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Biomedical subjects

S Parks

Publications and source records attributed to S Parks.

At least 55 records · Page 3Linked to original sources
PubMed1986

Replication and expression of an X-linked cluster of Drosophila chorion genes.

Two 80- to 100-kb chromosomal replicons containing clustered chorion genes amplify in the ovarian follicle cells during the final 22 hr of Drosophila oogenesis. We have studied the relationship between amplification and transcription within one of these domains, located at 7E10-7F3,4 on the X chromosome. A tandem cluster of six genes, encoding chorion structural proteins s36-1, s38-1, and four putative minor chorion protein mRNAs, was mapped in the central 18 kb of the amplified domain, a region showing the highest levels of amplification. The regions both proximal and distal to this gene cluster, where lower levels of amplification occur, were also transcribed in ovary, but mRNAs produced specifically during choriogenesis were not detected. Thus, differences in amplification do not appear to modulate differential RNA accumulation. Instead, the gradient of amplification observed in egg chamber DNA may simply reflect the mechanism of amplification. In the female sterile mutation, In(1)ocelliless, a chromosomal rearrangement separates the central gene cluster into two parts, only one of which retains the capacity to amplify. Genes located within the unamplified portion of the ocelliless chromosome were expressed at the appropriate time during oogenesis, but at a 5- to 10-fold reduced level of RNA per gene. Thus neither cluster integrity nor amplification are required for the normal developmental program of gene expression within the cluster.

Animals↗
PubMed1986

Storage and transportation of lymphoid tissue for immunophenotyping.

Immunoperoxidase staining of frozen sections is a cost-effective technic for immunophenotyping cells of lymphoid tissue. Because this procedure is not performed in many institutions, a simple method to transport fresh tissue to centers performing these studies is required. Tissues in saline at refrigerator temperature may be successfully transported. In addition, in order to minimize laboratory expenses, lymphoid tissue can be kept refrigerated in saline until permanent sections are examined and immunodiagnostic procedures become necessary. In this study reproducible immunophenotyping of 12 samples of lymphoid tissue stored up to seven days was achieved.

Antibodies, Monoclonal↗
PubMed1980

Lipogranulomatosis of the genitalia caused by topical application of "baby oil".

A case is reported of lipogranulomatosis of the genitalia caused by topical application of "baby oil". To our knowledge this is the first such case reported in the English literature. The chemical nature of the lipid in question was analyzed by sophisticated procedures, including gas liquid chromatography, thin layer chromatography and mass spectrometry. After the etiologic agent was defined retrospective questioning of the patient confirmed the diagnosis.

Administration, Topical↗
PubMedDate not supplied

Comparison of repeatability of the multifocal electroretinogram and Humphrey perimeter.

Functional mapping of the retina by multifocal electroretinographic recordings is now possible. We compared the normal range, repeatability and response topography of this new technique with conventional static Humphrey perimetry to assess its suitability in clinical practice. The multifocal technique was performed on 60 age-matched controls. Measures of repeatability and reproducibility were obtained. Results were then compared with those obtained from a customized perimetry test. In both tests the coefficients of repeatability were found to decrease with eccentricity. The inherent measurement variation between techniques was comparable. Overall system variation indicates that the technique could be a useful tool at the clinical level.

Computer Graphics↗
PubMedDate not supplied

The effect of filter bandwidth on the multifocal electroretinogram.

The effect of filter bandwith on the multifocal electroretinogram was assessed by means of theoretical calculation, electronic simulation and real multifocal electroretinogram recordings. Waveform distortion by high-pass filtering on simulated square waves, normal electroretinogram waveforms and negative electroretinogram waveforms was demonstrated. The theory of the effect of differentiation on electroretinogram waveform shape by electronic filtering indicates that little effect would be observed by changing the input filter cut-off for normal electroretinographic waveform shapes. However, negative electroretinogram waveforms are differentiated when the high-pass filter setting is increased. The differentiation effect artificially recreates a positive component that could be mistaken as a b-wave component. To eliminate this effect when recording multifocal electroretinograms, a high-pass filter setting of less than 1 Hz should be used to preserve the true electroretinographic waveform shape.

Computer Simulation↗
PubMedDate not supplied

An instrument to investigate temporal processing mechanisms with the multifocal ERG.

The multifocal ERG technique is a powerful method of studying the function of different areas of the retina. Display systems such as the CRT, which are commonly used for stimulation, are subject to limitations such as those imposed by the raster method of scanning. This work describes a novel stimulating display using LEDs that retains the established hexagonal areas but overcomes some of the limitations of the CRT display systems. The design and construction of the instrument is described together with some preliminary results.

Electroretinography↗
PubMedDate not supplied

Effect of implanted insulin pumps on fluorescein transcapillary escape time in type 1 diabetes mellitus.

OBJECTIVE: To determine whether significant increases in fluorescein transcapillary escape time (FTET) would occur after treatment of patients with type 1 diabetes with insulin delivered intraperitoneally by a surgically implanted pump. METHODS: Nine patients with type 1 diabetes who were otherwise healthy and had received surgically implanted insulin pumps on a study protocol were recruited to have three measurements of FTET and glycosylated hemoglobin during an 18-month period. Serum fluorescein-albumin binding was measured at the time of the final test. Control FTETs were measured in 46 patients with type 1 diabetes who did not have insulin pumps and in 15 adults without diabetes. RESULTS: In the implanted insulin pump group, 50% of the FTETs were below normal, but no significant longitudinal change in FTETs was noted in eight of the nine study patients. The mean FTETs in the implanted insulin pump group were significantly higher than those of the control patients with diabetes but without insulin pumps (mean, 88 versus 62 seconds; P<0.05) but significantly lower than those of the control subjects without diabetes (88 versus 163 seconds; P<0.001). Four of the nine patients with implanted insulin pumps had normal FTETs on all three studies. This subgroup had used insulin pumps (external + implanted) for significantly longer periods (6.2 versus 2.6 years; P<0.05) than the other five patients. These differences within the implanted pump group did not correlate with differences in glycosylated hemoglobin values or fluorescein-albumin binding; however, the glycosylated hemoglobin levels before insulin pump implantation were significantly lower than those of the other five patients. Three patients with onset of type 1 diabetes before age 10 years had the lowest FTETs. CONCLUSION: Implanted insulin pumps did not alter FTETs between 6 months and 32 months after pump implantation. Total time on insulin pumps (external and implanted) is associated with normal FTET, and onset of diabetes before age 10 years is associated with abnormal FTET.

Journal Article↗