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Biomedical subjects

M Martinez

Publications and source records attributed to M Martinez.

At least 253 records · Page 14Linked to original sources
PubMed1992

Isolation of a fibrinolytic protease, M4, from venom of Crotalus molossus molossus (northern blacktail rattlesnake).

M4, a fibrinolytic protease, was isolated from the venom of Crotalus molossus molossus. It has a pI of 9.6 and a molecular weight of 27,000. The protease hydrolyzes the A alpha and B beta chains of fibrinogen, and the alpha and beta chains of fibrin. This activity was inhibited by EDTA and restored by Ca2+ or Zn2+, but not Mg2+. The protease hydrolyzed hide power azure and casein, but it had no effect on collagen, hyaluronic acid, complement or synthetic substrates for thrombin, plasmin or kallikrein. Subcutaneous injections into mice with doses as high as 100 micrograms did not cause hemorrhage. This protease may have therapeutic use as a thrombolytic agent.

Amino Acid Sequence↗
PubMed1992

A systematic search for a bipolar predisposing locus on chromosome 5.

Chromosome 5 markers spanning the pter to the qter were used to examine linkage to bipolar illness in 14 pedigrees. Twenty-four loci were examined in 237 individuals, of whom 69 were either bipolars or schizoaffectives. Marker genotypes were determined for each individual and lod scores were calculated under a dominant disease model with a maximum penetrance of 85%, a disease gene frequency of 0.015, a variable age of onset, and a phenocopy rate of 0.001. Under the assumption that bipolar illness is genetically homogeneous, the total lod scores from all pedigrees with each marker were uniformly lower than -2.0, suggesting the absence of linkage to disease at any of these loci. Multipoint analysis allowed exclusion of intervals between markers. When lod scores were calculated allowing for heterogeneity, no subset of linked families was found. These results indicate that in our pedigree series almost the entire mapped region of chromosome 5 can be excluded for linkage to bipolar illness.

Bipolar Disorder↗
PubMed1991

Mono(ADP-ribosyl)ation of poly(ADP-ribose)polymerase by cholera toxin.

Poly(ADP-ribose)polymerase (PADPRP) was found to be an efficient protein acceptor for the arginine-specific ADP-ribosylation reaction catalyzed by cholera toxin (CT). The covalent modification of PADPRP was carried out with [32P]2'-dNAD as a selective mono(ADP-ribosyl)ation substrate. Mono(2'-dADP-ribosyl)ated-PADPRP was identified by autoradiographic analysis of the CT reaction products following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Addition of recombinant ADP-ribosylation factor (rARF), a small GTP-binding protein that stimulates the enzymatic activity of CT, enhanced the mono(2'-dADP-ribosyl)ation of PADPRP in a time- and substrate-dependent manner. In contrast, rARF did not change the ADP-ribose polymerizing activity of PADPRP. Peptide mapping mapping of [32P] labeled (2'-dADP-ribose)-PADPRP, following partial proteolysis with papain, revealed that the DNA-binding domain of PADPRP contained the mono(2'-dADP-ribosyl)ated arginine residue(s). Our results are consistent with the conclusion that PADPRP is susceptible to arginine-specific mono(ADP-ribosyl)ation catalyzed by CT.

ADP Ribose Transferases↗
PubMed1991

Diagnosis of cysticercosis in endemic regions. The Cysticercosis Working Group in Peru.

Taenia solium cysticercosis is a frequent cause of neurological disease in developing countries. Specific diagnosis of cysticercosis is difficult. We obtained serum and/or CSF samples from 204 consecutive patients admitted to a neurological ward in Lima, Peru, and looked for antibodies specific for T solium with the enzyme-linked immunoelectrotransfer blot (EITB) assay. 21 (12%) of 173 serum samples from these patients were EITB-positive. In contrast, only 2 (1.5%) of 135 patients attending a public endoscopy clinic and 1 (1%) of 88 patients attending a private endoscopy clinic were seropositive. 1 (1%) of 98 pregnant women living in a Lima shanty town was EITB-positive. 15 (58%) of 26 neurology patients diagnosed clinically as having cysticercosis were seronegative. Routine screening by EITB of all patients with neurological symptoms from areas of endemic cysticercosis would avoid misdiagnosis of this common and treatable disease.

