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Biomedical subjects

J M Shaw

Publications and source records attributed to J M Shaw.

At least 19 recordsLinked to original sources
PubMed2006

Adaptations in cortical and trabecular bone in response to mechanical loading with and without weight bearing.

Exercise that imparts rapid, high-magnitude mechanical loading is considered to be advantageous to bone health. Previous rodent studies have suggested that swimming may also be beneficial to bone. We investigated the differential effects of exercise with and without weight bearing on cortical and trabecular bone. Forty female Sprague-Dawley rats (120 days) were weight-stratified and randomized into four groups: swim control (Cs, n = 10), swim (S, n = 10), treadmill control (Ct, n = 10), and treadmill (T, n = 10). Treadmill speed was adjusted to match the average limb loading frequency used for swimming, and all training progressed to 1 hour/day, 5 days/week, for 12 weeks. Femurs and humeri were assessed for cortical morphometry by peripheral quantitative computed tomography, areal bone mineral density (BMD) by peripheral dual-energy X-ray absorptiometry, mineral content by ashing, strength by three-point bending, and trabecular volume (BV/TV) by micro-computed tomography. Swimming was associated with increases in cortical thickness and BMD in the humerus midshaft and trabecular BV/TV in the distal femur and proximal humerus compared with age-matched controls. Compared to swimming, treadmill training was associated with increases in percent ash of the femur and humerus and Young's modulus of the femur. Swimming appears to engender novel bone strains and osteogenic adaptations in the humerus and femur, which are different from those induced by normal cage activity. In summary, our findings suggest that when limb loading frequency is matched, swimming may afford greater benefits to cortical and trabecular bone than uphill treadmill work in rats.

Absorptiometry, Photon↗
PubMed2006

Hydatid disease of the liver.

Echinococcus granulosus remains a clinical problem in sheep and subsistence farming communities in South Africa. The most commonly affected organs are the liver and the lung. Most cysts remain clinically silent and are diagnosed incidentally or when complications occur. Clinical examination is unreliable in making the diagnosis. Serological testing has a broad range of sensitivity and specificity and is dependent on the purity of the antigens utilised. Ultrasound examination of the abdomen is gens utilised. Ultrasound examination of the abdomen is both sensitive and cost effective. Computed tomography and endoscopic retrograde cholangiopancreatography (ERCP) are reserved for complicated cases. The differential diagnosis includes any cystic lesion of the liver. Liver hydatid cysts can be treated by medical or minimally invasive (laparoscopic and percutaneous) means or by conventional open surgery. The most effective chemotherapeutic agents against the parasite are the benzimidazole carbamates, albendazole and mebendazole. Albendazole is more efficacious, but recommended treatment regimens differ widely in terms of timing, length of treatment and dose. Medical treatment alone is not an effective and durable treatment option. PAIR (puncture, aspiration, injection, reaspiration) is the newest and most widely practised minimally invasive technique with encouraging results, but it requires considerable expertise. Open surgery remains the most accessible and widely practised method of treatment in South Africa. The options are either radical (pericystectomy and hepatic resection) or conservative (deroofing and management of the residual cavity). Various scolicidal agents are used intraoperatively (Eusol, hypertonic saline and others), although none have been tested in a formal randomised controlled trial. Laparoscopic surgery trials are small and unconvincing at present and should be limited to centres with expertise. Complicated cysts (intrabiliary rupture and secondary infection) may require ERCP to obtain biliary clearance before surgery, and referral to a specialist centre may be indicated.

Animal Husbandry↗
PubMed2005

The evolving role of endoscopic treatment for bleeding esophageal varices.

The treatment of acute and recurrent variceal bleeding is best accomplished by a skilled, knowledgeable, and well-equipped team using a multidisciplinary integrated approach. Optimal management should provide the full spectrum of treatment options including pharmacologic therapy, endoscopic treatment, interventional radiologic procedures, surgical shunts, and liver transplantation. Endoscopic therapy with either band ligation or injection sclerotherapy is an integral component of the management of acute variceal bleeding and of the long-term treatment of patients after a variceal bleed. Variceal eradication with endoscopic ligation requires fewer endoscopic treatment sessions and causes substantially less esophageal complications than does injection sclerotherapy. Although the incidence of early gastrointestinal rebleeding is reduced by endoscopic ligation in most studies, there is no overall survival benefit relative to injection sclerotherapy. Simultaneous combined ligation and sclerotherapy confers no advantage over ligation alone. A sequential staged approach with initial endoscopic ligation followed by sclerotherapy when varices are small may prove to be the optimal method of reducing variceal recurrence. Overall, current data demonstrate clear advantages for using ligation in preference to sclerotherapy. Ligation should therefore be considered the endoscopic treatment of choice in the treatment of esophageal varices.

