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Biomedical subjects

J Opitz

Publications and source records attributed to J Opitz.

14 recordsLinked to original sources
PubMed2006

Photolabile carboxylic acid protected terpolymers for surface patterning. Part 2: Photocleavage and film patterning.

The surface properties of films made of p-methoxyphenacyl derivative terpolymers, associated with photocleavage by UV irradiation, and their optical patterning are investigated. The deprotection reaction has been monitored by UV and FTIR spectroscopy, contact angle measurements, and X-ray photoelectron spectroscopy, revealing the photoremoval of the protecting p-methoxyphenacyl group in high yields under mild conditions. Parallel and serial patterning of the films has been performed by selective irradiation through optical masks and by laser irradiation via fiber tips of a scanning near-field optical microscope, respectively. By irradiation of photolabile protected functional groups, free carboxylic groups become exposed to the surface with which fluorescent dyes and proteins can be associated specifically.

Carboxylic Acids↗
PubMed1999

Syndromal (and nonsyndromal) forms of male pseudohermaphroditism.

The term sex determination refers to the genetic events that bring about male or female gonadal development; sex differentiation to all subsequent morphogenetic and physiological events that establish functional sexuality, sexual dimorphism and the secondary sexual characteristics. Virtually all of the steps of sex differentiation are under genetic control; consequently each one of them can fail as result of mutation of the corresponding genes. We shall be concerned with those genes and their mutations that cause pseudohermaphroditism in males and more rarely in females (with the exception of congenital adrenal hyperplasia). Special emphasis will be placed on Swyer, Denys-Drash, RSH, GBBB, campomelic and ATR-X syndromes, whose genes were recently identified.

Animals↗
PubMed1997

Evaluation of mental retardation: recommendations of a Consensus Conference: American College of Medical Genetics.

A Consensus Conference utilizing available literature and expert opinion sponsored by the American College of Medical Genetics in October 1995 evaluated the rational approach to the individual with mental retardation. Although no uniform protocol replaces individual clinician judgement, the consensus recommendations were as follows: 1. The individual with mental retardation, the family, and medical care providers benefit from a focused clinical and laboratory evaluation aimed at establishing causation and in providing counseling, prognosis, recurrence risks, and guidelines for management. 2. Essential elements of the evaluation include a three-generation pedigree: pre-, peri-, and post-natal history, complete physical examination focused on the presence of minor anomalies, neurologic examination, and assessment of the behavioral phenotype. 3. Selective laboratory testing should, in most patients, include a banded karyotype. Fragile X testing should be strongly considered in both males and females with unexplained mental retardation, especially in the presence of a positive family history, a consistent physical and behavioral phenotype and absence of major structural abnormalities. Metabolic testing should be initialed in the presence of suggestive clinical and physical findings. Neuroimaging should be considered in patients without a known diagnosis especially in the presence of neurologic symptoms, cranial contour abnormalities, microcephaly, or macrocephaly. In most situations MRI is the testing modality of choice. 4. Sequential evaluation of the patient, occasionally over several years, is often necessary for diagnosis, allowing for delineation of the physical and behavioral phenotype, a logical approach to ancillary testing and appropriate prognostic and reproductive counseling.

Diagnosis, Differential↗
PubMed1993

Identification of a novel sequence element in the common promoter region of human collagen type IV genes, involved in the regulation of divergent transcription.

The expression of the heterotrimeric collagen IV molecule alpha 1(IV)2 alpha 2(IV) is essential for the structural integrity and functional properties of all basement membranes. The two genes COL4A1 and COL4A2 that code for the subunits are found closely linked on chromosome 13 in a head-to-head arrangement and are transcribed in divergent directions. We have identified a novel trans-acting factor that binds in vitro to a unique homopyrimidine/homopurine stretch within the shared promoter region of the two collagen IV genes. Additional binding sites have been identified within the first introns of both genes and the consensus sequence CCCTYCCCC for efficient binding has been deduced; the factor was named therefore 'CTC-binding factor' or 'CTCBF'. Mutations in the binding site of CTC-binding factor within the promoter inhibited binding in vitro and resulted in reduced transcription from both genes. The effect of mutations on the transcription of COL4A2 is more pronounced than on the transcription of COL4A1. CTC-binding factor is a nuclear factor that binds dominantly in vitro to the collagen IV promoter and is involved in regulating the expression of both collagen IV genes.

Base Sequence↗
PubMed1993

A 354-gram infant: 48 month follow-up.

Extreme prematurity (birth weight less than 500 g) with intact survival is very uncommon. This paper describes a preterm infant with birth weight of 354 g who is now 4 years old and developmentally normal. Intervention and management decisions in such a low birth weight group produce an ethical enigma. Survival of newborns with a birth weight less than 400 g is unusual. Decisions regarding intervention and care for extremely low birth weight infants impact on financial, emotional, and medical responsibilities of family members and health care professionals. It has been increasingly difficult to set guidelines or policies regarding resuscitation of "micropremies" based on weight and gestational age.

Adult↗
PubMed1990

Single- and double-strand break formation in double-stranded DNA upon nanosecond laser-induced photoionization.

