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Biomedical subjects

J Crooks

Publications and source records attributed to J Crooks.

At least 19 recordsLinked to original sources
PubMed1996

Neuroendocrine (carcinoid) tumor of the mandible: a case report and review of the literature.

The aim of this article is to present a case of primary neuroendocrine tumor (typical carcinoid) of the mandible that occurred in a 46-year-old black woman who was seropositive for the human immunodeficiency virus. Radiologically the lesion presented as a poorly circumscribed honeycomb radiolucency that extended from tooth 21 to the ascending ramus. Histologically the tumor cells were variously arranged in small islands, trabeculae, follicles, and slitlike spaces lined by a single layer of palisaded low-columnar cells. The follicles contained an eosinophilic colloid-like substance. Immunocytochemical staining showed diffuse, intense positivity for MAK 6, pancytokeratin, S-100, and neuron-specific enolase and focal, intense, positive staining for chromogranin A. Electron microscopy showed the presence of interdigitating cell membranes, rudimentary cell attachments, and varying numbers of membrane-bound dense core granules. Special investigations failed to reveal a primary tumor, and no metastases were found. Urine and hematologic assessment did not show any evidence of functional activity. The tumor was resected, and no recurrence or spread has been seen for 2 years. Origin from foregut-derived, immature, and functionally uncommitted endocrine cells is presumed.

Carcinoid Tumor↗
PubMed1995

Quantitative analysis of synaptogenesis in the inner plexiform layer of macaque monkey fovea.

Synaptogenesis has been tracked by using quantitative electron microscopic methods in the inner plexiform layer (IPL) of the developing Macaca monkey fovea from fetal day (Fd) 55 to Fd132. Vesicle-containing profiles were classified according to whether (1) they contained a ribbon indicating that they originated from a bipolar cell, or (2) the profile formed a junction. Group 2 was further subdivided by morphological characteristics into (2a) amacrine, (2b) bipolar, or (2c) unknown profiles. Ribbon-containing bipolar profiles are clearly identifiable at Fd55 when they occur at a density of 0.9/100 microns2. Bipolar synapses increase rapidly to 4.7/100 microns2 by Fd88, similar to their density at Fd132. Identifiable amacrine profiles forming a junction are rare at Fd55-68. By Fd88, amacrine synaptic density has jumped to 6.7/100 microns2 and continues to increase to 9.5/100 microns2 at Fd132. These quantitative data strongly suggest that, at the Macaca fovea, bipolar synaptogenesis both begins and ends before amacrine synaptogenesis. The large number of immature amacrine synaptic profiles and densities at Fd132 suggests that amacrine synapses continue to form after Fd132. This study confirms that cone-dominated monkey fovea has a different sequence of synaptogenesis than the rod-dominated peripheral retina (Nishimura and Rakic, [1985] J. Comp. Neurol 241:420-434). The data support the concept that synaptic developmental sequence is determined by the type of photoreceptor which dominates a particular retinal region or species. Bipolar ribbon synapses are observed in the outer half of the IPL at Fd55, are present in the inner IPL at Fd60, and then, with increasing age, are found throughout the IPL. This pattern strongly suggests that vertical OFF bipolar pathways form earlier than ON pathways in the IPL. In contrast, amacrine profiles are found throughout the IPL at the youngest ages, with an adult-like banding pattern present by Fd132.

Age Distribution↗
PubMed1994

A randomized trial of acyclovir for 7 days or 21 days with and without prednisolone for treatment of acute herpes zoster.

BACKGROUND: Acyclovir given for 7 to 10 days is of proved benefit in acute herpes zoster, but studies of its effectiveness in preventing postherpetic neuralgia have had conflicting results. The role of corticosteroids in the treatment of herpes zoster is also controversial. METHODS: We conducted a double-blind, controlled trial in patients with acute herpes zoster to determine whether either 21 days of acyclovir therapy or the addition of prednisolone offered any improvement over 7 days of acyclovir therapy. Patients with a rash of less than 72 hours' duration were assigned to receive acyclovir (800 mg orally, five times daily) for 7 days with either prednisolone or placebo, or acyclovir for 21 days with either prednisolone or placebo. Prednisolone therapy was initiated at a dose of 40 mg per day and tapered over a three-week period. Patients were assessed frequently through day 28 and then monthly through month 6 to assess postherpetic neuralgia. RESULTS: Of 400 patients recruited, 349 completed the study. No significant differences were detected between the four groups in the progression of the rash (P > 0.1). With steroid therapy, a significantly higher proportion of the rash area had healed on days 7 and 14 (P = 0.02). Pain reduction was greater during the acute phase of disease in patients treated with steroids or 21 days of acyclovir (P < 0.01 and P = 0.02, respectively, on day 7; P < 0.01 for steroid therapy on day 14). However, on follow-up there were no significant differences between any of the groups in the time to a first or a complete cessation of pain. The steroid recipients reported more adverse events. CONCLUSIONS: In acute herpes zoster, treatment with acyclovir for 21 days or the addition of prednisolone to acyclovir therapy confers only slight benefits over standard 7-day treatment with acyclovir. Neither additional treatment reduces the frequency of postherpetic neuralgia.

