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Biomedical subjects

M Benjamin

Publications and source records attributed to M Benjamin.

At least 73 records · Page 4Linked to original sources
PubMed1990

The cranial cartilages of teleosts and their classification.

The structure and distribution of cartilages has been studied in 45 species from 24 families. The resulting data have been used as a basis for establishing a new classification. A cartilage is regarded as 'cell-rich' if its cells or their lacunae occupy more than half of the tissue volume. Five classes of cell-rich cartilage are recognised (a) hyaline-cell cartilage (common in the lips of bottom-dwelling cyprinids) and its subtypes fibro/hyaline-cell cartilage, elastic/hyaline-cell cartilage and lipo/hyaline-cell cartilage, (b) Schaffer's Zellknorpel, typified by the cartilage in the gill filaments of most teleosts examined, (c) elastic/cell-rich cartilage, such as that which supports the barbels and oral valves of catfish, e.g. Corydoras metae, (d) fibro/cell-rich cartilage, as in the submaxillary meniscus of Sphaerichthys osphromenoides, (e) cell-rich hyaline and (f) matrix-rich hyaline cartilage--both of which are common in the neurocranium and gill arches of most teleosts. The range of cartilages seen, and the predominant cartilage type, is recorded for each species and a list is provided of the tissues that most typify different organs or regions of the head. As a preliminary pointer to developmental relationships between the cartilages, note was taken of gradual transitions between one cartilage and another. It is suggested that hyaline-cell cartilage occupies a key position in teleosts as the most labile of the supporting tissues and is highly characteristic of Cypriniformes. The cartilage that best resembles mammalian hyaline cartilage (matrix-rich hyaline cartilage) has a very conservative distribution in different skeletal elements and the least number of associations with other tissues. It is well represented in Siluriformes.

Animals↗
PubMed1989

Hyaline-cell cartilage (chondroid) in the heads of teleosts.

The structure and distribution of hyaline-cell cartilage (chondroid) (HCC) in the heads of teleosts has been studied in 48 species from 16 families. The tissue is pale-staining and has closely-packed, hyaline cells that are separated by a small quantity of matrix. The matrix has only a mild affinity for alcian blue and the cells are not shrunken within lacunae. Two subtypes of the tissue are here described--fibrohyaline-cell cartilage (chondroid) where collagen fibres are prominent in the matrix, and lipohyaline-cell cartilage where fat and hyaline cells are intermingled. An elastic hyaline-cell cartilage has been described previously. Associations of HCC with dense fibrous connective tissue, mucochondroid, hyaline cartilage and bone are described. Lists are provided of membrane and cartilages bones to which the tissue is attached and of species in which it is common. Suitable 'type examples' for reference and for further study include the cartilage in the rostral folds of the red-tailed black shark, Labeo bicolor and the flying fox, Epalzeorhynchus kalopterus. HCC occurs in lips and rostral folds, in pre-palatine and submaxillary menisci, in ligaments, at the anterior end of the basihyal, in the pectoral girdle, in adhesive discs, in gill arches, beneath the basioccipital chewing pad, in barbels, next to the facial nerve, around the olfactory region and in the core of the nasal skin flaps. It is a particularly important tissue in cyprinids and related fish, and enormous masses of it are present in the black shark, Morulius chrysophekadion and the Hong Kong pleco, Pseudogastromyzon myersi. It acts as a damper against the contractions of the heart or the pressure of occluding pharyngeal teeth, and it provides the mouth region of bottom-dwelling, algal eaters with flexible support. In relation to Schaffer's classification of supporting tissues, I confirm a distinction between HCC and Zellknorpel.

Animals↗
PubMed1989

The development of hyaline-cell cartilage in the head of the black molly, Poecilia sphenops. Evidence for secondary cartilage in a teleost.

The development of hyaline-cell cartilage attached to membrane (dentary, maxilla, nasal, lacrimal and cleithrum) and cartilage (basioccipital) bones has been studied in the viviparous black molly, Poecilia sphenops. Intramembranous ossification commences before the first appearance of hyaline cells. As hyaline-cell cartilage is densely cellular and as that attached to the dentary, maxilla and cleithrum develops from the periosteum of these membrane bones, it must be regarded as secondary cartilage according to current concepts. It is also argued that the hyaline-cell cartilage attached to the perichondral bone of the basioccipital (a cartilage bone), could also be viewed as secondary. The status of the cartilage on the nasal and lacrimal bones is less clear, for it develops, at least in part, from mucochondroid (mucous connective) tissue. This is the first definitive report of secondary cartilage in any lower vertebrate. The tissue is therefore not restricted to birds and mammals as hitherto believed, and a multipotential periosteum must have arisen early in vertebrate evolution.

