The fate of experimental organ-cultured corneal xenografts

Human, chicken, and guineapig corneas organ cultured (O.C.) from 1 to 4 weeks were transplanted intralamellarly into rabbits. Chicken and guinea pid corneal xenografts O.C 3 to 4 weeks had statistically significant delayed rejection times reject. Histologically, O.C. xenografts with delayed rejection or nonrejection were hypocellular. Chicken xenografts O.C. 4 weeks in which recipient (autochthonous) rabbit serum replaced the calf serum routinely used in the media also had a significant delay in rejection time when compared to fresh controls or chicken xenografts stored in pooled (allogeneic) rabbit serum. The rejection time of human corneal xenografts O.C. FOR PERIODS UP TO 4 WEEKS WAS NOt delayed. These data suggest that in this model, prolonged survival of xenografts after O.C. is species specific and represents a form of immunological modification, possibly reduced antigenicity sedondary to donor hypocellularity.

A metabolic and electron microscopic study of human organ-cultured cornea

We examined the glucose metabolism and ultrastructure of human corneas stored for 11 to 37 days in organ culture using a modified Eagle's minimum essential medium. Changing the media twice weekly provided a stable pH of 7.22 to 7.28 but the glucose concentration of the media decreased from 110 mg/100 ml to 30 mg/100 ml, and lactate concentration increased from 7 mg/100 ml to 84 mg/100 ml before media replacement. The initial rate of glucose uptake and lactate release averaged 149 mug/hr and 95 mug/hr, respectively, and the rates decreased approximately 50% by day 12. The glucose uptake rate stabilized between 40 and 60% of the original rate to day 37, but the lactate release rate decreased again at day 25 from 64 to 25%. The lactate/glucose ratio averaged 65 to 82% during the first 25 days of organ culture and 33 to 53% from days 28 to 37. Electron microscopy revealed that the endothelium formed a complete monolayer of normal appearing cells covering Descemet's membrane. Intracytoplasmic deposition of glycogen granules was present in endothelial, stromal, and epithelial cells.

Undergraduate grades, class standings, and performance in a graduate orthodontics curriculum

This study shows that graduate performance correlates poorly with undergraduate class standing; that relatively large differences in class standing are not generally accompanied by correspondingly large differences in grade point average; and that performance in just ten courses, taken in the freshman and sophomores years, predicts, with a multiple correlation coefficient of 0.88, the final undergraduate class ranking of a student. It is argued that variables other than class rank should receive more weight in the selection of graduate dental students. Undergraduate orthodontics courses made no significant contribution to this prediction. These factors, when combined with a failure to include other relevant factors in selecting graduate students (in particular, the failure to take into account any postgraduate clinical experience), explain the low correlation between undergraduate class rank and performance in the graduate orthodontics program. It is suggested therefore that factors other than undergraduate class rank receive considerably more weight in the selection process.

Development of specific nonreactivity in human cadaveric renal allograft recipients

The development of specific nonreactivity and mixed leukocyte culture blocking factor activity (MLC-BFA) was serially studied in three cadaveric renal allograft recipients. All patients developed hypo and/or nonreactivity in the MLC reaction to the specific donor but not to an indifferent donor. Specific hypo and/or nonreactivity observed in the MLC reaction was independent of recipient's response to PHA which remained normal. Broad reacting MLC-BFA declined and subsequently disappeared after the state of specific nonreactivity was achieved. Several allograft rejection crisis occurred during the active stage, but these crises subsided once the nonreactivity was achieved.

Lymphocyte transformation in human plasma without addition of synthetic medium. A study of immune function in patients with chronic uraemia or diabetes mellitus

The in vitro response of lymphocytes obtained from normal subjects, uraemic patients on haemodialysis and diabetic patients was studied using cultures containing either medium plus plasma (medium cultures) or plasma alone (plasma cultures). The study demonstrated that plasma alone can adequately support lymphocyte transformation induced by nonspecific mitogens (PHA and PWM) and allogeneic lymphocytes in mixed lymphocyte culture (MLC) reaction. This investigation further confirms our previously reported findings that uraemic patients undergoing haemodialysis have a normal lymphocyte response in MLC and to PHA and PWM. Plasma cultures give results similar to conventional medium cultures in subjects where lymphocyte transformation is normal. The lymphocyte hyporactivity observed in diabetics is, however, better shown in the plasma cultures. The suppressed response of the diabetic patient's lymphocytes to PHA and PWM both in the presence of autologous and normal AB plasma suggests intrinsic lymphocyte dysfunction as the explanation for impaired immune function. Plasma cultures may provide a better in vitro system for the evaluation of immune function in certain groups of patients where it is desirable to distinguish between intrinsic abnormalities of lymphocyte function and the effect of humoral immunosuppressive factors.