Acute Disease↗
PubMed1992

Localization of GABA, glycine, glutamate and tyrosine hydroxylase in the human retina.

A light microscope study using postembedding immunocytochemistry techniques to demonstrate the common neurotransmitter candidates gamma-aminobutyric acid (GABA), glycine, glutamate, and tyrosine hydroxylase for dopamine has been done on human retina. By using an antiserum to GABA, we found GABA-immunoreactivity (GABA-IR) to be primarily in amacrine cells lying in the inner nuclear layer (INL) or displaced to the ganglion cell layer (GCL). A few stained cells in the INL, which are probably interplexiform cells, were observed to project thin processes towards the outer plexiform layer (OPL). There were heavily stained bands of immunoreactivity in strata 1, 3 and 5 of the inner plexiform layer (IPL). An occasional ganglion cell was also GABA-IR. By using an antiserum to glycine, stained cells were observed at all levels of the INL. Most of these were amacrines, but a few bipolar cells were also glycine-IR. Displaced amacrine cells and large-bodied cells, which are probably ganglion cells, stained in the GCL. The bipolar cells that stained appeared to include both diffuse and midget varieties. The AII amacrine cell of the rod pathway was clearly stained in our material but at a lower intensity than two other amacrine cell types tentatively identified as A8 and A3 or A4. Again, there was stratified staining in the IPL, with strata 2 and 4 being most immunoreactive. An antiserum to glutamate revealed that most of the neurons of the vertical pathways in the human retina were glutamate-IR. Rod and cone photoreceptor synaptic endings labeled as did the majority of bipolar and ganglion cells. The rod photoreceptor stained more heavily than the cone photoreceptor in our material. While both midget and diffuse cone bipolar cell types were clearly glutamate-IR, rod bipolars were not noticeably stained. The most strongly staining glutamate-IR processes of the IPL lay in the outer half, in sublamina a. The antiserum to tyrosine hydroxylase (TOH) revealed two different amacrine cell types. Strongly immunoreactive cells (TOH1) had their cell bodies in the INL and their dendrites ramified in a dense plexus in stratum 1 of the IPL. Fine processes arising from their cell bodies or from the stratum 1 plexus passed through the INL to reach the OPL but did not produce long-ranging ramifications therein. The less immunoreactive amacrines (TOH2) lay in the INL, the center of the IPL or the GCL and emitted thick dendrites that were monostratified in stratum 3 of the IPL.

Aged↗
PubMed1992

Ameloblastoma with dentinoid induction: dentinoameloblastoma.

Ameloblastomas do not generally show evidence of induction, however rare cases associated with an odontome have been reported, and are referred to as odontoameloblastoma. In this paper the first known case of an ameloblastoma showing evidence of induction of dentinoid by tumor cells but without concomitant formation of enamel is recorded. The lesion occurred in the angle and ramus of the mandible of a 24-yr-old Asian man and was largely unicystic. In one area however, solid tumor was present which consisted both of infiltrating follicles of typical ameloblastoma tissue and solid sheets of ovoid to spindle cells containing abundant amounts of a homogenous eosinophilic extracellular material, interpreted as dentinoid, and psammamomatous type dystrophic calcifications. Electron microscopic examination of formalin-fixed tissue showed this dentinoid material to consist of interlacing collagen fibrils embedded in a structureless ground substance. At the periphery of the dentinoid globules the collagen fibres were arranged in parallel layers. A final diagnosis of dentinoameloblastoma was made.

Adult↗
PubMed1989

A conformational immunogen on VP-2 of infectious bursal disease virus that induces virus-neutralizing antibodies that passively protect chickens.