Endoscopy, Gastrointestinal↗
PubMed2004

Diagnostic laparoscopy and diverting sigmoid loop colostomy in the management of civilian extraperitoneal rectal gunshot injuries.

BACKGROUND: This prospective study reviews the management of isolated civilian extraperitoneal rectal gunshot injuries using a protocol of diagnostic laparoscopy and abdominal wall trephine diverting loop colostomy, without laparotomy, distal rectal washout and presacral drainage. METHODS: Patients admitted to the trauma unit at Groote Schuur Hospital between January 2000 and December 2002 with a rectal injury were evaluated. A rectal injury was confirmed by digital rectal examination and proctosigmoidoscopy. Missile peritoneal violation was excluded by diagnostic laparoscopy. Normal laparoscopy was followed by creation of a diverting sigmoid loop colostomy through an abdominal wall trephine, without a laparotomy. No distal rectal washout or presacral drainage was performed. RESULTS: Of the 104 patients admitted with 106 rectal injuries, 20 (19.2 per cent) qualified for inclusion in the study. All had sustained low-velocity gunshot injuries of which 18 exhibited a transpelvic trajectory. Diagnostic laparoscopy was normal and a trephine diverting loop sigmoid colostomy was performed in all 20 patients. No pelvic sepsis occurred. Two patients developed rectocutaneous fistulas, both of which resolved without surgical treatment. Nineteen stomas have since been closed. CONCLUSION: Low-velocity gunshot injuries isolated to the extraperitoneal rectum can be managed safely by laparoscopic exclusion of intraperitoneal missile penetration and diverting sigmoid loop colostomy, without laparotomy, distal rectal washout or presacral drainage

Adolescent↗
PubMed2004

Preclinical evaluation of a prostate-targeted gene-directed enzyme prodrug therapy delivered by ovine atadenovirus.

Gene-directed enzyme prodrug therapy (GDEPT) based on the Escherichia coli enzyme, purine nucleoside phosphorylase (PNP), provides a novel strategy for treating slowly growing tumors like prostate cancer (CaP). PNP converts systemically administered prodrug, fludarabine phosphate, to a toxic metabolite, 2-fluoroadenine, that kills PNP-expressing and nearby cells by inhibiting DNA, RNA and protein synthesis. Reporter gene expression directed by a hybrid prostate-directed promoter and enhancer, PSMEPb, was assayed after plasmid transfection or viral transduction of prostate and non-CaP cell lines. Androgen-sensitive (AS) LNCaP-LN3 and androgen-independent (AI) PC3 human CaP xenografts in nude mice were injected intratumorally with an ovine atadenovirus vector, OAdV623, that carries the PNP gene under PSMEPb, formulated with cationic lipid for enhanced infectivity. Fludarabine phosphate was then given intraperitoneally for 5 days at 75 mg/m2/day. PNP expression was evaluated by enzymic conversion of its substrate using reverse phase HPLC. OAdV623 showed excellent in vitro transcriptional specificity for CaP cells. In vivo, expression of PNP persisted for > 6 days after OAdV623 injection and a single treatment provided 100% increase in tumor doubling time and > 50% inhibition of tumor growth for both LNCaP-LN3 and PC3 lines, with increased tumor necrosis and apoptosis and decreased tumor cell proliferation. OAdV623 significantly suppressed the growth of AS and AI human CaP xenografts in mice.

Adenine↗
PubMed2004

Influence of hormone environment and donor age on cryopreserved common wombat (Vombatus ursinus) ovarian tissue xenografted into nude mice.

Developmentally competent oocytes can be collected from xenografted ovarian tissues; however, optimal xenograft conditions need to be established for this technique to be of use in assisted reproduction. In the present study, common wombat ovarian tissue was xenografted under the kidney capsule of nude mice to clarify the role of recipient gonadal status and donor tissue age on graft establishment, follicle development and oocyte recovery. Eighty-nine per cent of all grafts were recovered; of these, 78% contained growing follicles. In female graft recipients, follicle development to the antral stage occurred earlier in ovariectomised recipients compared with intact graft recipients. Similarly, follicle development occurred earlier in recipients of pouch young ovarian tissue grafts when compared with subadult xenografts. Follicle development proceeded to the antral stage in subadult grafts placed under the kidney capsule of male recipient mice, albeit at a slower rate than subadult grafts placed in female recipients. Oocytes were collected from grafts placed in female and male recipients, but no mature oocytes were observed at the time of collection, nor could these oocytes be matured in vitro. The present study demonstrated that common wombat pouch young tissue xenografted to female recipient mice, and subadult ovarian tissue xenografted to male recipient mice, can develop to the antral stage and can therefore facilitate oocyte collection. However, mature oocytes were not obtained using the current protocol.