Adolescent↗
PubMed1991

Visual motion perception from stimulation of the human medial parieto-occipital cortex.

Visual phenomena evoked by direct electrical stimulation of extrastriate cortex were observed in 30 epileptic patients as part of a presurgical investigation. An incremental sequence of low-level bipolar stimulation trains was delivered at medial and lateral pairs of contacts of stereotaxically-implanted multilead intracerebral electrodes in parietal, occipital and posterior temporal regions. Diffusion of stimulus afterdischarges was monitored by electrodes in temporal and frontal lobes and by the non-stimulated contacts of the stimulated electrode. Localized stimulations evoked few visual phenomena. The strongest anatomo-perceptual correlation was found for stimulation in the medial parieto-occipital fissure which evoked visual motion phenomena in all three patients stimulated in that region. The evoked motion perceptions were not associated with eye movements or any particular localization of the epileptic focus. These perceptions were only evoked once outside of the medial PO region at the 61 sites examined. The results suggest that the medial parieto-occipital region is closely linked to the human visual motion processing system.

Brain Mapping↗
PubMed1991

Long-term effects of depot-medroxyprogesterone acetate on lipoprotein metabolism.

To assess the effects of depot-medroxyprogesterone acetate (DMPA) upon serum lipids and lipoproteins, a comparative study in chronic users and new acceptors was undertaken. Two groups of women of reproductive age were included in the study; group I (n = 8) was formed by new acceptors whereas, group II (n = 14) constituted DMPA users of more than five continuous years (7.0 + 2.1 years). Blood samples were taken on the day of injection and 15, 29, 57 and 92 days after the i.m. administration of 150 mg of DMPA for the measurement of total triglycerides (TG), cholesterol (CHOL) and phospholipids (PHL). In addition, the TG and CHOL content in the very low density (VLDL), low density (LDL) and high density (HDL) lipoprotein fractions obtained by ultracentrifugation were also determined. The results demonstrated a moderate increase in the serum total TG concentrations at the expense of the VLDL fraction in the group of chronic DMPA users. In both groups, the administration of DMPA induced a moderate, though not significant, decrease in total CHOL and HDL-chol, an effect that was noticed at the end of the treatment interval; the serum LDL-chol content remained unchanged. In addition, a decrease in the total serum phospholipids content was noticed after DMPA injection in both groups, which resembled the fluctuations observed in the luteal phase of normal ovulating women. The overall data indicate that acute and/or chronic DMPA administration at the dose currently employed for contraception does not induce major abnormalities in lipoproteins in serum.

Adult↗
PubMed1991

A retrospective study of disposable extended-wear lenses in 100 patients.

A retrospective evaluation of 100 patients who wore disposable extended-wear contact lenses is presented. The patients were selected at random and were fitted with one of three lens brands approved for extended wear. There were 37 males and 63 females in the study. The mean age was 40.1 years (range, 14 to 76 years). Sixty-seven of the patients wore nondisposable extended-wear soft contact lenses before being fitted with disposable lenses. Complications were noted and included two instances of infectious ulcerative keratitis and six cases of peripheral corneal infiltrates. It is believed that the rate of complications is due to the ongoing hypoxic effect of prolonged use of extended-wear or other contact lenses and may be improved by providing a greater variety of lens fitting parameters. Disposable extended-wear lenses may be a reasonable means of vision correction in the appropriately selected patient and with proper follow-up. At the same time, caution should be exercised in the fitting and wear of disposable extended-wear lenses.

Adolescent↗
PubMed1991

Detection of linkage for heterogeneous disorders by using multipoint linkage analysis.