Animals↗
PubMed1988

Mucochondroid (mucous connective) tissues in the heads of teleosts.

The distribution and structure of mucochondroid tissues in the heads of teleosts has been studied in 56 species from 26 families. The tissues could also be called mucous connective tissue and have previously been known as basophilic gelatinous tissue. They are a heterogeneous group of tissues that contain fibroblasts (type example--the subcutaneous mucochondroid of the Cobitidae) or hyaline cells (type example--the mucochondroid around the medulla oblongata and spinal cord of Rasbora heteromorpha), embedded in a pale-staining matrix in which there are variable numbers of collagen fibres and blood vessels. Mucochondroid tissue is especially common beneath the skin, in labial folds, around olfactory and accessory olfactory sacs, in opercular valves and beneath the sensory epithelia of the stato-acoustic organ. The histochemistry of several mucochondroid tissues has been studied in Misgurnus anguillicaudatus, Acanthopsis choirorhynchus, Gnathonemus petersi and Cyclopterus lumpus. They have widely different amounts and types of glycoproteins, glycosaminoglycans and connective tissue fibres. The ultrastructure of subcutaneous mucochondroid is described in Acanthophthalmus semicinctus. Its cells contain little rough endoplasmic reticulum and a small Golgi apparatus, but numerous plasmalemmal vesicles, especially in the cell processes. The matrix contains 23-35 nm diameter granules, collagen and 11-12 nm diameter microfibrils. The similarities between mucochondroid and hyaline cell chondroid (cartilage) at the ultrastructural level, are more obvious than their differences.

Animals↗
PubMed1988

Medical ethics and economics of organ transplantation.

Should organ transplants be available to all, regardless of ability to pay? Are organ transplants diverting funds from other, more basic medical needs? These are some of the economic questions of transplantation facing the medical profession and society in general. With the development of dialysis in the 1960s came the agonizing question of who should benefit from the limited number of kidney machines. This was resolved in 1972 when Congress extended Medicare benefits to patients with end-stage renal disease who were not federal employees or covered by VA benefits. But the economic fallout from the costs of such treatment underlies much of the reluctance to make access to heart and liver transplants available to everyone who would benefit from them. Some argue that if kidney transplants are available to all regardless of ability to pay, why should the same not be true of heart and liver transplants? The counterargument favors other uses for the funds, such as investing in basic research, education, and other preventive strategies and meeting the basic health needs of the uninsured. One argument for equal access to transplantation is that organs are donated for the good of the public as a whole, not just for those who can afford the operations, and that individuals and their families are asked to donate organs regardless of their financial status. Therefore, if organs are to be regarded as a public resource, they should be available to all, regardless of ability to pay.

Advisory Committees↗
PubMed1987

Pituitary cysts and concretions in the gasterosteidae (Teleostei).

Pituitary cysts in the nine-spined stickleback, Pungitius pungitius, were found in the prolactin zone of the rostral pars distalis in 22 per cent of fish caught in May from freshwater, field-drainage ditches near Cardiff, Wales. They were not associated solely with some special environmental or hereditary factor in the Welsh population, for they were also present in 6 per cent of fish caught at a similar time of year in a freshwater lake at Manitoba, Canada. Although the pituitaries of other sticklebacks (Culaea inconstans, Apeltes quadracus and Gasterosteus wheatlandi) are similar to that of P. pungitius, they did not develop large cysts. There were no cysts at all in A. quadracus, and none greater than 50 microns in diameter in C. inconstans and G. wheatlandi. A minority of P. pungitius (less than 1 per cent) develop concretions either within the pituitary ("intraglandular") or in the surrounding capsule ("capsular"). Most of the concretions are filled with a strongly staining and laminated colloid. They are present in males and females, adults and juveniles, in fish killed soon after capture and in animals adapted to laboratory conditions. As far as we are aware, this is the first record of such structures in lower vertebrates.