Mixed leucocyte culture blocking factor activity in allograft recipients and its role in the clinical outcome of human cadaveric renal allografts

Seventeen renal allograft recipients were followed serially both pre- and post-transplantation for the presence of mixed leucocyte culture blocking factor activity (MLC-BFA) in their plasma. Patients could be divided into three distinct groups on the basis of MLC-BFA and lymphocytotoxin (LT) determinations. Fifteen out of seventeen patients possessed MLC-BFA at one time or another while four out of seventeen were positive for LT. Four patients of group 1 with pre-transplant LT and MLC-BFA rejected their grafts within 1 year. Two LT negative patients of group 2 developed no detectable MLC-BFA during a follow-up period of over 1 year. One other patient developed MLC-BFA 8 months following transplantation. All three patients had an excellent clinical course. Ten patients belonging to group 3 possessed no LT or MLC-BFA prior to transplantation but developed MLC-BFA alone after receiving an allograft. Only one patient rejected his allograft within 2 months. The remaining nine patients experienced mild rejection crises during the first 3 months after transplantation but had excellent renal function at 1 year or beyond that time. Our results indicate that MLC-BFA in the presence of LT may not prevent rejection. MLC-BFA is associated with a good clinical course in LT negative patients. However, certain patients who fail to develop LT or MLC-BFA in spite of repeated blood transfusions prior to transplantation may also do extremely well in the absence of detectible MLC-BFA.

Hepatitis B surface antigen (HBsAg) infection in a hemodialysis unit. II. Factors affecting host immune response to HBsAg

Serum from 86 hemodialysis patients, 105 healthy hospital staff "at risk" and 160 regular hospital staff was screened for hepatitis B surface antigen (HBsAg) and antibody (anti-HBs). The combined prevalence of HBsAg and anti-HBs was higher in the staff of the artificial kidney unit (57.7%) than in the hemodialysis patients (33.7%). The healthy subjects with HBsAg infection responded significantly more often by producing anti-HBs compared with the hemodialysis patients. Twelve of 29 (41.4%) hemodialysis patients with HBsAg infection produced anti-HBs, while 17 (58.6%) remained positive for HBsAg. This differential response could not be attributed to age, sex, time spent undergoing hemodialysis, delayed cutaneous reactivity or response to phytohemagglutinin (PHA) or pokeweed mitogen (PWM). However, a much larger proportion of patients with HBsAg than with anti-HBs had previously received blood transfusions (88.2% v. 33.3%). Our results indicate that development of the chronic HBsAg carrier state or production of anti-HBs in uremic patients may be influenced by the route of immunization or the dose of antigen, or both. Although uremic patients maintain normal in vitro response to PHA and PWM, they may have depressed immunity in vivo because of a decreased total number of T-lymphocytes.

The fine structure of the epidermis of two species of salmonid fish, the Atlantic salmon (Salmo salar L.). and the brown trout (Salmo trutta L.)

The fine structure of epidermal mucous cells of two species of salmonid fish has been described. Mucous cells are, next to filament-containing cells, the most commonly encountered cells in fish epidermis. The development of the cells as they progress to the periphery has been characterised. They are initially difficult to distinguish from filament-containing cells: later, they can be recognised by the presence of much smooth-surfaced E.R. The mucigenesis and the subsequent secretion of mucus has been observed and it is essentially comparable to that which occurs in the mucous cells of the mammalian intestine. The mucous layer of the epidermal surface seems to mainly comprise of the products of these mucous cells and the "cuticle" seen in other species has not yet been observed in the salmonid species investigated here.

In vitro reactivity of lymphocytes obtained from uraemic patients maintained by heamodialysis

Lymphocytes obtained from uraemic patients maintained on intermittent haemodialysis had a normal ability to respond to and stimulate allogeneic lymphocytes obtained from normal subjects in the mixed lymphocyte culture (MLC) reaction. The response of these uraemic lymphocytes to PHA and pokeweed mitogen (PWN) was also normal. Uraemic plasma from eight out of twenty-six patients studied, however, possessed blocking factor activity which suppressed the MLC reactivity of normal random donors and also the mitogenic response of allogeneic lymphocytes but not of autologous uraemic lymphocytes. The blocking factor activity was attributed to a non-dialysable factor present in the plasma of the patients investigated.

SNA and SNB angles in a population of Nubian schoolchildren

The descriptive statistics for the sella-nasion-A point (SNA) and sella-nasion-B point (SNB) angles computed from a sample of Nubian schoolchildren are presented, by age and sex, and compared with the analogous statistics for American Caucasian schoolchildren.

Lymphocytotoxins and mixed leucocyte culture blocking factor activity in the plasma of uraemic patients undergoing haemodialysis

Mixed leucocyte culture blocking factor activity (MLC-BFA) in the plasma of haemodialysis patients appears as a result of recent blood transfusions and is concentrated in IgG fractions of the blocking serum. Four patients neither developed lymphocytotoxins nor MLC-BFA in spite of having received multiple blood transfusions. Such 'unresponsive' recipients had an excellent clinical course upon receiving an allograft.

Ultrastructure of human organ-cultured cornea. II. Stroma and epithelium

The stroma and epithelium of human corneas that had been stored in organ culture medium for 10 to 22 days at 37 C were examined by light and electron microscopy. Total corneal thickness was found to be doubled at ten days and there was no further increase even at 22 days. The posterior portion of the stroma was more hydrated than the anterior region. Stromal cells were reduced in number and normal-appearing cells were present only in superficial stroma. The epithelial basement membrane was irregular and thickened. Although the epithelium was reduced to three or four cells in thickness and the intercellular spaces were dilated, the epithelial cells contained normal subcellular organelles and appeared to be viable.