VP-2b, a major structural protein of infectious bursal disease virus (IBDV), and its precursor protein VP-2a were separated in a soluble form from the supernatant of ultracentrifuged viruses by using a monoclonal antibody specific for VP-3, the other major structural protein, to remove soluble VP-3 and remaining virus particles. The native VP-2a/2b inhibited the majority of virus-neutralizing (VN) activity in chicken anti-IBDV sera and chickens immunized with VP-2a/2b produced VN antibodies that passively protected susceptible chickens from infection. However, the separated VP2a/2b was not as immunogenic as intact virus particles. VP-2a/2b would appear to contain a conformational epitope which is destroyed by SDS and boiling and which may prove to be of critical importance in a subunit vaccine against type 1 IBDV.

Adsorption↗
PubMed1989

Use of the avidin-biotin-peroxidase immunostaining technique on previously stained histologic sections.

A recent report has demonstrated that the avidin-biotin-peroxidase (ABP) technique can successfully be used on previously stained histologic sections without the loss of sensitivity. In this study the tissues had been microwave fixed and only H & E stained sections were used. This procedure was tested on formalin-fixed tissues previously stained with H & E, PAS and van Gieson. Stained sections were prepared from selected blocks used as controls. One week after staining the sections were decolorized and together with the unstained control sections were restained with the ABP technique using IgA, IgD, IgE, IgM, kappa and lambda light chains, S100, EMA, LCA, amylase and PCK antisera. Demonstration of the tissue antigens was best with the previously stained H & E slides with little or no loss in sensitivity. Variable results were obtained with the PAS and van Gieson slides, the loss of sensitivity varying from none to complete.

Avidin↗
PubMed1989

Synapses of the inner plexiform layer of the area centralis of kitten retina during postnatal development: a quantitative study.

The frequency of occurrence of conventional synapses in the inner plexiform layer of the area centralis of the kitten retina remained invariant with postnatal age while that of bipolar cell ribbon synapses increased significantly. A significant increase also occurred in the ratio of bipolar cell ribbons to conventional synapses. The counts were made from large montages of electron micrographs in 17 kittens of ages ranging from newborn to 200 days and also in 3 adults. It was confirmed that the observed results were not attributable to an age-related change in the size or orientation of the profiles during postnatal development. The distribution of conventional synapses showed a peak in the middle stratum of the inner plexiform layer which remained invariant with development. By contrast, the distribution of bipolar cell ribbons changed during development, with new ribbons being added to the inner part of the inner plexiform layer.

Animals↗
PubMed1986

Granular cell reaction to surgical glove powder.

The histopathologic features characteristic of the inflammatory response associated with starch powder used as a lubricant for surgical gloves were investigated by implanting starch granules into 3 separate sites on the right side of 8 male Wistar rats. On the opposite side, a sham-operated site and sites implanted with talc were used as controls. Two rats were killed at 1, 2, 3 & 4-week intervals and tissue from the implanted sites was assessed for distinctive features. It was found that a consistent feature of the starch-implanted sites was the presence of large histiocytes containing prominent PAS-positive, diastase-resistant inclusions. These cells were not found in the control sites and, thus, were considered characteristic of starch contamination in tissue, even in the absence of identifiable starch granules. A possible clinical case of reaction to starch, identified retrospectively, using these results is discussed.

Animals↗
PubMed1986

Denis Browne: colleague (1892-1967).

The purpose of this character study is not to assess the achievements of this great paediatric surgeon but to describe this extraordinary, adventurous, rebellious and difficult man, his intelligence, intellectual curiosity and intense interest in technical problems, as well as his bluntness of manner which was confusing and irritating to some of his colleagues. Denis Browne is described as a shy and sensitive nature, which made it difficult for him to establish ordinary human relationships, but also as a strangely aloof colleague with a flair for clothes, remarkable skills at riding, shooting, tennis, billiard and golf, and much admired by his juniors. Denis Browne is also described as a demon for work, a man who had the courage of his convictions and acted upon them. Those who understood him admired him to the point of idolatry but he was also considered as the supreme egotist not giving an inch in discussions and overriding many of his colleagues, making enemies of them as he went and then deeming himself greatly wronged by lack of recognition. With a more modest approach he might have had an easy life with his genius acclaimed by everyone, rather than a life of struggle against ignorance and prejudice which, all at the same, he greatly enjoyed.

England↗
PubMed1984

Side-effect 'tolerance' in elderly long-term recipients of benzodiazepine hypnotics.