Animals↗
PubMed1987

The effect of grinding conditions on the toxicity of cobalt-chrome-molybdenum particles in vitro.

Powders of cobalt-chrome-molybdenum alloy were produced by grinding larger particles for 8 h in water, serum or joint fluid. They were administered, in low doses (0.05-0.5 mg/ml) for 1-6 d, to human dermal fibroblasts in vitro. Particles were ground in a biological fluid in order to simulate conditions in an artificial hip joint. Such particles adhered to, or were phagocytosed by, the cells far less than those ground in water. The toxicity of the alloy was linked with a failure of test cells to grow as quickly as the controls - particles ground in water were the most toxic.

Alloys↗
PubMed1986

The histology of tendon attachments to bone in man.

Based on a parallel study of a wide range of human tendons from embalmed dissecting room subjects and from a study of dried bones, an explanation is offered for the well known similarity in gross appearance between the markings left by certain tendons (e.g. those of the rotator cuff) and by articular surfaces on dried bones. Epiphyseal tendons leave markings on bones that look like those left by articular surfaces. These tendons have a prominent zone of fibrocartilage at their attachment site and the deepest part of this is calcified, just as the deepest part of articular hyaline cartilage is calcified. After maceration of the soft tissues, the calcified (fibro) cartilage is left attached to the bone at articular surfaces and at the sites of tendon attachment. In all cases, the tissues separate at the basophilic tidemark between the calcified and uncalcified regions. This tidemark is smooth where there is much overlying uncalcified (fibro) cartilage and it is the smoothness that gives the typical appearance of the dried bone. Blood vessels do not generally traverse the tendon fibrocartilage plugs. Hence the areas are devoid of vascular foramina. The functional significance of tendon fibrocartilage is discussed with particular reference to supraspinatus. It is suggested that the uncalcified fibrocartilage ensures that the tendon fibres do not bend, splay out or become compressed at a hard tissue interface, and are thereby offered some protection from wear and tear. It is also suggested that the fibrocartilage plug of supraspinatus prevents the tendon from rubbing on the head of the humerus.

Aged↗
PubMed1985

A dissecting aneurysm in the bulbus arteriosus of a brook stickleback, Culaea inconstans.

In the bulbus arteriosus of an adult, male brook stickleback, C. inconstans, one of 100 caught in July 1982 from Lake 200, near Erickson, Manitoba, Canada, there was a dissecting aneurysm similar to those in the human aorta. The vessel also showed the classic signs of Erdheim's "idiopathic cystic medionecrosis", but its lumen was dilated and the lesion could thus also be regarded as a fusiform aneurysm. In the proximal half of the bulbus the endothelial lining was torn transversely and blood had extended into the middle layer of the wall to create 2 concentric and longitudinal channels which re-entered the lumen distally at approximately the mid-point of the bulbus. Except near the bulbar-aortic junction, the amount of elastica and (probably) smooth muscle was drastically reduced, the wall was infiltrated with amorphous deposits of mucoid substances, there were focal, cyst-like areas, and the normally tall and intensely PAS-positive, endothelial cells were flattened and poorly staining. There was no evidence of cystic medionecrosis in the bulbus arteriosus of other fish without dissecting aneurysms. This is thought to be the first report of a dissecting aneurysm in any lower vertebrate. Evidently, such an aneurysm can occur in a vessel without vasa vasorum, and in a very small animal (48 mm long), where the wall tension in its blood vessels must be extremely low compared with that in the human aorta.

Aortic Dissection↗
PubMed1985

Experimental studies on cysts in the prolactin zone of the pituitary in the 9-spined stickleback, Pungitius pungitius L.

The incidence of pituitary cysts in the prolactin zone of the stickleback, P. pungitius, cannot be reduced, either compared with laboratory controls or with wild fish, by keeping animals in conditions of minimal osmotic stress (1/3 strength SW). As there were no signs of cyst repair in any animal and as previous attempts to reduce cyst incidence also failed, it is likely that animals with cysts cannot lose them. The study also showed that keeping fish in captivity and handling them each day can induce cysts to appear in the pituitary. Records of fish mortality and the number of cysts per gland and their size and locularity suggest that animals with large cysts (greater than 70 micron in diameter) survive better in 1/3 strength SW and that the factors causing cysts to appear in the pituitary may not be those that induce them to enlarge.

