 2,100/cell in neonates, and there was no age-related change. To assess function, we compared isometric stress in full thickness muscle strips oriented to the circular layer. Bethanechol stimulated dose-dependent tonic contractions in the fundus and phasic contractions in the antrum. Maximal stress increased with age from 305 +/- 54 mN/cm2 to 1140 +/- 73 mN/cm2 (p less than 0.05) in the fundus and from 72 +/- 20 mN/cm2 to 154 +/- 30 mN/cm2 (p less than 0.05) in the antrum. Preincubation and incubation without calcium resulted in reversible inhibition of contraction at both ages. Nifedipine 10-microM inhibited 100% of bethanechol-stimulated contraction in the antrum, but only 25% in the fundus at both ages.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1977

Fluorescence urinary cytology in bladder cancer.

300 patients have been studied by means of a fluorescence exfoliative urinary cytology procedure based on the fluorochromatic properties and the affinity of acridine orange for the nucleic acids. The patients were divided inot two groups: in the first group including 238 cases we tried to establish the correlation between the urinary cytological grade and the histological grade of malignancy on biopsy; the rate of accuracy was approximately 77% for low-grade and approximately 88% for the high-grade tumours. In the second group including 62 cases we studied the value of cytology in predicting recurrences; 38 and 66.6% of the cases with grades IV and V, respectively, developed recurrences thus confirming the necessity of cytologic controls in patients under conservative treatment. The overall rate of accurate cytological diagnosis with this staining method has reached 90%.

Cytodiagnosis↗
PubMed1975

Poisoning and poison control centres in Canada.

Poisoning is a major and increasing health problem in the Western world. In 1972 the 310 poison control centres in Canada reported 53 531 enquiries about poisoning, 40% in adults. In 1964 the numbers of hospital admissions and deaths due to poisoning in this country were 2446 and 38, respectively, but in 1972 the figures were 6263 and 319, respectively. Most of the hospitalizations and deaths were among adults. Of 100 Canadian poison control centres two thirds were staffed by "any nurse in the emergency room", most of whom had received no training to answer the phone enquiries. However, two thirds agreed a training program is needed. Only 6.7% of 223 parents surveyed stated they would call a poison control centre if their child had accidentally swallowed a large amount of a poisonous substance. Regionalization of centres, a training program for personnel answering telephone enquiries, the need for crisis intervention as part of poison control programs, and public education about poisoning and poison control centres are the new challenges facing those providing health services.

Canada↗
PubMed1975

Extracorporeal repair of the renal artery for renovascular hypertension: a case report.

A case of successful correction of renovascular hypertension by means of extracorporeal repair of fibroplasia of the main trunk and an aneurysm of a secondary division branch of the left renal artery is presented. The ureter was not transected and a segment of the internal ilac artery with two branches was used for the substitution of the diseased renal artery segments. The kidney was preserved by intermittent flushing with iced Ringer's lactate solution. A probable post-operative arterial thrombosis of the repaired secondary branch was successfully treated with intravenous streptokinase. One year after the operation the patient is normotensive.

Adult↗