We have compared the efficiency of the lod score test which assumes heterogeneity (lod2) to the standard lod score test which assumes homogeneity (lod1) when three-point linkage analysis is used in successive map intervals. If it is assumed that a gene located midway between two linked marker loci is responsible for a proportion of disease cases, then the lod1 test loses power relative to the lod2 test, as the proportion of linked families decreases, as the flanking markers are more closely linked, and as more map intervals are tested. Moreover, when multipoint analysis is used, linkage for a disease gene is more likely to be incorrectly excluded from a complete and dense linkage map if true genetic heterogeneity is ignored. We thus conclude that, in general, the lod2 linkage test is more efficient for detecting a true linkage when a complete genetic marker map is screened for a heterogeneous disorder.

Child↗
PubMed1991

Comparative study between intact PTH and fragments of PTH in patients on hemodialysis and CAPD.

Twenty-nine patients on hemodialysis (HD) and 29 patients on continuous ambulatory peritoneal dialysis (CAPD) were studied. Serum calcium and phosphorous levels were similar in the 2 groups. Serum parathyroid hormone (PTH) levels were determined by 4 different methods. Mid-molecule PTH levels were higher in HD (1099.5 +/- 876.8 pmol/L) than in CAPD patients (541.0 +/- 138.8 pmol/L), p less than 0.001, while intact PTH levels were similar. The ratio MM-PTH/Intact PTH was higher in HD (55.2 +/- 29.0) than in CAPD patients (39.0 +/- 20.0), where p less than 0.01. In patients with similar C-PTH, those on CAPD had higher levels of intact PTH (46.0 +/- 27.0 pmol/L) than those in HD (29.3 +/- 29.0 pmol/L), p less than 0.01. The ratio C-PTH/intact PTH was higher in HD (104.9 +/- 39.6) than in CAPD patients (59.3 +/- 32.3), p less than 0.001. The Peritoneal Saturation Index (PSI) of MM-PTH was 23.4 +/- 12%, and it showed a hyperbolic correlation in respect to MM-PTH serum levels. We concluded that CAPD can modify the plasma C-PTH and MM-PTH serum levels by peritoneal losses of these fragments.

Humans↗
PubMed1991

The use of Saturn II lenses in keratoconus.

We studied Saturn II contact lenses in keratoconus patients who were intolerant to other available contact lenses. A total of 24 patients, who were followed for up to 15 months, participated in the study. Visual acuities improved significantly following fitting with the Saturn II contact lens; whereas only one eye in the series was correctable to 20/20 before fitting, eight eyes were corrected to 20/20 following fitting. A great number of lenses had to be replaced during the study because of deposit formation and tearing at the interface (rate of replacement: 0.52 lenses per eye per month). A variety of complications occurred during lens wear, resulting in only six eyes wearing the Saturn II lens at the close of the study (out of 46 eyes that had started wearing the lens). Discomfort due to tightness of the peripheral segment was the most common cause of lens discontinuation. We conclude that the Saturn II lens was inadequate for fitting patients with advanced keratoconus.

Adolescent↗
PubMed1990

Power of the linkage test for a heterogeneous disorder due to two independent inherited causes: a simulation study.

We have conducted a simulation study in small pedigrees to investigate the power to detect linkage and heterogeneity for a disorder due to either one of two independent disease loci. We have considered a highly polymorphic marker locus (PIC = 70%) linked to one disease locus and unlinked to the second. The power to detect linkage has been examined by using the admixture test. We have varied the mode of transmission of each disease locus, the ascertainment of families and the proportion of cases in the population due to the linked disease locus. Generally, for the multiplex ascertainments we have considered, the power to detect linkage is greater when the linked disease locus has a high penetrance, when the unlinked disease locus has a low penetrance, and when pedigrees with multiple affected are selected. When selecting families with multiple affected, the rate of "mixed" families (i.e., those segregating for both disease loci) increases. However, for the pedigree structure we have considered, the power of the linkage test is more affected by a decrease in the rate of "linked" families than by an increase in the rate of "mixed" families. Finally, the present study shows that detection of linkage in presence of heterogeneity is feasible with a realistic sample size of small pedigrees as long as the linked disease locus accounts for more than 25% of the cases.

Genetic Carrier Screening↗