Age Factors↗
PubMed2002

Comparison of slow- and rapid-cooling protocols for early-cleavage-stage Macaca fascicularis embryos.

Cryostorage of nonhuman primate embryos by time-consuming slow-cooling methods is often limited to early cleavage stages. Effective rapid-cooling methods have been developed for many species and represent valuable tools for laboratory- and field-based studies of nonhuman primate reproductive biology. However, few rapid-cooling protocols have been applied to nonhuman primate embryos in terms of comparing various developmental stages. Here we compare slow cooling vs. two- and three-step rapid cooling of two-, four-, and eight-cell Macaca fascicularis (Mf) embryos. Rapid cooling was conducted in open pulled straws (OPS) using cooling solutions containing reduced quantities of ethylene glycol (EG) and supplemented with either of two high-molecular-weight polymers, ficoll and dextran. The survival of the slow-cooled embryos, but not the rapid-cooled embryos, was independent of embryonic stage at cryostorage. Slow cooling was associated with greater cell survival (82%) post thaw compared to warming following rapid cooling (18-29%). Slow cooling resulted in a high proportion of embryo survival (18/20; 90%) and cleavage (15/18; 83%) post thaw. Rapid cooling resulted in significantly reduced percentages of embryo survival (26-32%) and embryo cleavage in culture (29-38%) after warming. Conventional slow cooling was more effective than the rapid-cooling protocols employed in this study for cryopreservation of early-cleavage-stage Mf embryos.

Animals↗
PubMed2002

Structure and expression of the follicle-stimulating hormone receptor gene in a marsupial, Macropus eugenii.

Follicle stimulating hormone (FSH) is essential for folliculogenesis. The function of FSH is mediated through its receptor (FSHr) and modulation of the receptor is thought to be the mechanism by which the responsiveness of follicles to gonadotrophins is regulated. FSHr is alternatively spliced to produce several transcripts in all eutherian species studied. However, controversy exists over the significance of alternatively spliced transcripts. In this study, we cloned and characterised the tammar wallaby (Macropus eugenii) FSHr gene and examined its expression. Comparison of gene structure and function between marsupials and eutherians enables identification of conserved features that are likely to be of functional significance. Tammar FSHr shares 94% amino acid similarity with human FSHr and is expressed in both the adult testis and ovary suggesting a similar function for this gene in both marsupials and eutherians. Tammar FSHr undergoes alternate splicing to produce four transcripts consistent with the splice variants seen in eutherians. These results strongly suggest that alternate splicing is of functional significance in the ovary since it has remained a highly conserved character of this gene for over 100 million years of divergent evolution.

Amino Acid Sequence↗
PubMed2002

Bone mineral density of competitive male mountain and road cyclists.

The purpose of this study was to compare the bone mineral density (BMD) of two types of trained male cyclists (n = 30) with recreationally active men (n = 15), aged 20-40 years. Sixteen of the cyclists regularly trained for, and competed in, cross-country mountain bike races. The other 14 cyclists trained and raced on the road. The cyclists had trained an average of 11 +/- 3 hours per week for 8 +/- 4 years. Fifteen recreationally active men volunteered as controls. Dual-energy X-ray absorptiometry (DXA) was used to assess BMD of the proximal femur, lumbar spine, and total body. Anthropometric, muscle strength and power, aerobic fitness, and sex hormone data assessments were conducted on all participants. Mountain cyclists were younger and weighed less than road cyclists and controls. BMD at all sites was comparable among the three groups (p > 0.05). When adjusted for body weight and controlled for age, BMD was significantly higher at all sites in the mountain cyclists compared with the road cyclists and controls. Some anthropometric, physical fitness, and sex steroid variables were predictive of BMD, but of these variables, only total body weight, total body fat, and aerobic fitness were different between the groups. In conclusion, endurance road cycling does not appear to be any more beneficial to bone health than recreational activity in apparently healthy men of normal bone mass. Higher BMD in the mountain cyclists suggests that mountain cycling may provide an osteogenic stimulus that is not inherent to road cycling.

Adult↗
PubMed2002

Experimental models for ovarian tissue and immature follicles.