Double-stranded (ds) calf thymus DNA (0.4 mM), excited by 20 ns laser pulses at 248 nm, was studied in deoxygenated aqueous solution at room temperature and pH 6.7 in the presence of a sodium salt (10 mM). The quantum yields for the formation of hydrated electrons (phi c-), single-strand breaks (phi ssb) and double-strand breaks (phi dsb) were determined for various laser pulse intensities (IL). phi c- and phi ssb increase linearly with increasing IL; however, phi ssb has a tendency to reach saturation at high IL (greater than 5 X 10(6) Wcm-2). The ratio phi ssb/phi c-, representing the number of ssb per radical cation, is about 0.08 at IL less than or equal to 5 X 10(6) Wcm-2. For comparison, the number of ssb per OH radical reacting with dsDNA is 0.22. On going from argon to N2O saturation, phi ssb and phi dsb become larger by factors of approximately 5 and 10-15, respectively. This enhancement is produced by attack on DNA bases by OH radicals generated by N2O-scavenging of the photoelectrons. While phi ssb is essentially independent of the dose (Etot), phi dsb depends linearly on Etot in both argon- and N2O-saturated solutions. The linear dependence of phi dsb implies a square dependence of the number of dsb on Etot. This portion of dsb formation is explained by the occurrence of two random ssb, generated within a critical distance (h) in opposite strands. For both argon- and N2O-saturated solutions h was found to be of the order of 40-70 phosphoric acid diester bonds. On addition of electron scavengers such as 2-chloroethanol (or N2O plus t-butanol), phi dsb is similar to that in neat, argon-saturated solutions. Thus, hydrated electrons are not involved in the chemical pathway leading to laser-pulse-induced dsb of DNA.

DNA↗
PubMed1985

Model studies for the direct effect of high-energy irradiation on DNA. Mechanism of strand break formation induced by laser photoionization of poly U in aqueous solution.

Laser flash photolysis of polyuridylic acid (poly U) in anoxic aqueous solutions leads to biphotonic photoionization of the uracil moiety followed by the formation of single strand breaks (ssb). The rate constant for ssb formation (1.0 s-1, obtained from the slow component of conductivity increase at 23 degrees C and pH 6.8) increases with decreasing pH to 235 s-1 at pH 3.5. The activation energy (pre-exponential factor) was measured to be 66 kJ mol-1 (5 X 10(11) s-1) at pH 6.8. Addition of dithiothreitol (DTT) or glutathione (GSH) prevents ssb formation by reacting with a poly U intermediate (rate constant = 1.2 X 10(6) and 0.16 X 10(6) dm3 mol-1 s-1, respectively). Since with OH radicals as initiators very similar data have been obtained for the kinetics of ssb formation and for the reaction with DTT, we conclude that photoionization of the uracil moiety in poly U leads eventually to the same chemical pathway for ssb formation as that induced by OH radicals. Furthermore, we propose that protection by DTT and GSH occurs via H donation to the C-4' radicals of the sugar moiety of DNA and to the C-4' and the C-2' radicals of poly U.

DNA↗
PubMed1977

Defect of cerebellar Purkinje cell histogenesis associated with type I and type II renal cystic disease.

The cerebellar vermises from a 1 day old child who died with cystic dysplastic kidneys (Potter Type II) and from a 28 day old who died with infantile polycystic kidneys (Potter Type I) were studied by the Golgi silver method and electron microscopical procedures. Golgi stains showed that Purkinje cells from both cases had the following abnormal characteristics: (1) they retained perikaryal processes even at 37-42 weeks after conception although these processes are normally absent from the cerebellar vermis after 34 weeks of gestation; (2) The Purkinje cell dendrites had dilations at their numerous branchpoints. Ultrastructural studies indicated that climbing fibers remained in contact with the perikaryon of the Purkinje cell in both cases although they are not normally present on the perikaryon after 33 weeks gestation. The 1 day old child (Type II) had unusual synaptic structures of the dyad and serial type. The concurrence of cerebellar and kidney cell maldevelopment in this and a variety of other conditions suggests that there may be a pathogenetic and causal relationship between the two.

Cerebellum↗
PubMedDate not supplied

Prospective study of clinical findings and changes in 56 Trilucent implant explantations.

Between 1995 and 1998 we implanted 88 Trilucent implants in 48 patients. The experience of 56 explantations in 30 patients are presented in this prospective study. Of 48 patients, 32 returned for review after we wrote to them. Twenty-seven elected to have their implants exchanged immediately for a fourth-generation cohesive silicon implant and three decided to have the implants removed and not replaced. In 14 patients it was clinically obvious that the volume of the implant had changed, although not all patients realized this. The absence of capsular contraction was notable (unanimously Baker II), so that most patients were asymptomatic and had to be convinced of the need for explantation. However, perioperatively, 55% of the implants had thickening or color change caused by the peroxidation of the triglyceride content. Typically the implant capsule was adherent to the surrounding tissues, especially pectoralis major. This prolonged operative time (184 min, on average) and hemostasis was a problem. During the study we developed a standardized operative technique, which enabled us to reduce operative times. Special attention had to be paid to the selection of the new implant volume, because many patients had become accustomed to the increase in the size of their breasts caused by the peroxidation of the implant content. Forty-three percent of patients preoperatively expressed the wish to have even bigger breasts than before. Nearly all of our patients at the three-month postoperative follow-up were happier with the new implants than before. It became apparent that after only two to three years there were obvious oxidative changes in the implants in asymptomatic patients. Based on our study result, the recommendations regarding explantation of Trilucent implants seem justified.

Breast↗