Animals↗
PubMed1985

Lay obligations in professional relations.

Little has been written recently about the obligations of lay people in professional relationships. Yet the Code of Medical Ethics adopted by the American Medical Association in 1847 included an extensive statement on "Obligations of patients to their physicians'. After critically examining the philosophical foundations of this statement, I provide an alternative account of lay obligations in professional relationships. Based on a hypothetical social contract and included in a full specification of professional as well as lay obligations, this account requires lay people to honor commitments and disclose relevant information. Ethically, the account assumes that all parties in lay-professional relationships should be given equal consideration and respect in determining rights and obligations. Factually, it assumes that the treatment of many illnesses and injuries required collaboration and cooperation among lay persons and health professionals, that medical resources and personnel are limited, and that medicine, nursing, and related health professions, are, in MacIntyre's sense, practices.

American Medical Association↗
PubMed1985

Computed tomography of parosteal osteosarcoma.

Twelve patients with parosteal osteosarcomas were evaluated by computed tomography (CT). CT accurately defined the extent of the tumors for purposes of surgical planning, although tumor bone often could not be distinguished from thickened host bone. Nine tumors invaded the medullary cavity, a feature that implies a poorer prognosis when the tumor also contains high-grade areas. Six CT studies accurately detected the medullary invasion, but three did not. Lucent areas within dense tumors contained either benign tissue or high- or low-grade tumor; CT did not differentiate among these different tissues. CT also did not reveal small satellite nodules of tumor beyond the main tumor mass.

Adolescent↗
PubMed1984

Shared parenting: an empirical analysis utilizing a large data base.

The shared parenting literature is replete with rhetoric and relatively bereft of empirical data. In an effort to redress the balance, this study presents the preliminary results of the questionnaire responses of 201 parents involved in a shared parenting arrangement. The findings are presented in six substantive areas. Discussion of these results stresses the viability of shared parenting as a custody option and the need to differentiate carefully between those for whom shared parenting is an appropriate custody option and those for whom it is contraindicated.

Adolescent↗
PubMed1983

A 3-year cytogenetic survey of 9 661 patients in South Africa.

During the period 1 January 1977 - 31 December 1979, 9 661 patients underwent cytogenetic investigation at seven participating laboratories in South Africa. The chromosome data were coded using a standard protocol and the results tabulated, being listed according to the clinical signs which led to referral for investigation. Cytogenetic investigation was most commonly requested for prenatal studies, and 22% of the group's effort was directed towards this. One in 27 amniotic cell specimens was reported to have shown anomalous chromosomes, trisomy 21 being the most frequent abnormality. The majority of postnatal investigations were requested because congenital abnormalities suggested an underlying chromosomal defect. In 42,3% of 2 420 patients a chromosome defect was confirmed. Results of chromosome studies are tabulated by indication for referral and the findings summarized. This collaborative study gives an indication of the nature and frequency of chromosome disorders in South Africa.

Chromosome Aberrations↗
PubMed1982

The ACTH cells in the pituitary gland of the nine-spined stickleback, Pungitius pungitius L.

The ACTH cells form a layer 1-8 cells thick, dorsal to the prolactin cells in the rostral pars distalis. They react only mildly with a variety of stains including PAS-lead haematoxylin. Their nuclear diameters vary seasonally in a manner that closely parallels that of the prolactin cells. The relative volumes of the ACTH and prolactin cell zones are remarkably constant in animals of different sizes. It is suggested that the two hormones may act synergistically at various body sites and that this accounts for the related morphological features of the ACTH and prolactin cells. There are no changes in the surface density of the ACTH zone with increasing animal size. Consequently, the ACTH/neurohypophysial border is highly convoluted in large animals. The proximity of the neurohypophysis also influences cell ultrastructure, as small processes, packed with secretory granules are more numerous near the basal lamina separating the adeno- and neurohypophyses. A morphometric analysis of ACTH cells provides base-line ultrastructural data for experimental studies and for comparisons with other teleosts. The cells have small, secretory granules, 100-300 nm in diameter, and of variable electron density. There is little rough endoplasmic reticulum and a small Golgi apparatus. There is no evidence of granule release by exocytosis and various explanations for this are suggested.

Adrenocorticotropic Hormone↗