Primordial and growing follicles are abundant within the ovaries of healthy young female mammals. While our understanding of follicular dynamics is based mainly on studies of normal ovaries in intact animals, techniques such as ovarian grafting and in vitro culture, in particular when used in combination with cryopreservation, have provided both significant additional insights and a source of mature oocytes. Primordial follicles are small, quiescent, and most commonly located within the collagen-rich outer portion of the ovary. Providing that appropriate collection, handling, freezing, and thawing methods are used, they can tolerate cryopreservation very well irrespective of whether they are frozen within a whole ovary (small species), as ovarian pieces, or as individual, isolated, follicles. Animal studies show that grafts of such fresh or frozen materials can, providing that they contain viable follicles, form mature fertilizable oocytes, produce hormones, and support pregnancies to term. Grafts can be returned to the original donor (autograft), but grafting between histocompatible individuals of the same species and between species (xenografts) is also possible. Cryopreservation and grafting are therefore useful both as practical and as experimental tools. Clinically, ovarian tissue has started to be collected and frozen for patients who are at risk of ovarian failure. Very recent case reports show that such frozen ovarian tissue autografts can support the return of menses and antral follicle formation in patients, although as yet no pregnancies have been established.

Animals↗
PubMed2002

Influence of donor age on development of gonadal tissue from pouch young of the tammar wallaby, Macropus eugenii, after cryopreservation and xenografting into mice.

Ovaries from a marsupial, the tammar wallaby (Macropus eugenii), were grafted into a eutherian recipient at known stages of development to ascertain whether normal development would occur. Xenografted ovaries from pouch young < 20 days old, before the onset of meiosis, retained few germ cells and developed tubule-like structures reminiscent of seminiferous cords. Ovaries from 50-day-old pouch young, which contain primordial follicles, developed into antral follicles and corpora lutea within the eutherian host, and produced hormones that stimulated the reproductive tract of the host. The timing of onset of antrum formation and the progress of follicle development were advanced relative to the timing of events in ovaries in situ. Frozen-thawed ovaries from 50-day-old donors developed into preantral follicles, but at a reduced rate and number. This finding shows that gonads of a marsupial species can develop as xenografts in a eutherian, forming large antral follicles. Accelerated follicular development in xenografts provides a potentially valuable model for studying the factors that control follicle development. Assisted reproduction of endangered marsupials may also be feasible using follicles from pouch young grown as xenografts in a eutherian host.

Aging↗
PubMed2001

Defining the repeating elements in the cysteine-rich region (CRR) of the CD18 integrin beta 2 subunit.

The cysteine-rich region (CRR) of the integrin beta subunits is organised into four repeating elements. By expression of a panel of truncated beta 2 subunits, and CRR segments fused to the C-terminal end of a CD4 soluble fragment, the segment required for the expression of two monoclonal antibody conformational epitopes was determined. This segment, E482-Q574, contains 16 cysteines representing two repeating units. We have thus defined the CRR unit motif of 'xC---C---C---CxCxxCxC---Cx', where 'x' represents a single residue, and '---' represents a stretch of four to 14 residues.

Amino Acid Sequence↗
PubMed2001

The N-terminal region and the mid-region complex of the integrin beta 2 subunit.

In the primary sequence of the integrin beta subunit, the N-terminal region (NTR) and mid-region are separated by the I-like domain. To determine the spatial relationship and functional properties of the integrin beta(2) NTR and mid-region, we constructed beta(2)/beta(7) chimeras in which the NTR, I-like domain, and the mid-region of the beta(2) subunit were replaced by those of beta(7). Changing either the beta(2) NTR or mid-region, but not the I-like domain to that of beta(7) did not affect LFA-1 (alpha(L)beta(2)) formation and surface expression. Thus, the specificity of alpha(L)beta(2) pairing is conferred by the I-like domain but not the NTR or mid-region. Using these chimeras, the epitopes of six anti-beta(2) mAbs (H52, 7E4, AZN-L18, AZN-L27, KIM202, and MEM-148) were mapped. All except H52 require both the NTR and mid-region for epitope expression. Since these mAbs have distinct properties in terms of epitope expression and effect on LFA-1 binding to ICAM-1, we conclude that the beta(2) NTR and mid-region interact extensively. Although the I-like domain is located between the NTR and mid-region, its removal does not affect the folding of the beta(2) NTR/mid-region complex because this complex alone can be expressed as a soluble protein and precipitated by the appropriate mAbs. Finally, the mAbs H52 and 7E4, abrogated KIM185- but not Mg/EGTAinduced LFA-1/ICAM-1 binding and the epitope of MEM-148 is expressed on Mg/EGTA-activated but not resting LFA-1. These results suggest that the NTR/mid-region complex is involved in the regulation of LFA-1 function.