The outcome of long-term benzodiazepine hypnotic therapy has been investigated in a group of elderly patients in the community; 220 receiving nitrazepam and 33 flurazepam. The estimated duration of therapy was as long as 15 years in some cases. More than half were taking doses greater than 5 mg and 15 mg, respectively, the majority on a regular nightly basis in accordance with the instructions on containers. The plasma concentrations of nitrazepam and the active desalkyl metabolite of flurazepam correlated positively with weight-related dose. In the case of desalkyl-flurazepam, but not nitrazepam, the levels were substantially higher than those previously reported in young individuals. There was sustained patient satisfaction with the effectiveness of the hypnotics and, despite the high plasma levels, little subjective or objective evidence of unwanted sedation, confusion or unsteadiness. The findings of the survey suggest the development of both pharmacodynamic tolerance to the unwanted sedative effects of these drugs and a degree of dependence in long-term recipients.

Aged↗
PubMed1984

Pharmacokinetics of cefotaxime and desacetyl-cefotaxime in neonates.

Cefotaxime was given to neonates as treatment of infection in a dose of 25 mg/kg 12 hourly by intravenous injection. Blood samples taken by heel-prick were specially treated to minimize any effect of haemolysis on the hydrolysis of cefotaxime. The mean peak plasma concentrations of cefotaxime on the first, second and third days of therapy were 43, 40 and 52 mg/l, respectively, with mean plasma half lives of 4.0, 2.7 and 3.2 h. The mean peak concentrations of desacetyl-cefotaxime were about a quarter of those of cefotaxime, which is in good agreement with adult studies, but much lower than those previously published in studies with neonates. These results emphasize the care that is necessary in the assay of body fluids and tissues for cefotaxime and desacetyl-cefotaxime if accurate results are to be obtained.

Cefotaxime↗
PubMed1984

The concept of medical auditing.

The contribution of drug utilisation studies on national, regional and local levels, to the quality control or audit of drug therapy is discussed. Two major types of audit, self-audit and peer-group audit, are outlined and examples presented illustrating how the concept of audit may be applied to therapeutics with special reference to drug information centres, feedback of drug prescribing data, and drug formularies. When drug information on prescribing practice from these sources is disseminated to the prescribers without value judgements being made, the component of self-audit is predominant in contrast to drug information dealing with prescribing appropriateness, in which peer-group opinion is expressed. Methods of capturing and disseminating data on prescribing practice which could be used in the auditing process are described. However, the greatest contribution to therapeutic audit lies with those responsible for medical training who should foster the quality of selfcriticism and the quest for high standards of prescribing practice in their students.

Data Collection↗
PubMed1983

Rational therapeutics in the elderly.

The potential for altered responsiveness to drugs in elderly patients together with their high frequency of multiple disease states for which drug therapy might be indicated makes it important to define certain basic principles of prescribing for them in order to obtain maximum efficacy with minimum unwanted effects. Many diseases from which the elderly suffer do not require drug treatment and, if it is required, the decision should be made in light of the pharmacokinetic and pharmacodynamic characteristics of the alternatives, the increased potential of certain drugs to produce adverse effects in the elderly and a regular review of the need for continued medication. In order to improve compliance with prescribing instructions, the minimum number of drugs and doses should be prescribed, the size, shape and colour of tablets and capsules should also determine choice, and attention paid to packaging and labelling. The methods by which the patient living at home can manage his/her medication effectively should be carefully considered.

Aged↗
PubMed1983

Aging and drug disposition--pharmacodynamics.

The pharmacodynamics of a drug is defined as the effect of the drug on physiological functions and pathological processes and can be modified in the elderly by (a) pharmacokinetics, (b) receptor sensitivity (or density), (c) impaired homeostasis or (d) pathology. The alterations in pharmacokinetics in the elderly often result in a reduction of the dose required to achieve the optimum pharmacodynamic effect. Changes in the sensitivity of receptors may be decreased in the elderly (perhaps by a diminution in the number of receptors) as in the case of the beta-adrenergic blockers, but increase in sensitivity may also be found as in the case of warfarin. Impairment of homeostatic mechanisms, while related to aging, are frequently produced by pathological processes and have an important influence on the pharmacodynamics of many drugs. The effect of the multiple pathology often found in the elderly is likely to be the dominant factor in changes in pharmacodynamics in this population. The interaction of the above factors results in a heterogeneity of pharmacodynamic response in the elderly which requires the careful monitoring of both the efficacy and toxicity of their drug treatment.

Aged↗