Amino Acid Sequence↗
PubMed2001

Yeast vectors for integration at the HO locus.

We have constructed new yeast vectors for targeted integration of desired sequences at the Saccharomyces cerevisiae HO locus. Insertion at HO has been shown to have no effect on yeast growth, and thus these integrations should be neutral. One vector contains the KanMX selectable marker, and integrants can be selected by resistance to G418. The other vector contains the hisG-URA3-hisG cassette, and integrants can be selected by uracil prototrophy. Subsequent growth on 5-FOA permits identification of colonies where recombination between the hisG tandem repeats has led to loss of the URA3 marker and return to uracil auxotrophy. We also describe several new bacterial polylinker vectors derived from pUC21 (ampicillin resistance) and pUK21 (kanamycin resistance).

Ampicillin Resistance↗
PubMed2001

Follicular development in cryopreserved Common Wombat ovarian tissue xenografted to Nude rats.

The Northern Hairy-nosed Wombat (Lasiorhinus krefftii) is a highly endangered marsupial species and every possible option for sustaining the species needs to be explored. One important approach may be the development of assisted reproductive technologies in the non-endangered Common Wombat (Vombatus ursinus) and Southern Hairy-nosed Wombat (Lasiorhinus latifrons) for application in breeding the Northern Hairy-nosed Wombat. In this study, it was examined whether cryopreserved Wombat ovarian tissue would develop following xenografting to immunologically deficient rats. Ovarian tissue was collected from Common Wombats (n = 3) and cryopreserved as small cortical pieces. After thawing the cortical pieces were grafted underneath the kidney capsule of Nude rats (n = 16). The grafts were recovered at 2, 4, and 10 weeks after transplantation and their gross and histological appearance investigated. Two weeks after grafting (n = 2), the tissue was revascularized and healthy primordial follicles were present. At week 4 (n = 2), some follicular development was present. At week 10, six rats received human chorionic gonadotrophin (hCG) to trigger follicle and oocyte maturation while another six rats were not given any treatment. The administration of hCG did not induce preovulatory follicles and oocyte maturation although type 5 follicles were present in ovarian tissue collected 10 weeks posttransplantation in both treated and untreated groups. This study demonstrates for the first time that Wombat ovarian tissue can survive and function when grafted into immunocompromized rats and that Wombat ovarian follicles can be recruited to growth and development in an ovarian xenograft. This model system has the potential to produce mature oocytes from endangered species for use in assisted reproductive technologies such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and mature oocytes from non-endangered species for nuclear transfer which may be necessary for the preservation of critically endangered species.

Animals↗
PubMed2001

Studies on replacing most of the penetrating cryoprotectant by polymers for embryo cryopreservation.

Solutions used for vitrification or rapid cooling of embryos usually contain high concentrations of penetrating cryoprotectants. At these concentrations embryos can tolerate the penetrating cryoprotectants for only short periods of time without damage. This study designed and tested cryoprotectant solutions that combined high polymer concentrations with low penetrating cryoprotectant concentrations. Mouse 2-cell embryo development was not compromised by up to 15-min exposure to 30 wt% solutions of the polymers Ficoll 70,000 MW or dextran 69,000 MW at room temperature. However, our batches of polyvinylpyrrolidone (PVP) 10,000 and PVP 40,000 were embryo-toxic even after extensive dialysis against Milli-Q water. As both Ficoll and dextran contribute to a solution's physical vitrification properties, we formulated vitrifying solutions containing only 11 to 27 wt% ethylene glycol (EG) by including 34 to 49 wt% polymers (27 wt% EG + 34 wt% Ficoll, 27 wt% EG + 34 wt% dextran, 16 wt% EG + 39 wt% Ficoll, or 11 wt% EG + 49 wt% Ficoll, in phosphate-buffered saline (PBS)). Novel solutions were designed for 0.25 ml straw as a viscous matrix for encapsulation of embryos. These yielded high rates of development of 2-cell mouse embryos after rapid cooling and warming (> or = 96% expanded blastocysts in vitro and > or = 62% viable fetuses as assessed on day 15 of gestation in vivo) in all tested solutions. All control 2-cell embryos formed expanded blastocysts in vitro and 78% formed fetuses in vivo. Comparable results were obtained with both 4-cell and 8- to 16-cell mouse embryos. The lower toxicity of Ficoll and dextran may explain why these new solutions gave better results than had previously been reported for solutions containing 7.5% PVP and low concentrations of EG (2 M).

Animals↗